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PC CONTROLLED MILITARY ROBOT USING ZIGBEE
INDEX
CONTENTSAbbreviations
1. Figure Locations2. Introduction to the project3. Block Diagram4. Block Diagram Description5. Schematic6. Schematic Description7. Introduction to GSM and GPS technology8. Hardware Components
Micro controllers ZIGBEE TRANSCEIVER MAX 232 H-BRIDGE(L293D) DC GEARED MOTOR CAMERA LANDMINE SENSOR Power Supply PC
9. Circuit Description10. Software components
a. About Keilb. Embedded ‘C’
11. Source Code12. Conclusion (or) Synopsis13. Future Aspects
14.Bibliography
1
1.Abbreviations:
Microcontroller:
Symbol NameACC Accumulator
B B register
PSW Program status word
SP Stack pointer
DPTR Data pointer 2 bytes
DPL Low byte
DPH High byte
P0 Port0
P1 Port1
P2 Port2
P3 Port3
IP Interrupt priority control
IE Interrupt enable control
TMOD Timer/counter mode control
TCON Timer/counter control
T2CON Timer/counter 2 control
T2MOD Timer/counter mode2 control
TH0 Timer/counter 0high byte
TL0 Timer/counter 0 low byte
TH1 Timer/counter 1 high byte
TL1 Timer/counter 1 low byte
TH2 Timer/counter 2 high byte
TL2 Timer/counter 2 low byte
SCON Serial control
SBUF Serial data buffer
PCON Power control
2
ZIGBEE:
IEEE Institute of electronics and electrical engineers
WPAN Wireless Personal Area Network
AES Advanced encryption standard
FFD Full function device
RFD Reduced function device
LOS Line of sight
CSMA/CA Carrier sense multiple access/collision avoidance
CTS Clear to send
RTS Request to send
DIN Data in
DOUT Data out
UART Universal asynchronous receiver and transmitter
BD Baud rate
CE Coordinator enable
DH-DL Destination high-destination low
SH-SL Serial high-serial low
MY 16-bit source address(my address)
ND Node discover
NI Node identifier
DN Destination node
AC Apply changes
PHY Physical layer
MAC Media access control
APL Application layer
NWK Network layer
ZDO Zigbee device object
AF Application frame
CCA Clear channel assessment
3
2.Figure Locations:
1. Block diagram2. Schematics 3. Network topologies4. Various wireless technologies5. Architecture of AT89C516. Pin description of AT89C517. External clock drive configuration8. Program memory9. Data memory10. 89C51 memory structure11. PSW register12. DB9 connector13. Connection diagram of MAX23214. Transmitter flow chat15. Receiver flow chat16. Pin diagram of MAX23217. Female connector18. Male connector19. Block Diagram of the DC motor20. Block Diagram of the DC motor having two poles only21. Block Diagram of the DC motor having Three poles22. Internal Block Diagram of the Three pole DC motor23. H-bridge24. Zigbee Transceiver 25. Data flow diagram26. Serial data sequence27. Internal data flow diagram 28. NonBeacon Peer-to-Peer Architecture29. Different Modes of Operation30. Syntax for sending AT Commands31. Zigbee Architecture32. LM 7805 regulator IC33. Block diagram of power supply34. Circuit diagram of power supply35. Typical bridge rectifier36. Current flow in bridge rectifier
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3.INTRODUCTION TO EMBEDDED SYSTEMS:
Embedded systems are designed to do some specific task rather than be a general-
purpose computer for multiple tasks.Some also has real time performance constraints that
must be met, for reason such as safety and usability; others may have low or no performance
requirements, allowing the system hardware to be simplified to reduce costs.
An embedded system is not always a separate block - very often it is physically built-
in to the device it is controlling.
The software written for embedded systems is often called firmware, and is stored in
read-only memory or flash convector chips rather than a disk drive. It often runs with limited
computer hardware resources: small or no keyboard, screen, and little memory.
Communication:Communication refers to the sending, receiving and processing of information by
electric means. As such, it started with wire telegraphy in the early 80’s, developing with
telephony and radio some decades later. Radio communication became the most widely used
and refined through the invention of and use of transistor, integrated circuit, and other semi-
conductor devices. Most recently, the use of satellites and fiber optics has made
communication even more wide spread, with an increasing emphasis on computer and other
data communications.
A modern communications system is first concerned with the sorting, processing and
storing of information before its transmission. The actual transmission then follows, with
further processing and the filtering of noise. Finally we have reception, which may include
processing steps such as decoding, storage and interpretation. In this context, forms of
communications include radio, telephony and telegraphy, broadcast, point to point and
mobile communications (commercial and military), computer communications, radar, radio
telemetry and radio aids to navigation. It is also important to consider the human factors
influencing a particular system, since they can always affect its design, planning and use.
In this project “PC controlled military robot using zigbee”, like the title indicates the
controlling action of Robot is done through the PC. The robot is kept some other place and
we can operate the robot by sitting in front of the PC through the 2.4 GHz RF communication
i.e. Zigbee.
5
ZIGBEE is a new wireless technology guided by the IEEE 802.15.4 Personal Area
Networks standard. It is primarily designed for the wide ranging automation applications and
to replace the existing non-standard technologies. It currently operates in the 868MHz band at
a data rate of 20Kbps in Europe, 914MHz band at 40Kbps in the USA, and the 2.4GHz ISM
bands Worldwide at a maximum data-rate of 250Kbps.
The ZIGBEE specification is a combination of Home RF Lite and the 802.15.4
specification. The specification operates in the 2.4GHz (ISM) radio band – the same band as
802.11b, Bluetooth microwaves and some other devices. It is capable of connecting 255
devices per network. The specification supports data transmission rates of up to 250 Kbps at a
range of up to 30 meters. ZIGBEE's technology is slower than 802.11b (11 Mbps) and
Bluetooth (1 Mbps) but it consumes significantly less power.
INTRODUCTION TO PROJECT
Now a day's every system is automated in order to face new challenges. In the present
days Automated systems have less manual operations, flexibility, reliability and accurate.
Due to this demand every field prefers automated control systems. Especially in the field of
electronics automated systems are giving good performance. and we can implement a
system in which a robot direction can be controlled wirelessly with respect to the
commands given by the user through PC using Zigbee technology.
In this project “pc controlled military robot using Zigbee”, like the title indicates that
controlling action of Robot is done through PC and a new wireless technology called
“Zigbee”. This project is to design a robotic system for military applications using zigbee
technology. Here in this project robot is controlled through PC.
Zigbee is a new wireless technology guided by IEEE 802.15.4 Personal Area Network
standard. And can communicate with 2.4GHZ
In transmitter, the microcontroller will route the notice to receiver using Zigbee
transceiver and in receiver side the received notice is going to display in LCD.
6
4.BLOCK DIAGRAM:
TRANSMITTER SECTION:
7
MICRO CONTROLLER
MAX-232
PC
ZIGBEETRANSCEIVER
POWER SUPPLY
LCD
RECEIVER SECTION:
H-BRIDGE
5.BLOCK DIAGRAM EXPLANATION:
This Project mainly consists of Power Supply section, Microcontroller section, Zigbee transreceiver, H-bridge, dc motor ,PC and Max-232.
Micro controller:
In this project work the micro-controller is plays major role. Micro-controllers were originally used as components in complicated process-control systems. However, because of their small size and low price, Micro-controllers are now also being used in regulators for individual control loops. In several areas Micro-controllers are now outperforming their analog counterparts and are cheaper as well.
MAX- 232
To allow compatibility among data communication equipment made by various manufactures, an interfacing standard called RS232 was set by the Electronic Industries Association (EIA). This RS-232 standard is used in PCs and numerous types of equipment .However, since the standard was set long before the advent of the TTL logic family, its input and output voltage levels are not TTL compatible. In RS-232 ,a 1 is represented by -3 to -25V,while a 0 bit is +3 to +25V,making -3 to +3 undefined. For this reason, to connect any RS-232 to a microcontroller system we must use voltage converters such as MAX232 to convert the TTL logic levels to the RS-232 voltage levels and vice versa.
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MICRO CONTROLLER
ZIGBEETRANSCEIVER
POWER SUPPLY
MOTOR
MOTOR DRIVER
So here we are using this MAX-232 to have compatibility between the GSM MODEM and microcontroller. ZIGBEE:
Zigbee is new wireless technology guided by IEEE 802.15.4 Personal Area Network
standard. It is primarily designed for the wide ranging controlling applications and to
replace the existing non-standard technologies. It currently operates in 868MHz band at a
data rate of 20Kbps in Europe, 914MHz band at 40kbps in USA, and the 2.4GHz ISM
bands Worldwide at a maximum data-rate of 250kbps
POWER SUPPLY
This section is meant for supplying Power to all the sections mentioned
above. It basically consists of a Transformer to step down the 230V ac to 18V ac followed by
diodes. Here diodes are used to rectify the ac to dc. After rectification the obtained rippled dc
is filtered using a capacitor Filter. A positive voltage regulator is used to regulate the obtained
dc voltage.
But here in this project two power supplies are used one is meant to supply operating
voltage for Microcontroller and the other is to supply control voltage for Relays.
H-BRIDGE:
H-bridge. Sometimes called a "full bridge" the H-bridge is so named because it has four
switching elements at the "corners" of the H and the motor forms the cross bar.
The key fact to note is that there are, in theory, four switching elements within the bridge.
These four elements are often called, high side left, high side right, low side right, and low
side left (when traversing in clockwise order).
DC Motor DC motors are configured in many types and sizes, including brush less, servo, and gear motor types. A motor consists of a rotor and a permanent magnetic field stator. The magnetic field is maintained using either permanent magnets or electromagnetic windings. DC motors are most commonly used in variable speed and torque.
6.SCHEMATIC DIAGRAM:
9
TRANSMITTER:
RECEIVER:
10
7.SCHEMATIC EXPLANATION:
Transmitter:1. Latch (74LS244)
Data pins:
Pins (9, 16) - P3.0
Pins (2, 13) - P3.1
Pin 4 - MAX 12 pin
Pin 18 - MAX 11 pin
Pin 11 - Zigbee 2 pin
Pin 12 - ZigBee 3 pin
Pin 20 – VCC
Pin 10 - GND
Control pins:
Pin 1- P3.6
Pin 19 - P3.7
2. MAX232:
Data pins:
Pin 14-DB9 connector 2 pin (to PC)
11
Pin 13-DB9 connector 3 pin (to PC)
3. Microcontroller:
Pin 40- VCC
Pin 20 –GND
Pin 18-XTAL1
Pin 19-XTAL2
Receiver:
1. ZigBee connection
Xbee 2-P3.0
Xbee 3-P3.1
2. Microcontroller:
Pin 40- VCC
Pin 20 –GND
Pin 18-XTAL1
Pin 19-XTAL2
3. H-bridge:
H-bridge connections (4 pins) –P1.0-P1.3
Power supply:In this system we are using 5V power supply for microcontroller at pin 40 of
Transmitter section as well as receiver section. Where as for ZigBee transceiver we are
providing a voltage of 3V to pin 1 all transceivers .The full description of the Power supply
section is given in this documentation in the following sections i.e. hardware components.
Latch: In this section all the pin connections of IC s and other devices are explained clearly.
Zigbee transceiver is used for transmitting data. So it get data from latch i.e. the DOUT (pin 2
of Zigbee) is connected to the pin 11 of latch 74LS244 and DIN (pin 3 of Zigbee) is
connected to the pin 12 of latch 74LS244. Pin 20 and pin 10 are used for VCC and GND.
PC:
12
Here Latch pins 18 and 4 are connected to MAX 232 pins 11 and 12 respectively. From
MAX 14 and 13 pins it is connected to 2 and 3 pins of DB9 connector respectively to get data
from PC.
Microcontroller: The RxD (pin 10) and TxD (pin 11) pins of microcontroller are connected to latch
through to (9, 16) and (2, 3) respectively.
Receiver:
Zigbee transceiver:Here Zigbee transceiver is used for receiving data from transmitter. To transfer data between
microcontroller and ZigBee we use two pins, one is transmission (TxD) and reception (RxD).
The DOUT (pin 2 of Zigbee) is connected to the pin P3.0 and DIN (pin 3 of Zigbee) is
connected to P3.0.
Power supply:In this system we are using 5V power supply for microcontroller at pin 40 of
Transmitter section as well as receiver section. Where as for ZigBee transceiver we are
proving a voltage of 3V to pin 1 all transceivers .The full description of the Power supply
section is given in this documentation in the following sections i.e. hardware components.
H-Bridge Connections to Micro controller:
We are using two H-bridges to control robot .One H-bridge inputs are connected to
the 1st and 2nd pins of the Micro controller. The other H-bridge inputs are connected to the 3rd
and 4th pins of the Micro controller.
ZIGBEE Technology:
ZIGBEE is a new wireless technology guided by the IEEE 802.15.4 Personal Area
Networks standard. It is primarily designed for the wide ranging automation applications and
to replace the existing non-standard technologies. It currently operates in the 868MHz band at
a data rate of 20Kbps in Europe, 914MHz band at 40Kbps in the USA, and the 2.4GHz ISM
bands Worldwide at a maximum data-rate of 250Kbps.
13
The ZIGBEE specification is a combination of HomeRF Lite and the 802.15.4
specification. The specification operates in the 2.4GHz (ISM) radio band - the same band as
802.11b standard, Bluetooth, microwaves and some other devices. It is capable of connecting
255 devices per network. The specification supports data transmission rates of up to 250
Kbps at a range of up to 30 meters. ZIGBEE's technology is slower than 802.11b (11 Mbps)
and Bluetooth (1 Mbps) but it consumes significantly less power.
802.15.4 (ZIGBEE) is a new standard uniquely designed for low rate wireless
personal area networks. It targets low data rate, low power consumption and low cost
wireless networking, and its goal is to provide a physical-layer and MAC-layer standard for
such networks.
Wireless networks provide advantages in deployment, cost, size and distributed
intelligence when compared with wired networks. This technology allows users to set up a
network quickly, and allows them to set up networks where it is impossible or inconvenient
to wire cables. Wireless networks are more cost-efficient than wired networks in general.
Bluetooth (802.15.1) was the first well-known wireless standard facing low data rate
applications. The effort of Bluetooth to cover more applications and provide quality of
service has led to its deviation from the design goal of simplicity, which makes it expensive
and inappropriate for some simple applications requiring low cost and low power
consumption. These are the kind of applications this new standard is focused on. It's relevant
to compare here Bluetooth and ZIGBEE, as they are sometimes seen as competitors, to show
their differences and to clarify for which applications suits each of them.
The data transfer capabilities are much higher in Bluetooth, which is capable of
transmitting audio, graphics and pictures over small networks, and also appropriate for file
transfers. ZIGBEE, on the other hand, is better suited for transmitting smaller packets over
large networks; mostly static networks with many, infrequently used devices, like home
automation, toys, remote controls, etc. While the performance of a Bluetooth network drops
when more than 8 devices are present, ZIGBEE networks can handle 65000+ devices.
Probably the main feature of ZIGBEE is its limited power requirement. ZIGBEE is
better for devices where the battery is rarely replaced, as it is designed to optimize slave
power requirements, and battery life can be up to 2 years with normal batteries. Bluetooth is a
14
cable replacement for items like phones, laptop computers and headsets. Bluetooth devices
expect regular charging and use a power model like a mobile phone.
ZIGBEE is also outstanding when facing timing critical, low power applications. The
join time for a new slave is typically 30ms, and the time needed by a slave changing from
sleeping to active, or accessing the channel is typically 15ms. Bluetooth devices need 3
seconds to either join a network or to change to active from sleeping state, though they are
much faster accessing the channel (around 2ms).
Need for ZIGBEE Technology:ZIGBEE is the only wireless standards-based technology that addresses the unique
needs of remote monitoring and control, sensory network applications. Sensors and controls
don’t need high bandwidth but they do need low latency and very low energy consumption
for long battery lives and for large device arrays.
There are a multitude of standards that address mid to high data rates for voice, PC
LANs, video, etc. However, up till now there hasn’t been a wireless network standard that
meets the unique needs of sensors and control devices. There are a multitude of proprietary
wireless systems manufactured today to solve a multitude of problems that also don’t require
high data rates but do require low cost and very low current drain.
This network has large number of nodes when compared to other technologies. It is
easy to deploy and configure i.e., if any new node enters into the network it automatically
senses and configure it. The Zigbee device is interoperable.
2.3 Features Standards-based wireless technology
Interoperability and worldwide usability
Low data-rates
Ultra low power consumption
Very small protocol stack
Support for small to excessively large networks
Simple design
Security
Reliability
2.4 Parameters
15
Operating frequency : 2.4GHz
Operating voltage : 3.3V
Transmitted power : 1mw
Range : 30m(urban area), 200m (LOS)
Data rate : 250Kbps
Operating temperature range : -40oC to +80oC
Receiver sensitivity : -104dbm
Frequency range : 2.4 – 2.4875 GHz.
2.5 Network Topologies
Fig 2.1 Network Topologies
There are three different network topologies that are supported by Zigbee, namely the
star, mesh and cluster tree or hybrid networks. Each has its own advantages and can be used
to advantage in different situations.
The star network is commonly used, having the advantage of simplicity. In the star
topology, the communication is established between devices and a single central controller,
called the PAN coordinator. The PAN coordinator is the primary controller of the PAN. All
devices operating on a network of either topology shall have unique 64 bit extended address,
16
which can be exchanged for a short address allocated by the PAN coordinator when the
device associates.
Mesh or peer-to-peer networks enable high degrees of reliability. The mesh topology
also has a PAN coordinator, but any device can communicate with any other device as long
as they are in range of one another. Mesh topology allows more complex network formations
to be implemented. Mesh networking allows for redundancy in node links, so that if one node
goes down, devices can find an alternative path to communicate with one another.
Cluster Tree network is essentially a combination of star and mesh topologies. Each
independent PAN will select a unique identifier. This PAN identifier allows communications
between devices within a network using short addresses and enables transmissions between
devices across independent networks.
Network Elements
There are three network elements:
PAN Coordinator (Personal Area Network Coordinator)
The central coordinator in a network is called PAN Coordinator.
The PAN Coordinator is the primary controller of the PAN.
Uses a specific 16-bit PAN ID.
It has self healing property.
FFD (Full Function Device)
This acts as a ZigBee Router.
Helps form the mesh and route data.
This performs other functions like sensing.
RFD (Reduced Function Device)
This cannot act as a router.
This is the end node of the network.
One RFD node cannot communicate directly with other RFD node.
2.6 Wireless technologies
17
Fig 2.2 Various Wireless Technologies
The above figure illustrates data rates and operating range of Zigbee in comparison with
other wireless technologies. The different technologies and standards mentioned above are
classified under two networks.
WPAN (Wireless Personal Area Network)
WLAN (Wireless local Area Network)
In WPAN we have two competing technologies Zigbee, Bluetooth. The data rate of
Zigbee is 250 kbps and that of Bluetooth is 1Mbps. Zigbee is focused on automation whereas
Bluetooth focuses on connectivity between laptops and PDA’s.
In WLAN we have other technologies like WI-FI, WIMAX and HiperLAN. The data
rates are high in WLAN which ranges from 1-54 Mbps. These technologies are costlier and
complex when compared Zigbee. The below table shows the difference between different
wireless technologies.
Table: 2.1 Comparisons of Various WLAN Technologies ZigBee 802.11
(Wi-Fi)Bluetooth UWB (Ultra
Wide Band)Wireless
USBIR
Wireless
Data Rate 20, 40, and 250 Kbits/s
11 & 54 Mbits/sec
1 Mbits/s 100-500 Mbits/s
62.5 Kbits/s
20-40 Kbits/s
18
Range 10-100 meters
50-100 meters
10 meters <10 meters 10 meters <10 meters (LOS)
Networking Topology
peer to peer, star, or mesh
Point to hub Ad-hoc, very small networks
Point to point Point to point
Point to point
Operating Frequency
2.4 GHz 2.4 & 5 GHz
2.4 GHz 3.1-10.6 GHz 2.4 GHz 800-900 nm
Complexity Low High High Medium Low Low
Power Consumption
Very low High Medium Low Low Low
Security 128 AES plus
application layer security
64 and 128 bit
encryption
Typical Applications
Industrial control
and monitoring, sensor networks, building
automation, home control
Wireless LAN
connectivity, broadband
Internet access
Wireless connectivity
between devices such as phones,
PDA, laptops, headsets
Streaming video, home entertainment applications
PC peripheral connection
s
Remote controls, PC, PDA, phone, laptop links
Application:
Building Automation
HVAC Control
Asset Tracking
Building Lighting
Industrial Control
19
Asset Management
Process Control
Environmental Monitor
Energy Management
Metering
Medical Sensing and Monitoring
Patient monitoring
Fitness monitoring
Consumer Electronics
o TVo VCRo DVD/CDo Remote Controlo Interactive Toys
BUILDING PC and Peripherals
Mouse Keyboard Joystick Commercial control
Home Security Lawn Irrigation Home Remote Control Home Remote monitor
8.HARDWARE DESIGN:Introduction
IN this chapter we are going to cover all parts of “wireless data transfer between
two or more PC’s” in detailed manner and their functions in brief. Here we are more
interested about the Microcontroller since it is the heart of the project. So the complete
architecture is explained and also significance of the Microcontroller.
Hardware components:
1. microcontroller
2. transceiver
3. power supply
4. DC motor
20
5. H-bridge
MICROCONTROLLER
Introduction:
A Micro controller consists of a powerful CPU tightly coupled with memory RAM,
ROM or EPROM), various I / O features such as Serial ports, Parallel Ports, Timer/Counters,
Interrupt Controller, Data Acquisition interfaces-Analog to Digital Converter (ADC), Digital
to Analog Converter (ADC), everything integrated onto a single Silicon Chip.
It does not mean that any micro controller should have all the above said features on
chip, Depending on the need and area of application for which it is designed, The ON-CHIP
features present in it may or may not include all the individual section said above.
Any microcomputer system requires memory to store a sequence of instructions
making up a program, parallel port or serial port for communicating with an external system,
timer / counter for control purposes like generating time delays, Baud rate for the serial port,
apart from the controlling unit called the Central Processing Unit.
Advantages of microcontrollers:
A system is developed with a microprocessor, the designer has to go for external
memory such as RAM, ROM or EPROM and peripherals and hence the size of the PCB will
be large enough to hold all the required peripherals. But, the micro controller has got all these
peripheral facilities on a single chip so development of a similar system with a micro
controller reduces PCB size and cost of the design.
One of the major differences between a micro controller and a microprocessor is that a
controller often deals with bits , not bytes as in the real world application, for example switch
contacts can only be open or close, indicators should be lit or dark and motors can be either
turned on or off and so forth.
INTRODUCTION TO ATMEL MICROCONTROLLERSERIES: 89C51 Family, TECHNOLOGY: CMOS
The major Features of 8-bit Micro controller ATMEL 89C51:
8 Bit CPU optimized for control applications
Extensive Boolean processing (Single - bit Logic) Capabilities.
On - Chip Flash Program Memory
On - Chip Data RAM
21
Bi-directional and Individually Addressable I/O Lines
Multiple 16-Bit Timer/Counters
Full Duplex UART
Multiple Source / Vector / Priority Interrupt Structure
On - Chip Oscillator and Clock circuitry.
On - Chip EEPROM
SPI Serial Bus Interface
Watch Dog Timer
8051 BLOCK DIAGRAM:
22
Fig. 6.2.1 Architecture of AT89C51
PIN CONFIGURATION:
23
Pin Diagram of AT89C51
Pin Description:
VCC Supply voltage.
GND Ground.
Port 0
24
Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink
eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance
inputs. Port 0 may also be configured to be the multiplexed low order address/data bus during
accesses to external program and data memory. In this mode P0 has internal pull-ups. Port 0
also receives the code bytes during Flash programming, and outputs the code bytes during
program verification. External pull-ups are required during program verification.
Port 1
Port 1 is an 8-bit bidirectional I/O port with internal pull-ups.The Port 1 output
buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled
high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are
externally being pulled low will source current (IIL) because of the internal pull-ups. Port 1
also receives the low-order address bytes during Flash programming and verification.
Port 2
Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output
buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled
high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are
externally being pulled low will source current (IIL) because of the internal pull-ups. Port 2
emits the high-order address byte during fetches from external program memory and during
accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this
application it uses strong internal pull-ups. When emitting 1s. During accesses to external
data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2
Special Function Register. Port 2 also receives the high-order address bits and some control
signals during Flash programming and verification.
Port 3
Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output
buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled
high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are
externally being pulled low will source current (IIL) because of the pull-ups. Port 3 also
serves the functions of various special features of the AT89C51 as listed below:
25
Alternate Functions of PORT3
Port 3 also receives some control signals for Flash programming and verification.
Port Loading and Interfacing
The output buffers of Ports 1, 2, and 3 can each drive 4 LS TTL inputs. These ports
on NMOS versions can be driven in a normal manner by a TTL or NMOS circuit. Both
NMOS and CMOS pins can be driven by open-collector and open-drain outputs, but note
that0-to-1 transitions will not be fast. In he NMOS device, if the pin is driven by an open-
collector output, a 0-to-1 transition will have to be driven by the relatively weak depletion
mode FET in the CMOS device, an input 0turns off pull-up pFET3, leaving only the very
weak pull-up pFET2 to drive the transition. Port 0 output buffers can each drive 8 LS TTL
inputs. They do, however, require external pull-ups to drive NMOS inputs, except when
being used as the ADDRESS/DATA bus for external memory.
RST
Reset input. A high on this pin for two machine cycles while the oscillator is running
resets the device.
ALE/PROG
Address Latch Enable output pulse for latching the low byte of the address during
accesses to external memory. This pin is also the program pulse input (PROG) during Flash
programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator
frequency, and may be used for external timing or clocking purposes. Note, however, that one
ALE pulse is skipped during each access to external Data Memory. If desired, ALE
26
operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is
active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high.
Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.
PSEN
Program Store Enable is the read strobe to external program memory. When the
AT89C51 is executing code from external program memory, PSEN is activated twice each
machine cycle, except that two PSEN activations are skipped during each access to external
data memory.
EA/VPP
External Access Enable. EA must be strapped to GND in order to enable the device to
fetch code from external program memory locations starting at 0000H up to FFFFH. Note,
however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should
be strapped to VCC for internal program executions. This pin also receives the 12-volt
programming enable voltage (VPP) during Flash programming, for parts that require 12-volt
VPP.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating
circuit.
XTAL2
Output from the inverting oscillator is amplifier.
Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier,
which can be configured for use as an on-chip oscillator, as shown in Figure 21. Either a
quartz crystal or ceramic resonator may be used. To drive the device from an external clock
source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Fig 6.2.3.
There are no requirements on the duty cycle of the external clock signal, since the input to the
internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum
voltage high and low time specifications must be observed.
27
Idle Mode
In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain
active. The mode is invoked by software. The content of the on-chip RAM and all the special
functions registers remain unchanged during this mode. The idle mode can be terminated by
any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated
by a hard ware reset, the device normally resumes program execution, from where it left off,
up to two machine cycles before the internal reset algorithm takes control. On-chip hardware
inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To
eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset,
the instruction following the one that invokes Idle should not be one that writes to a port pin
or to external memory.
Fig 6.2.3 External Clock Drive Configuration
Tab 6.2.2 Status of External Pins
Power down Mode
In the power down mode the oscillator is stopped, and the instruction that invokes
power down is the last instruction executed. The on-chip RAM and Special Function
Registers retain their values until the power down mode is terminated. The only exit from
28
power down is a hardware reset. Reset redefines the SFRs but does not change the on-chip
RAM. The reset should not be activated before VCC is restored to its normal operating level
and must be held active long enough to allow the oscillator to restart and stabilize.
Power on reset:
When power is turned on, the circuit holds the RST pin high for an amount of time
that depends on the capacitor value and the rate at which it charges.
To ensure a valid reset, the RST pin must be held high long enough to allow the
oscillator to start up plus two machine cycles. On power up, Vcc should rise within
approximately 10ms. The oscillator start-up time depends on the oscillator frequency. For a
10 MHz crystal, the start-up time is typically 1ms.With the given circuit, reducing Vcc
quickly to 0 causes the RST pin voltage to momentarily fall below 0V. How ever, this voltage
is internally l limited and will not harm the device.
Memory organization:
* Logical Separation of Program and Data Memory *
All Atmel Flash micro controllers have separate address spaces for program and
Data memory as shown in Fig 1.The logical separation of program and data memory
Allows the data memory to be accessed by 8 bit addresses. This can be more quickly
Stored and manipulated by an 8 bit CPU Nevertheless 16 Bit data memory addresses
Can also be generated through the DPTR register.
Program memory can only be read. There can be up to 64K bytes of directly
addressable program memory. The read strobe for external program memory is the Program
Store Enable Signal (PSEN) Data memory occupies a separate address space from program
memory. Up to 64K bytes of external memory can be directly addressed in the external data
memory space. The CPU generates read and write signals, RD and Wr, during external data
memory accesses. External program memory and external data memory can be combined by
applying the RD and PSEN signals to the inputs of AND gate and using the output of the
fate as the read strobe to the external program/data memory.
Program memory:
Fig 1.1 shows the map of the lower part of the program memory, after reset, the CPU
begins execution from location 0000h. As shown in Fig 1.1 each interrupt is assigned a fixed
location in program memory. The interrupt causes the CPU to jump to that location, where
29
it executes the service routine. External Interrupt 0 for example, is assigned to location
0003h. If external Interrupt 0 is used, its service routine must begin at location 0003h. If the I
interrupt in not used its service location is available as general-purpose program memory.
Fig.2: Program Memory.
0033h
Timer 2 002Bh
Serial Port 0023h
Timer 1 001Bh
External 8 Bytes
Interrupt 1 0013h
Timer 0 000Bh
External
Interrupt 0 0003h
Reset 0000h
The interrupt service locations are spaced at 8 byte intervals 0003h for External
interrupt 0, 000Bh for Timer 0, 0013h for External interrupt 1,001Bh for Timer1, and so on.
If an Interrupt service routine is short enough (as is often the case in control applications) it
can reside entirely within that 8-byte interval. Longer service routines can use a jump
instruction to skip over subsequent interrupt locations. If other interrupts are in use. The
lowest addresses of program memory can be either in the on-chip Flash or in an external
memory. To make this selection, strap the External Access (EA) pin to either Vcc or GND.
For example, in the AT89C51 with 4K bytes of on-chip Flash, if the EA pin is strapped to
Vcc, program fetches to addresses 0000h through 0FFFh are directed to internal Flash.
Program fetches to addresses 1000h through FFFFh are directed to external memory.
Data memory:
The Internal Data memory is dived into three blocks namely, Refer Fig (1.1.1)
The lower 128 Bytes of Internal RAM.
The Upper 128 Bytes of Internal RAM.
Special Function Register.
30
FFh Accessible Accessible Upper By Indirect By Direct 128 Addressing Addressing
80h only.79h
Accessible Special Function Register Lower By Direct 128 and Indirect (Ports, Status and Control Bits)
00h Addressing
Internal Data memory Addresses are always 1 byte wide, which implies an address
space of only 256 bytes. However, the addressing modes for internal RAM can in fact
accommodate 384 bytes. Direct addresses higher than 7Fh access one memory space, and
indirect addresses higher than 7Fh access a different Memory Space.
The lowest 32 bytes are grouped into 4 banks of 8 registers. Program instructions call
out these registers as R0 through R7. Two bits in the Program Status Word (PSW) Select,
which register bank, is in use. This architecture allows more efficient use of code space, since
register instructions are shorter than instructions that use direct addressing.
The next 16-bytes above the register banks form a block of bit addressable memory
space. The micro controller instruction set includes a wide selection of single - bit
instructions and this instruction can directly address the 128 bytes in this area. These bit
addresses are 00h through 7Fh. either direct or indirect addressing can access all of the bytes
in lower 128 bytes. Indirect addressing can only access the upper 128. The upper 128 bytes of
RAM are only in the devices with 256 bytes of RAM.
The Special Function Register includes Port latches, timers, peripheral controls etc.,
direct addressing can only access these register. In general, all Atmel micro controllers have
the same SFRs at the same addresses in SFR space as the AT89C51 and other compatible
micro controllers. However, upgrades to the AT89C51 have additional SFRs. Sixteen
addresses in SFR space are both byte and bit Addressable. The bit Addressable SFRs are
those whose address ends in 000B. The bit addresses in this area are 80h through FFh.
FFFFh FFFFh
External
31
External
FFh
EA = 0 EA = 1
External External 0000h
-0000- 00h
PSEN RD WR
Fig.1.1 89C51 MEMORY STRUCTURE
ADDRESSING MODES:
Direct addressing:
In direct addressing, the operand specified by an 8-bit address field in the instruction.
Only internal data RAM and SFR’s can be directly addressed.
Indirect addressing:
In Indirect addressing, the instruction specifies a register that contains the address of
the operand. Both internal and external RAM can indirectly address.
The address register for 8-bit addresses can be either the Stack Pointer or R0 or R1 of
the selected register Bank. The address register for 16-bit addresses can be only the 16-bit
data pointer register, DPTR.
Indexed addressing:
Program memory can only be accessed via indexed addressing this addressing mode
is intended for reading look-up tables in program memory. A 16 bit base register (Either
DPTR or the Program Counter) points to the base of the table, and the accumulator is set up
with the table entry number. Adding the Accumulator data to the base pointer forms the
address of the table entry in program memory.
Another type of indexed addressing is used in the“ case jump ” instructions. In this
case the destination address of a jump instruction is computed as the sum of the base pointer
and the Accumulator data.
32
Register instruction:
The register banks, which contains registers R0 through R7, can be accessed by
instructions whose opcodes carry a 3-bit register specification. Instructions that access the
registers this way make efficient use of code, since this mode eliminates an address byte.
When the instruction is executed, one of four banks is selected at execution time by the row
bank select bits in PSW.
Register - specific instruction:
Some Instructions are specifiec to a certain register. For example some instruction
always operates on the Accumulator, so no address byte is needed to point OT ir. Inthese
cases, the opcode itself points to the correct register. Instruction that regger to Accumulator
as A assemble as Accumulator - specific Opcodes.
PROGRAM STATUS WORD:
Program Status Word Register in Atmel Flash Micro controller:
CY AC F0 RS1 RS0 OV --- P
PSW 7 PSW 0
PSW 6 PSW 1
PSW 5 PSW 2
PSW 4 PSW 3
PSW0: Parity of Accumulator Set By Hardware To 1 if it contains an Odd number of
1s, otherwise it is reset to 0.
PSW1: User Definable Flag
PSW2: Overflow Flag Set By Arithmetic Operations
PSW3: Register Bank Select
PSW4: Register Bank Select
PSW5: General Purpose Flag.
PSW6: Auxiliary Carry Flag Receives Carry Out from
Bit 1 of Addition Operands
PSW7: Carry Flag Receives Carry Out From Bit 1 of ALU Operands.
33
The Program Status Word contains Status bits that reflect the current state of the
CPU. The PSW shown if Fig resides in SFR space. The PSW contains the Carry Bit, The
auxiliary Carry (For BCD Operations) the two - register bank select bits, the Overflow flag, a
Parity bit and two user Definable status Flags.
The Carry Bit, in addition to serving as a Carry bit in arithmetic operations also serves
the as the “Accumulator” for a number of Boolean Operations .The bits RS0 and RS1 select
one of the four register banks. A number of instructions register to these RAM locations as
R0 through R7. The status of the RS0 and RS1 bits at execution time determines which of the
four banks is selected.
The Parity bit reflect the Number of 1s in the Accumulator .P=1 if the Accumulator
contains an even number of 1s, and P=0 if the Accumulator contains an even number of 1s.
Thus, the number of 1s in the Accumulator plus P is always even. Two bits in the PSW are
uncommitted and can be used as general-purpose status flags.
Immediate constants:
The value of a constant can follow the opcode in program memory For example.
MOV A, #100 loads the Accumulator with the decimal number 100. The same number could
be specified in hex digit as 64h.
Oscillator and clock circuit:
XTAL1 and XTAL2 are the input and output respectively of an inverting amplifier
which is intended for use as a crystal oscillator in the pioerce configuration, in the frequency
range of 1.2 Mhz to 12 Mhz. XTAL2 also the input to the internal clock generator.
To drive the chip with an internal oscillator, one would ground XTAL1 and XTAL2.
Since the input to the clock generator is dividing by two flip flops there are no requirements
on the duty cycle of the external oscillator signal. However, minimum high and low times
must be observed.
The clock generator divides the oscillator frequency by 2 and provides a tow phase
clock signal to the chip. The phase 1 signal is active during the first half to each clock period
and the phase 2 signals are active during the second half of each clock period.
34
CPU Timing:
A machine cycle consists of 6 states. Each stare is divided into a phase / half, during
which the phase 1 clock is active and phase 2 half. Arithmetic and Logical operations take
place during phase1 and internal register - to register transfer take place during phase 2
Timers:The 8051 comes equipped with two timers, both of which may be controlled, set,
read, and configured individually. The 8051 timers have three general functions: 1) Keeping
time and/or calculating the amount of time between events, 2) Counting the events
themselves, or 3) Generating baud rates for the serial port.
The three timer uses are distinct so we will talk about each of them separately.
The first two uses will be discussed in this chapter while the use of timers for baud rate
generation will be discussed in the chapter relating to serial ports.
How does a timer count?
How does a timer count? The answer to this question is very simple: A timer always
counts up. It doesn’t matter whether the timer is being used as a timer, a counter, or a baud
rate generator: A timer is always incremented by the microcontroller.
Programming Tip: Some derivative chips actually allow the program to configure whether
the timers count up or down. However, since this option only exists on some derivatives it is
beyond the scope of this tutorial which is aimed at the standard 8051. It is only mentioned
here in the event that you absolutely need a timer to count backwards, you will know that you
may be able to find an 8051-compatible microcontroller that does it.
USING TIMERS TO MEASURE TIME
Obviously, one of the primary uses of timers is to measure time. We will discuss this
use of timers first and will subsequently discuss the use of timers to count events. When a
timer is used to measure time it is also called an "interval timer" since it is measuring the time
of the interval between two events.
How long does a timer take to count?
First, it’s worth mentioning that when a timer is in interval timer mode (as opposed to
event counter mode) and correctly configured, it will increment by 1 every machine cycle. As
you will recall from the previous chapter, a single machine cycle consists of 12 crystal pulses.
Thus a running timer will be incremented:
11,059,000 / 12 = 921,583
35
921,583 times per second. Unlike instructions--some of which require 1 machine cycle,
others 2, and others 4--the timers are consistent: They will always be incremented once per
machine cycle. Thus if a timer has counted from 0 to 50,000 you may calculate:
50,000 / 921,583 = .0542
.0542 seconds have passed. In plain English, about half of a tenth of a second, or one-
twentieth of a second.
Obviously it’s not very useful to know .0542 seconds have passed. If you want to
execute an event once per second you’d have to wait for the timer to count from 0 to 50,000
18.45 times. How can you wait "half of a time?" You can’t. So we come to another important
calculation.
Let’s say we want to know how many times the timer will be incremented in .05
seconds. We can do simple multiplication:
.05 * 921,583 = 46,079.15.
This tells us that it will take .05 seconds (1/20th of a second) to count from 0 to 46,079.
Actually, it will take it .049999837 seconds--so we’re off by .000000163 seconds--however,
that’s close enough for government work. Consider that if you were building a watch based
on the 8051 and made the above assumption your watch would only gain about one second
every 2 months. Again, I think that’s accurate enough for most applications--I wish my watch
only gained one second every two months.
Obviously, this is a little more useful. If you know it takes 1/20th of a second to count
from 0 to 46,079 and you want to execute some event every second you simply wait for the
timer to count from 0 to 46,079 twenty times; then you execute your event, reset the timers,
and wait for the timer to count up another 20 times. In this manner you will effectively
execute your event once per second, accurate to within thousandths of a second.
Thus, we now have a system with which to measure time. All we need to review is
how to control the timers and initialize them to provide us with the information we need.
Timer SFRs:
As mentioned before, the 8051 has two timers which each function essentially the
same way. One timer is TIMER0 and the other is TIMER1. The two timers share two SFRs
36
(TMOD and TCON) which control the timers, and each timer also has two SFRs dedicated
solely to itself (TH0/TL0 and TH1/TL1).
The TMOD SFR:
The TMOD SFR is used to control the mode of operation of both timers. Each bit of
the SFR gives the microcontroller specific information concerning how to run a timer. The
high four bits (bits 4 through 7) relate to Timer 1 whereas the low four bits (bits 0 through 3)
perform the exact same functions, but for timer 0.
The individual bits of TMOD have the following functions:
As you can see in the above chart, four bits (two for each timer) are used to specify a mode of
operation. The modes of operation are:
37
13-bit Time Mode (mode 0):
Timer mode "0" is a 13-bit timer. When the timer is in 13-bit mode, TLx will
count from 0 to 31. When TLx is incremented from 31, it will "reset" to 0 and increment
THx. Thus, effectively, only 13 bits of the two timer bytes are being used: bits 0-4 of TLx
and bits 0-7 of THx. This also means, in essence, the timer can only contain 8192 values. If
you set a 13-bit timer to 0, it will overflow back to zero 8192 machine cycles later.
16-bit Time Mode (mode 1):
Timer mode "1" is a 16-bit timer. This is a very commonly used mode. It
functions just like 13-bit mode except that all 16 bits are used. TLx is incremented from 0 to
255. When TLx is incremented from 255, it resets to 0 and causes THx to be incremented by
1. Since this is a full 16-bit timer, the timer may contain up to 65536 distinct values. If you
set a 16-bit timer to 0, it will overflow back to 0 after 65,536 machine cycles.
8-bit Time Mode (mode 2):
Timer mode "2" is an 8-bit auto-reload mode. When a timer is in mode 2, THx
holds the "reload value" and TLx is the timer itself. Thus, TLx starts counting up. When TLx
reaches 255 and is subsequently incremented, instead of resetting to 0 (as in the case of
modes 0 and 1), it will be reset to the value stored in THx.
The benefit of auto-reload mode is, if you want the timer to always have a
value from 200 to 255. If you use mode 0 or 1, you’d have to check in code to see if the timer
had overflowed and, if so, reset the timer to 200. This takes precious instructions of execution
time to check the value and/or to reload it. When you use mode 2 the microcontroller takes
care of this for you. Once you’ve configured a timer in mode 2 you don’t have to worry about
checking to see if the timer has overflowed nor do you have to worry about resetting the
value--the microcontroller hardware will do it all for you. The auto-reload mode is very
commonly used for establishing a baud rate for serial transmission and receiving.
38
Split Timer Mode (mode 3):
Timer mode "3" is a split-timer mode. When Timer 0 is placed in mode 3, it
essentially becomes two separate 8-bit timers. That is to say, Timer 0 is TL0 and Timer 1 is
TH0. Both timers count from 0 to 255 and overflow back to 0. All the bits that are related to
Timer 1 will now be tied to TH0.
While Timer 0 is in split mode, the real Timer 1 (i.e. TH1 and TL1) can be put
into modes 0, 1 or 2 normally--however, you may not start or stop the real timer 1 since the
bits that do that are now linked to TH0. The real timer 1, in this case, will be incremented
every machine cycle no matter what.
The only real use of split timer mode is if you need to have two separate
timers and, additionally, a baud rate generator. In such case you can use the real Timer 1 as a
baud rate generator and use TH0/TL0 as two separate timers.
The TCON SFR:
There is one more SFR that controls the two timers and provides valuable
information about them. The TCON SFR has the following structure:
As you may notice, we’ve only defined 4 of the 8 bits. That’s because the other 4 bits of the
SFR don’t have anything to do with timers--they have to do with Interrupts and they will be
discussed in the chapter that addresses interrupts.
Initializing a timer:
As you’ll recall, we first must decide what mode we want the timer to be in. In this
case we want a 16-bit timer that runs continuously; that is to say, it is not dependent on any
external pins. We must first initialize the TMOD SFR. Since we are working with timer 0 we
will be using the lowest 4 bits of TMOD. The first two bits, GATE0 and C/T0 are both 0
since we want the timer to be independent of the external pins. 16-bit mode is timer mode 1
39
so we must clear T0M1 and set T0M0. Effectively, the only bit we want to turn on is bit 0 of
TMOD. Thus to initialize the timer we execute the instruction: MOV TMOD,#01h
Timer 0 is now in 16-bit timer mode. However, the timer is not running. To start the
timer running we must set the TR0 bit, we can do that by executing the instruction: SETB
TR0
Upon executing these two instructions timer 0 will immediately begin counting, being
incremented once every machine cycle (every 12 crystal pulses).
Detecting Timer Overflow:
Often it is necessary to just know that the timer has reset to 0. That is to say, you are
not particularly interest in the value of the timer but rather you are interested in knowing
when the timer has overflowed back to 0. Whenever a timer overflows from it’s highest value
back to 0, the microcontroller automatically sets the TFx bit in the TCON register. This is
useful since rather than checking the exact value of the timer you can just check if the TFx bit
is set. If TF0 is set it means that timer 0 has overflowed; if TF1 is set it means that timer 1
has overflowed.
We can use this approach to cause the program to execute a fixed delay.
Timers as Event counters:
The 8051 provides us with a way to use the timers to count events. If we want to use
Timer 0 to count the number of events, set the C/T0 bit of the TMOD SFR. However, if we
set C/T0, timer 0 will monitor the P3.4 line. Instead of being incremented every machine
cycle, timer 0 will count events on the P3.4 line. So if we connect any sensor to P3.4 and let
the 8051 do the work. Then, when we want to know how many have occurred, we just read
the value of timer 0. The value of timer 0 will be the number of events that have occurred.
The 8051 counts one to zero transitions on the P3.4 line. This means that when there
is a raise on the P3.4 pin the 8051 will not count anything since this is a 0-1 transition.
However, when the sensor will fall back to a low ("0") state. This is a 1-0 transition and at
that instant the counter will be incremented by 1.
It is important to note that the 8051 checks the P3.4 line each instruction cycle (12
clock cycles). This means that if P3.4 is low, goes high, and goes back low in 6 clock cycles
it will probably not be detected by the 8051. This also means the 8051 event counter is only
capable of counting events that occur at a maximum of 1/24th the rate of the crystal
frequency. That is to say, if the crystal frequency is 12.000 MHz it can count a maximum of
500,000 events per second (12.000 MHz * 1/24 = 500,000). If the event being counted occurs
more than 500,000 times per second it will not be able to be accurately counted by the 8051.
40
SERIAL COMMUNICATIONTHEORY:
In order to connect micro controller to a modem or a pc to modem a serial port is
used. Serial is a very common protocol for device communication that is standard on almost
every PC. Most computers include two RS-232 based serial ports. Serial is also a common
communication protocol that is used by many devices for instrumentation; numerous GPIB-
compatible devices also come with an RS-232 port. Furthermore, serial communication can
be used for data acquisition in conjunction with a remote sampling device.
The concept of serial communication is simple. The serial port sends and receives
bytes of information one bit at a time. Although this is slower than parallel communication,
which allows the transmission of an entire byte at once, it is simpler and can be used over
longer distances. For example, the IEEE 488 specifications for parallel communication state
that the cabling between equipment can be no more than 20 meters total, with no more than 2
meters between any two devices. Serial, however, can extend as much as 1200 meters.
Typically, serial is used to transmit ASCII data. Communication is completed using 3
transmission lines: (1) Ground, (2) Transmit, and (3) Receive. Since serial is asynchronous,
the port is able to transmit data on one line while receiving data on another. Other lines are
available for handshaking, but are not required. The important serial characteristics are baud
rate, data bits, stop bits, and parity. For two ports to communicate, these parameters must
match.
Baud rate:
It is a speed measurement for communication. It indicates the number of bit transfers
per second. For example, 300 baud is 300 bits per second. When a clock cycle is referred it
means the baud rate. For example, if the protocol calls for a 4800 baud rate, then the clock is
running at 4800Hz. This means that the serial port is sampling the data line at 4800Hz.
Common baud rates for telephone lines are 14400, 28800, and 33600. Baud rates greater than
these are possible, but these rates reduce the distance by which devices can be separated.
These high baud rates are used for device communication where the devices are located
together, as is typically the case with GPIB devices.
Data bits:
41
Measurement of the actual data bits in a transmission. When the computer sends a
packet of information, the amount of actual data may not be a full 8 bits. Standard values for
the data packets are 5, 7, and 8 bits. Which setting chosen depends on what information
transferred? For example, standard ASCII has values from 0 to 127 (7 bits). Extended ASCII
uses 0 to 255 (8 bits). If the data being transferred is simple text (standard ASCII), then
sending 7 bits of data per packet is sufficient for communication. A packet refers to a single
byte transfer, including start/stop bits, data bits, and parity. Since the number of actual bits
depends on the protocol selected, the term packet is used to cover all instances.
Stop bits:
It is used to signal the end of communication for a single packet. Typical values are 1,
1.5, and 2 bits. Since the data is clocked across the lines and each device has its own clock, it
is possible for the two devices to become slightly out of sync. Therefore, the stop bits not
only indicate the end of transmission but also give the computers some room for error in the
clock speeds. The more bits that are used for stop bits, the greater the lenience in
synchronizing the different clocks, but the slower the data transmission rate.
Parity:
It is simple form of error checking that is used in serial communication. There are
four types of parity: even, odd, marked, and spaced. The option of using no parity is also
available. For even and odd parity, the serial port sets the parity bit (the last bit after the data
bits) to a value to ensure that the transmission has an even or odd number of logic high bits.
For example, if the data is 011, then for even parity, the parity bit is 0 to keep the number of
logic-high bits even. If the parity is odd, then the parity bit is 1, resulting in 3 logic-high bits.
Marked and spaced parity does not actually check the data bits, but simply sets the parity bit
high for marked parity or low for spaced parity. This allows the receiving device to know the
state of a bit to enable the device to determine if noise is corrupting the data or if the
transmitting and receiving device clocks are out of sync.
WHAT IS RS –232C
RS-232 (ANSI/EIA-232 Standard) is the serial connection found on IBM-compatible
PCs. It is used for many purposes, such as connecting a mouse, printer, or modem, as well as
industrial instrumentation. Because of improvements in line drivers and cables, applications
often increase the performance of RS-232 beyond the distance and speed listed in the
42
standard. RS-232 is limited to point-to-point connections between PC serial ports and
devices. RS-232 hardware can be used for serial communication up to distances of 50 feet .
DB-9 pin connector
1 2 3 4 5
6 7 8 9
(Out of computer and exposed end of cable)
Pin Functions:
Data: TxD on pin 3, RxD on pin 2
Handshake: RTS on pin 7, CTS on pin 8, DSR on pin 6,
CD on pin 1, DTR on pin 4
Common: Common pin 5(ground)
Other: RI on pin 9
The method used by RS-232 for communication allows for a simple connection of three lines:
Tx, Rx, and Ground. The three essential signals for 2 way RS-232
Communications are these:
TXD: carries data from DTE to the DCE.
RXD: carries data from DCE to the DTE
SG: signal ground
Connection Diagram:
SFRs Used for Serial Communication:
SCON:
43
TMOD:
T1:
BAUD RATE CALCULATION:
Internal timer stages are as follows
Divided by X box can be replaced with T1 timer so that by changing the value of timer we can obtain the required baud rate.
Let XClk = 11.0592 Mhz
Baud Rate = (XClk / 12 / 16 / 2 / X )
For attaining 9600 baud Rate
X can be calculated = 11.0592 x 106 / 12 / 16 / 2 / 9600 = 3
So set the 2’s Complement of 3 in Timer 1 so that we can achieve 9600 baud rates.
Note: Assuming 8-bit Auto reload mode and 8-bit variable baud rate modes.
FLOW CHART:
TX Loop:
44
RX Loop:
MAX 232Introduction:
45
Serial RS-232 (V.24) communication works with voltages (-15V ... -3V for high [sic])
and +3V ... +15V for low [sic]) which are not compatible with normal computer logic
voltages. On the other hand, classic TTL computer logic operates between 0V ... +5V
(roughly 0V ... +0.8V for low, +2V ... +5V for high). Modern low-power logic operates in the
range of 0V ... +3.3V or even lower.
o, the maximum RS-232 signal levels are far too high for computer logic electronics,
and the negative RS-232 voltage for high . Therefore, to receive serial data from an RS-232
interface the voltage has to be reduced, and the low and high voltage level inverted. In the
other direction (sending data from some logic over RS-232) the low logic voltage has to be
"bumped up", and a negative voltage has to be generated, too.
Logic Voltages
ll this can be done with conventional analog electronics, e.g. a particular power supply
and a couple of transistors or the once popular 1488 (transmitter) and 1489 (receiver) ICs.
However, since more than a decade it has become standard in amateur electronics to do the
necessary signal level conversion with an integrated circuit (IC) from the MAX232 family
(typically a MAX232A or some clone). In fact, it is hard to find some
The MAX232 & MAX232A
he MAX 232 translates RS232 voltages to TTL voltages. RS232 represent a binary 1
or HI anywhere between –3V to –12V, a zero logic or LOW, between 3V and 12V. TTL in
the other hand responds to 0 to 2.1V as logic zero and 2.8V to 5V as a HI. The MAX 232
provides voltage translation so the TTL PIC 16F84 can understand the messages sent to it
from the computer. A serial cable is also provided to connect the MAX232 to the PC and
jumper cables to connect the MAX232 to the micro controller.
he MAX232 from Maxim was the first IC which in one package contains the
necessary drivers (two) and receivers (also two), to adapt the RS-232 signal voltage levels to
TTL logic. It became popular, because it just needs one voltage (+5V) and generates the
necessary RS-232 voltage levels (approx. -10V and +10V) internally. This greatly simplified
the design of circuitry. Circuitry designers no longer need to design and build a power supply
46
with three voltages (e.g. -12V, +5V, and +12V), but could just provide one +5V power
supply, e.g. with the help of a simple 78x05 voltage converter.
MAX232 (A) DIP Package
DIP Package of MAX 232A
A Typical Application
The MAX232 (A) has two receivers (converts from RS-232 to TTL voltage levels) and two
drivers (converts from TTL logic to RS-232 voltage levels). This means only two of the RS-
232 signals can be converted in each direction. The old MC1488/1498 combo provided four
drivers and receivers.
Typically a pair of a driver/receiver of the MAX232 is used for
TX and RX and the second one for
CTS and RTS.
There are not enough drivers/receivers in the MAX232 to also connect the DTR, DSR, and
DCD signals. Usually these signals can be omitted when e.g. communicating with a PC's
serial interface. If the DTE really requires these signals either a second MAX232 is needed,
or some other IC from the MAX232 family can be used (if it can be found in consumer
electronic shops at all). An alternative for DTR/DSR is also given below.
Maxim's data sheet explains the MAX232 family in great detail, including the pin
configuration and how to connect such an IC to external circuitry. This information can be
used as-is in own design to get a working RS-232 interface. Maxim's data just misses one
47
critical piece of information: How exactly to connect the RS-232 signals to the IC. So here is
one possible example:
MAX232 to RS232 DB9 Connection as a DCE
MAX232 Pin Nbr. MAX232 Pin Name Signal Voltage DB9 Pin
7 T2out CTS RS-232 7
8 R2in RTS RS-232 8
9 R2out RTS TTL n/a
10 T2in CTS TTL n/a
11 T1in TX TTL n/a
12 R1out RX TTL n/a
13 R1in RX RS-232 2
14 T1out TX RS-232 3
15 GND GND 0 5
Connections between MAX 232 & RS 232
In addition one can directly wire DTR (DB9 pin 4) to DSR (DB9 pin 6) without going
through any circuitry. This gives automatic (brain dead) DSR acknowledgement of an
incoming DTR signal.
Sometimes pin 6 of the MAX232 is hard wired to DCD (DB9 pin 1). This is not
recommended. Pin 6 is the raw output of the voltage pump and inverter for the -10V voltage.
Drawing currents from the pin leads to a rapid breakdown of the voltage, and as a
consequence to a breakdown of the output voltage of the two RS-232 drivers. It is better to
use software which doesn't care about DCD, but does hardware-handshaking via CTS/RTS
only. The circuitry is completed by connecting five capacitors to the IC as it follows. The
MAX232 needs 1.0µF capacitors, the MAX232A needs 0.1µF capacitors. MAX232 clones
show similar differences. It is recommended to consult the corresponding data sheet. At least
16V capacitor types should be used. If electrolytic or tantalic capacitors are used, the polarity
has to be observed. The first pin as listed in the following table is always where the plus pole
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of the capacitor should be connected to. External Capacitors The 5V power supply is
connected to+5V: Pin 16 GND: Pin 15
MAX232(A) external Capacitors
Capacitor + Pin - Pin Remark
C1 1 3
C2 4 5
C3 2 16
C4 GND 6
This looks non-intuitive, but because pin 6 is
on -10V, GND gets the + connector, and not the
-
C5 16 GND
Drawbacks of MAX232: The MAX-232 chip receives data from the receiver, and converts it to the standard
RS-232 data format that can be read in by a serial port on a personal computer or
workstation.
For the RS-232 interface, a standard MAX232 chip is used for level conversion. Both
use the on chip USART and thus the same firmware.
CONNECTIONS IN MAX 232:
If you wanted to do a general RS-232 connection, you could take a bunch of long wires and
solder them directly to the electronic circuits of the equipment you are using, but this tends to
make a big mess and often those solder connections tend to break and other problems can
develop. To deal with these issues, and to make it easier to setup or take down equipment,
some standard connectors have been developed that is commonly found on most equipment
using the RS-232 standards.
These connectors come in two forms: A male and a female connector. The female connector
has holes that allow the pins on the male end to be inserted into the connector.
This is a female "DB-9" connector (properly known as DE9F):
49
Fig.6.5.1 Female Connector
The female DB-9 connector is typically used as the "plug" that goes into a typical PC. If you
see one of these on the back of your computer, it is likely not to be used for serial
communication, but rather for things like early VGA or CGA monitors (not SVGA) or for
some special control/joystick equipment.
And this is a male "DB-9" connector (properly known as DE9M):
Fig 6.5.2 Male Connector
This is the connector that you are more likely to see for serial communications on a "generic"
PC. Often you will see two of them side by side (for COM1 and COM2). Special equipment
that you might communicate with would have either connector, or even one of the DB-25
connectors listed below.
The wiring of RS-232 devices involves first identifying the actual pins that are being used.
Here is how a female DB-9 connector is numbered:
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If the numbers are hard to read, it starts at the top-right corner as "1", and goes left until the
end of the row and then starts again as pin 6 on the next row until you get to pin 9 on the
bottom-left pin. "Top" is defined as the row with 5 pins.
The male connector (like what you have on your PC) is simply this same order, but reversed
from right to left.
Here each pin is usually defined as:
9-pin 25-pin pin definition1 8 DCD (Data Carrier Detect)2 3 RX (Receive Data)3 2 TX (Transmit Data)4 20 DTR (Data Terminal Ready)5 7 GND (Signal Ground)6 6 DSR (Data Set Ready)7 4 RTS (Request To Send)8 5 CTS (Clear To Send))9 22 RI (Ring Indicator)
Tab 6.5.4 Pin Definition of Connectors
One thing to keep in mind when discussing these pins and their meaning is that they are very
closely tied together with modems and modem protocols. Often you don't have a modem
attached in the loop, but you still treat the equipment as if it were a modem on a theoretical
level.
BAUD RATES:
I'm going to go on a bit of a rant here. Baud and BPS (Bits Per Second) are usually not the
same thing, although they are often used interchangeable, particular in marketing literature.
Only originally they were the same. There are several ways to determine what the actual data
rate of a particular piece of equipment is, but in popular marketing literature, or even general
reference texts, they will almost always refer to "Baud Rate", even if they are referring to bits
per second.
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Language purists and engineers who know what they are talking about will go into a more
literal definition of Baud meaning the number of changes to the transmission media per
second in a modulated signal. If each transmission event contains more than one bit of
information, than Baud and BPS are not the same. E.g. if each event contains two bits (two
bits modulated in an event), then the BPS of such a transmission would be twice as large as
the Baud rate. This is not a theoretical case. Typical "high speed" modems use sophisticated
modulation on the telephone line, were the bit rate and Baud rate differ significantly on the
line. It is important to know this when you build measurement equipment, decoders
(demodulators), encoders (modulators), and all sorts of transmission equipment for a
particular protocol.
However, software developers typically like to ignore the difference of bit rate and baud rate,
because in their small world, a bit can either have the value true or false - an "event" (a bit)
always only has two possible states. They have no basic unit which can e.g. hold four
different states. In other words, on the software site the modulation has already been flattened
by the demodulator. If a modulation was used which can e.g. transmit 8 bits in an event, the
software developer sees them already as a series of 8 consecutive bits, each either true or
false. The demodulator took care of that. When it got an event it turned the single 8-bit event
into eight single-bit events. Software developers don't see the original single entity with 256
different states (voltages, phases). Since the modulation has been flattened they don't
experience the difference between Baud rate and bit rate any more. This is not the fault of the
people who defined a Baud or a BPS. It is just a (welcome) limitation of digital computer
hardware.
Baud is actually a shortened term named in honor of Émile Baudot, a French inventor of
early teleprinter machines that replaced the telegraph key using Morse code. Basically two
typewriters that could be connected to each other with some wires. He came up with some of
the first digital character encoding schemes, and the character codes were transmitted with a
serial data connection. Keep in mind this was being done largely before computers were
invented. Indeed, some of these early tele-printer devices were connected to the very first
computers like the ENIAC or UNIVAC, simply because they were relatively cheap and mass
produced at that point.
In order for serial data communication to happen, you need to agree on a clock signal, or
baud rate, in order to get everything to be both transmitted and received properly. This is
52
where the language purists get into it, because it is this clock signal that actually drives the
"baud rate". Let's start more at
Tele printers evolved, and eventually you have Western Union sending tele-printer
"cablegrams" all around the world. If you hear of a TELEX number, this is the relic of this
system, which is still in use at the present time, even with the internet. By rapidly glossing
over a whole bunch of interesting history, you end up with the United States Department of
Justice (DOJ) in a lawsuit with AT&T. Mind you this was an earlier anti-trust lawsuit prior to
the famous/infamous 1982 settlement. The reason this is important is because the DOJ
insisted that Western Union got all of the digital business (cable grams... and unfortunately
this got to be read as computer equipment as well), and AT&T got modulated frequencies, or
in other words, you could talk to your mother on Mother's Day on their equipment. When
computers were being built in the 1950s, people wanted some way to connect different pieces
of computer equipment together to "talk" to each other. This finally resulted in the RS-232
standard that we are discussing on this page.
While Western Union was permitted to carry digital traffic, often the connections weren't in
or near computer centers. At this time AT&T found a loophole in the anti-trust settlement that
could help get them into the business of being a "carrier" of computer data. They were also
offering to transmit computer data at rates considerably cheaper than Western Union was
going to charge. Hence, the modem was born.
Interrupts:As the name implies, an interrupt is some event which interrupts normal program
execution. As stated earlier, program flow is always sequential, being altered only by those
instructions which expressly cause program flow to deviate in some way. However, interrupts
give us a mechanism to "put on hold" the normal program flow, execute a subroutine, and
then resume normal program flow as if we had never left it. This subroutine, called an
interrupt handler, is only executed when a certain event (interrupt) occurs. The event may be
one of the timers "overflowing," receiving a character via the serial port, transmitting a
character via the serial port, or one of two "external events." The 8051 may be configured so
that when any of these events occur the main program is temporarily suspended and control
passed to a special section of code which presumably would execute some function related to
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the event that occurred. Once complete, control would be returned to the original program.
The main program never even knows it was interrupted.
The ability to interrupt normal program execution when certain events occur makes it
much easier and much more efficient to handle certain conditions. If it were not for interrupts
we would have to manually check in our main program whether the timers had overflows,
whether we had received another character via the serial port, or if some external event had
occurred. Besides making the main program ugly and hard to read, such a situation would
make our program inefficient since we’d be burning precious "instruction cycles" checking
for events that usually don’t happen.
We can configure the 8051 so that any of the following events will cause an interrupt:
• Timer 0 Overflow.
• Timer 1 Overflow.
• Reception/Transmission of Serial Character.
• External Event 0.
• External Event 1.
bviously we need to be able to distinguish between various interrupts and executing
different code depending on what interrupt was triggered. This is accomplished by jumping to
a fixed address when a given interrupt occurs as shown below.
By consulting the above chart we see that whenever Timer 0 overflows (i.e., the TF0 bit is
set), the main program will be temporarily suspended and control will jump to 000BH. It is
assumed that we have code at address 000BH that handles the situation of Timer 0
overflowing.
Setting up Interrupts:By default at power up, all interrupts are disabled. This means that even if, for
example, the TF0 bit is set, the 8051 will not execute the interrupt. Your program must
54
specifically tell the 8051 that it wishes to enable interrupts and specifically which interrupts it
wishes to enable.
Your program may enable and disable interrupts by modifying the IE SFR (A8h):
As you can see, each of the 8051’s interrupts has its own bit in the IE SFR. You enable a
given interrupt by setting the corresponding bit.
However, before enabling any interrupt, you must set bit 7 of IE. Bit 7, the Global
Interrupt Enable/Disable, enables or disables all interrupts simultaneously. That is to say, if
bit 7 is cleared then no interrupts will occur, even if all the other bits of IE are set. Setting bit
7 will enable all the interrupts that have been selected by setting other bits in IE. This is
useful in program execution if you have time-critical code that needs to execute. In this case,
you may need the code to execute from start to finish without any interrupt getting in the
way. To accomplish this you can simply clear bit 7 of IE (CLR EA) and then set it after your
time-critical code is done.
Interrupt priorities:The 8051 automatically evaluates whether an interrupt should occur
after every instruction. When checking for interrupt conditions, it checks them in the following order:
• External 0 Interrupt • Timer 0 Interrupt • External 1 Interrupt • Timer 1 Interrupt • Serial Interrupt
This means that if a Serial Interrupt occurs at the exact same instant that an External 0 Interrupt occurs, the External 0 Interrupt will be executed first and the Serial Interrupt will be executed once the External 0 Interrupt has completed.
55
The 8051 offers two levels of interrupt priority: high and low. By using interrupt
priorities you may assign higher priority to certain interrupt conditions. Interrupt priorities are
controlled by the IP SFR (B8h). The IP SFR has the following format:
When considering interrupt priorities, the following rules apply:
Nothing can interrupt a high-priority interrupt--not even another high priority
interrupt.
A high-priority interrupt may interrupt a low-priority interrupt.
A low-priority interrupt may only occur if no other interrupt is l ready executing.
If two interrupts occur at the same time, the interrupt with higher priority will execute
first. If both interrupts are of the same priority the interrupt which is serviced first by
polling sequence will be executed first.
When an interrupt is triggered, the following actions are taken automatically by the
microcontroller:
The current Program Counter is saved on the stack, low-byte first.
Interrupts of the same and lower priority are blocked.
In the case of Timer and External interrupts, the corresponding interrupt flag is
cleared.
Program execution transfers to the corresponding interrupt handler vector
address.
The Interrupt Handler Routine executes.
Take special note of the third step: If the interrupt being handled is a Timer or
External interrupt, the microcontroller automatically clears the interrupt flag before passing
control to your interrupt handler routine. This means it is not necessary that you clear the bit
in your code.
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DC GEARED MOTOR:
High efficiency, high quality low cost DC motor with gearbox for robotics applications. Very easy to use and available in standard size. Nut and threads on shaft to easily connect and internal threaded shaft for easily connecting it to wheel.Features
45 RPM 12V DC motors with Gearbox 5kgcm torque 3000RPM base motor 6mm shaft diameter with internal hole 125gm weight Same size motor available in various rpm No-load current = 60 mA(Max), Load current = 300 mA(Max)
MOTOR DRIVER
L293D:
The L293 is an integrated circuit motor driver that can be used for simultaneous, bi-
directional control of two small motors. Small means small. The L293 is limited to 600 mA,
but in reality can only handle much small currents unless you have done some serious heat
sinking to keep the case temperature down. Unsure about whether the L293 will work with
your motor? Hook up the circuit and run your motor while keeping your finger on the chip. If
57
it gets too hot to touch, you can't use it with your motor. (Note to ME2011 students: The
L293 should be OK for your small motor but is not OK for your gear motor.)
The L293 comes in a standard 16-pin, dual-in line integrated circuit package. There is an
L293 and an L293D part number. Pick the "D" version because it has built in flyback diodes
to minimize inductive voltage spikes.
The pinout for the L293 in the 16-pin package is shown below in top view. Pin 1 is at the top
left when the notch in the package faces up. Note that the names for pin functions may be
slightly different than what is shown in the following diagrams.
The following schematic shows how to connect the L293 to your motor and the Stamp. Each
motor takes 3 Stamp pins. If you are only using one motor, leave pins 9, 10, 11, 12, 13, 14,
and 15 empty.
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Assume you have only one motor connected with the enable tied to Stamp Pin 0, and the two
direction controls tied to Stamp Pins 1 and 2.
Here is a table describing the control pin functions.
ENABLE DIRA DIRB Function
H H L Turn right
H L H Turn left
H L/H L/H Fast stop
L either either Slow stop
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And here is a short sample program that exercises the L293.
H-Bridge:
Fig: shows the H-Bridge operation. The H-Bridge consists of a four PNP transistors
such as Q1, Q2, Q3 and Q4. These transistors are arranged in a way that a DC motor M can
rotate. A and B are represented as two inputs for operating a motor through the transistors.
For the circuit operation, we are providing +12V DC as a VCC. The operation will be
explained as follows:
The inputs A and B can be applied as a either logic ‘0’ or logic ‘1’ ie., may be either
5V DC voltage or Ground. If the input A =logic ‘0’ and B=logic’1’ then transistors Q1 and
Q4 will be ‘ON’ state and Q2 and Q3 will be ‘OFF’ state. The current flows from Q1 to Q4
so that the motor M can rotate in clockwise direction.
If the input A =logic ‘1’ and B=logic’0’ then transistors Q1 and Q4 will be ‘OFF’
state and Q2 and Q3 will be ‘ON’ state. The current flows from Q1 to Q4 so that the motor
M can rotate in Anti-clockwise direction.
If the input A =logic ‘1’ and B=logic’1’ then transistors Q1 and Q4 will be ‘OFF’
state and Q2 and Q3 will be ‘OFF’ state. No current flows from in the circuit. The circuit
will be in hold condition. The motor will not rotate any direction. So, there is no wastage of
power will occur. Otherwise, if both inputs are low that is all transistors are come under
working and more current will flows in the circuit. But the motor will be at hold condition.
More power is wasted.
PC:
60
The PC is generally used as the means of storing the gathered or acquired information at
the backend. The PC in some cases is also used as give the inputs to an Embedded System
through Serial Communication. The Serial Communication between the PC and our
Embedded System is done with the help of a Driver.
There is a need to use this Line Driver between a PC and
our Embedded System in order to match the Logic Levels of both. The Logic levels of
PC of Serial Port are RS 232 i.e. -3 to -25 for Logic 1 and +3 to +25 for Logic 0. And
the Logic Levels of our Embedded System with Microcontroller AT 89C51 are 0.0 to
0.8 for Logic 0 and 2.0 to 5.0 for Logic 1. Hence the PC is interfaced to
microcontroller 89C51 through Serial Interface Driver -MAX 232.
ZIGBEE TRANSCEIVER:
Pin Diagram
Fig: 6.1 Pin diagram of X-Bee Transceiver
61
Zigbee modules feature a UART interface, which allows any microcontroller or
microprocessor to immediately use the services of the Zigbee protocol. All a Zigbee hardware
designer has to do in this ase is ensure that the host’s serial port logic levels are compatible
with the XBee’s 2.8- to 3.4-V logic levels. The logic level conversion can be performed using
either a standard RS-232 IC or logic level translators such as the 74LVTH125 when the host
is directly connected to the XBee UART. The below table gives the pin description of
transceiver.
Table: 6.1 Pin Description of X-Bee Transceiver
Pin Name Direction Description
1 Vcc - Power Supply2 DOUT Output UART Data Out3 DIN/CONFIG Input UART Data In4 DO8 Output Digital Output 85 RESET Input Module Reset6 PWM0/RSSI Output PWM Output 0/RX Signal Strength Indicator7 PWM1 Output PWM Output 18 [reserved] - Do not connect9 DDR/SLEEP_RQ/DI8 Input Pin Sleep Control Line or Digital Input 810 GND - Ground11 AD4/DIO4 Either Analog Input 4 or Digital I/O 412 CTS/DIO7 Either Clear-to-Send Flow Control or Digital I/O 713 ON/SLEEP Output Module Status Indicator14 VREF Input Voltage Reference for A/D Inputs15 Associate/AD5/DIO5 Either Associated Indicator, Analog Input 5 or Digital
I/O 5
16 RTS/AD6/DIO6 Either Request-to-Send Flow Control, Analog Input 6 or Digital I/O 6
17 AD3/DIO3 Either Analog Input 3 or Digital I/O 318 AD2/DIO2 Either Analog Input 2 or Digital I/O 219 AD1/DIO1 Either Analog Input 1 or Digital I/O 120 AD0/DIO0 Either Analog Input 0 or Digital I/O 0
Design Notes: Minimum connections: VCC, GND, DOUT & DIN
62
Minimum connections for updating firmware: VCC, GND, DIN, DOUT, RTS and
DTR
Signal Direction is specified with respect to the module
Module includes a 50k pull-up resistor attached to RESET
Several of the input pull-ups can be configured using the PR command
Unused pins should be left disconnected
Features
Performance:
Table: 6.2 Performance characteristics
Parameters Value
Indoor/Urban Range 30m
Outdoor RF (LOS) 100m
Transmit Power Output 1mW (0dBm)
RF Data Rate 250,000bps
Serial Interface Data Rate 1200-115200bps
Receiver Sensitivity -92dBm
Power Requirements:
Table: 6.3 Power Requirement characteristics
Parameters Value
Supply Voltage 2.8 - 3.4V
Transmit Current 45mA
Receive Current 50mA
General:
Table: 6.4 General characteristics
63
Parameters Value
Operating Frequency ISM 2.4GHz
Dimensions 2.468 x 2.761
Operating Temperature -40o to 85o C
Antenna Options Integrated Chip Antenna
Networking and Security:
Table: 6.5 Networking and Security characteristics
Parameters Value
Supported Network Topologies Point-to-point, Point-to-multipoint, Peer-to-peer
Number of Channels 16 Direct Sequence Channels
Addressing Options PAN ID, Channel and Addresses
6.3 System Data Flow Diagram:
Fig: 6.2 Data Flow Diagram
The X-Bee RF Modules interface to a host device through a logic-level asynchronous
Serial port. Through its serial port, the module can communicate with any logic and voltage
Compatible UART; or through a level translator to any serial device.
Data is presented to the X-Bee module through its DIN pin, and it must be in the
asynchronous serial format, which consists of a start bit, 8 data bits, and a stop bit. Because
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the input data goes directly into the input of a UART within the X-Bee module, no bit
inversions are necessary within the asynchronous serial data stream. All of the required
timing and parity checking is automatically taken care of by the X-Bee’s UART.
Just in case you are producing data faster than the X-Bee can process and transmit it,
both X-Bee modules incorporate a clear-to-send (CTS) function to throttle the data being
presented to the X-Bee module’s DIN pin. You can eliminate the need for the CTS signal by
sending small data packets at slower data rates.
If the microcontroller wants to send data to transceiver, it will send RTS (Request to
Send) signal. If the transceiver is idle it sends CTS (Clear to Send) signal. The RTS and CTS
signals are active low. When microcontroller receives CTS command it will send data to the
transceiver through DIN pin. The transceiver will send the data to microcontroller through
DOUT pin. The communication between transceiver and the microcontroller at the
transmitter and receiver is similar. The communication between transmitter and receiver is
through RF communication.
6.4 Serial Data
Fig: 6.3 Serial Data Sequence
For example:
UART data packet 0x1F (decimal number is 31) as transmitted through the RF
module.
Data enters the module UART through the DI pin (pin 3) as an asynchronous serial
signal. The signal should idle high when no data is being transmitted. Each data byte consists
65
of a start bit (low), 8 data bits (least significant bit first) and a stop bit (high). The following
figure illustrates the serial bit pattern of data passing through the module.
The module UART performs tasks, such as timing and parity checking, that are
needed for data communications. Serial communications depend on the two UARTs to be
configured with compatible settings (baud rate, parity, start bits, stop bits, data bits).
X-Bee RF Modules operate in Transparent Mode. When operating in this mode, the
modules act as a serial line replacement - all UART data received through the DI pin is
queued up for RF transmission. When RF data is received, the data is sent out the DO pin.
Serial-to-RF Packetization
Data is buffered in the DI buffer until one of the following causes the data to be
packetized and transmitted:
No serial characters are received for the amount of time determined by the RO
(Packetization Timeout) parameter. If RO = 0, packetization begins when a character
is received.
The maximum number of characters that will fit in an RF packet (100) is received.
The Command Mode Sequence (GT + CC + GT) is received. Any character buffered
in the DI buffer before the sequence is transmitted.
If the module cannot immediately transmit (for instance, if it is already receiving RF
data), the serial data is stored in the DI Buffer. The data is packetized and sent at any RO
timeout or when 100 bytes (maximum packet size) are received.
If the DI buffer becomes full, hardware or software flow control must be implemented in
order to prevent overflow (loss of data between the host and module).
6.5 Internal Data Flow
66
Fig: 6.4 Internal Data Flow Diagram
DI (Data In) Buffer:
When serial data enters the RF module through the DI pin (pin 3), the data is stored in
the DI Buffer until it can be processed.
Hardware Flow Control (CTS):
When the DI buffer is 17 bytes away from being full; by default, the module de-
asserts CTS (high) to signal to the host device to stop sending data [refer to D7 (DIO7
Configuration) parameter]. CTS are re-asserted after the DI Buffer has 34 bytes of memory
available.
How to eliminate the need for flow control:
Send messages that are smaller than the DI buffer size.
Interface at a lower baud rate [BD (Interface Data Rate) parameter] than the
throughput data rate.
Case in which the DI Buffer may become full and possibly overflow:
If the module is receiving a continuous stream of RF data, any serial data that arrives
on the DI pin is placed in the DI Buffer. The data in the DI buffer will be transmitted over-
the-air when the module is no longer receiving RF data in the network.
DO (Data Out) Buffer:
67
When RF data is received, the data enters the DO buffer and is sent out the serial port
to a host device. Once the DO Buffer reaches capacity, any additional incoming RF data is
lost.
Hardware Flow Control (RTS):
If RTS is enabled for flow control (D6 (DIO6 Configuration) Parameter = 1), data
will not be sent out the DO Buffer as long as RTS (pin 16) is de-asserted.
Two cases in which the DO Buffer may become full and possibly overflow:
If the RF data rate is set higher than the interface data rate of the module, the module
will receive data from the transmitting module faster than it can send the data to the
host.
If the host does not allow the module to transmit data out from the DO buffer because
of being held off by hardware or software flow control.
6.6 I/O Data Format
I/O data begins with a header. The first byte of the header defines the number of
samples forthcoming. A sample is comprised of input data and the inputs can contain either
DIO or ADC. The last 2 bytes of the header (Channel Indicator) define which inputs are
active. Each bit represents either a DIO line or ADC channel.
Fig: 6.5 Header of I/O Data Format
Sample data follows the header and the channel indicator frame is used to determine
how to read the sample data. If any of the DIO lines are enabled, the first 2 bytes are the DIO
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data and the ADC data follows. ADC channel data is stored as an unsigned 10-bit value right-
justified on a 16-bit boundary.
Sample Data
Fig: 6.6 Sample Data of I/O Data Format
6.7 Networks:
The following IEEE 802.15.4 network types are supported by the Zigbee RF modules:
• NonBeacon
• NonBeacon (w/ Coordinator)
The following terms will be used to explicate the network operations:
Table 6.6: Terms and definitions:
Term Definition
PAN Personal Area Network - A data communication network that
includes one or more End Devices and optionally a Coordinator.
Coordinator A Full-function device (FFD) that provides network synchronization
by polling nodes [NonBeacon (w/ Coordinator) networks only]
End Device When in the same network as a Coordinator - RF modules that rely
on a Coordinator for synchronization and can be put into states of
sleep for low-power applications.
Association The establishment of membership between End Devices and a
Coordinator. Association is only applicable in NonBeacon
(w/Coordinator) networks.
6.7.1NonBeacon:
By default, XBee/XBee-PRO RF Modules are configured to support NonBeacon
communications. NonBeacon systems operate within a Peer-to-Peer network topology and
therefore are not depen-dent upon Master/Slave relationships. This means that modules
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remain synchronized without use of master/server configurations and each module in the
network shares both roles of master and slave. MaxStream's peer-to-peer architecture features
fast synchronization times and fast cold start times. This default configuration accommodates
a wide range of RF data applications.
A peer-to-peer network can be established by configuring each module to operate as
an End Device (CE = 0), disabling End Device Association on all modules (A1 = 0) and
setting ID and CH parameters to be identical across the network.
Figure 6.7: NonBeacon Peer-to-Peer Architecture
6.7.2 NonBeacon (w/ Coordinator):
A device is configured as a Coordinator by setting the CE (Coordinator Enable)
parameter to “1”. Coordinator power-up is governed by the A2 (Coordinator Association)
parameter.
In a NonBeacon (w/ Coordinator) system, the Coordinator can be configured to use
direct or indi-rect transmissions. If the SP (Cyclic Sleep Period) parameter is set to “0”, the
Coordinator will send data immediately. Otherwise, the SP parameter determines the length
of time the Coordinator will retain the data before discarding it. Generally, SP (Cyclic Sleep
Period) and ST (Time before Sleep) parameters should be set to match the SP and ST settings
of the End Devices.
6.7.3 Association:
Association is the establishment of membership between End Devices and a
Coordinator and is only applicable in NonBeacon (w/ Coordinator) networks. The
establishment of membership is useful in scenarios that require a central unit (Coordinator) to
relay messages to or gather data from several remote units (End Devices), assign channels or
assign PAN IDs.
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An RF data network that consists of one Coordinator and one or more End Devices
forms a PAN (Personal Area Network). Each device in a PAN has a PAN Identifier [ID
(PAN ID) parameter]. PAN IDs must be unique to prevent miscommunication between
PANs. The Coordinator PAN ID is set using the ID (PAN ID) and A2 (Coordinator
Association) commands.
An End Device can associate to a Coordinator without knowing the address, PAN ID
or channel of the Coordinator. The A1 (End Device Association) parameter bit fields
determine the flexibility of an End Device during association. The A1 parameter can be used
for an End Device to dynamically set its destination address, PAN ID and/or channel.
Coordinator / End Device Setup and Operation
To configure a module to operate as a Coordinator, set the CE (Coordinator Enable)
parameter to ‘1’. Set the CE parameter of End Devices to ‘0’ (default). Coordinator and End
Devices should con-tain matching firmware versions.
NonBeacon (w/ Coordinator) Systems
In a NonBeacon (w/ Coordinator) system, the Coordinator can be configured to use
direct or indirect transmissions. If the SP (Cyclic Sleep Period) parameter is set to ‘0’, the
Coordinator will send data immediately. Otherwise, the SP parameter determines the length
of time the Coordinator will retain the data before discarding it. Generally, SP (Cyclic Sleep
Period) and ST (Time before Sleep) parameters should be set to match the SP and ST settings
of the End Devices.
Coordinator Power-up
Coordinator power-up is governed by the A2 (Coordinator Association) command.
On power-up, the Coordinator undergoes the following sequence of events:
1. Check A2 parameter- Reassign_PANID Flag:
Set (bit 0 = 1) - The Coordinator issues an Active Scan. The Active Scan selects one channel
and transmits a Beacon Request command to the broadcast address (0xFFFF) and broadcast
PAN ID (0xFFFF). It then listens on that channel for beacons from any Coordinator operating
on that channel. The listen time on each channel is determined by the SD (Scan Duration)
parameter value.
Once the time expires on that channel, the Active Scan selects another channel and
again transmits the BeaconRequest as before. This process continues until all channels have
been scanned, or until 5 PANs have been discovered. When the Active Scan is complete, the
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results include a list of PAN IDs and Channels that are being used by other PANs. This list is
used to assign an unique PAN ID to the new Coordinator. The ID parameter will be retained
if it is not found in the Active Scan results. Otherwise, the ID (PAN ID) parameter setting
will be updated to a PAN ID that was not detected.
Not Set (bit 0 = 0) - The Coordinator retains its ID setting. No Active Scan is performed. For
example: If the PAN ID of a Coordinator is known, but the operating channel is not; the A1
command on the End Device should be set to enable the ‘Auto_Associate’ and ‘Reassign
Channel’ bits. Additionally, the ID parameter should be set to match the PAN ID of the
associated Coordinator.
2. Check A2 parameter - Reassign Channel Flag (bit 1)
Set (bit 1 = 1) - The Coordinator issues an Energy Scan. The Energy Scan selects one
channel and scans for energy on that channel. The duration of the scan is specified by the SD
(Scan Duration) parameter. Once the scan is completed on a channel, the Energy Scan selects
the next channel and begins a new scan on that channel. This process continues until all
channels have been scanned.
When the Energy Scan is complete, the results include the maximal energy values
detected on each channel. This list is used to determine a channel where the least energy was
detected. If an Active Scan was performed (Reassign_PANID Flag set), the channels used by
the detected PANs are eliminated as possible channels. Thus, the results of the Energy Scan
and the Active Scan (if performed) are used to find the best channel (channel with the least
energy that is not used by any detected PAN). Once the best channel has been selected, the
CH (Channel) param-eter value is updated to that channel.
Not Set (bit 1 = 0) - The Coordinator retains its CH setting. An Energy Scan is not
performed.
3. Start Coordinator
The Coordinator starts on the specified channel (CH parameter) and PAN ID (ID
parameter). Note, these may be selected in steps 1 and/or 2 above. The Coordinator will only
allow End Devices to associate to it if the A2 parameter “Allow Association” flag is set.
Once the Coordinator has successfully started, the Associate LED will blink 1 time per
second. (The LED is solid if the Coordinator has not started.)
4. Coordinator Modifications
Once a Coordinator has started:
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Modifying the A2 (Reassign_Channel or Reassign_PANID bits), ID, CH or MY
parameters will cause the Coordinator’s MAC to reset (The Coordinator RF module
(including volatile RAM) is not reset). Changing the A2 Allow Association bit will not reset
the Coordinator’s MAC. In a non-beaconing system, End Devices that associated to the
Coordinator prior to a MAC reset will have knowledge of the new settings on the
Coordinator. Thus, if the Coordinator were to change its ID, CH or MY settings, the End
Devices would no longer be able to communicate with the non-beacon Coordinator. Once a
Coordinator has started, the ID, CH, MY or A2 (Reassign_Channel or Reassign_PANID bits)
should not be changed.
End Device Power-up
End Device power-up is governed by the A1 (End Device Association) command. On
power-up, the End Device undergoes the following sequence of events:
1. Check A1 parameter - AutoAssociate Bit
Set (bit 2 = 1) - End Device will attempt to associate to a Coordinator.
Not Set (bit 2 = 0) - End Device will not attempt to associate to a Coordinator. The End
Device will operate as specified by its ID, CH and MY parameters. Association is considered
complete and the Associate LED will blink quickly (5 times per second). When the
AutoAssociate bit is not set, the remaining steps (2-3) do not apply.
2. Discover Coordinator (if Auto-Associate Bit Set)
The End Device issues an Active Scan. The Active Scan selects one channel and
transmits a Beacon Request command to the broadcast address (0xFFFF) and broadcast PAN
ID (0xFFFF). It then listens on that channel for beacons from any Coordinator operating on
that channel. The listen time on each channel is determined by the SD parameter.
Once the time expires on that channel, the Active Scan selects another channel and
again transmits the Beacon Request command as before. This process continues until all
channels have been scanned, or until 5 PANs have been discovered. When the Active Scan is
complete, the results include a list of PAN IDs and Channels that are being used by detected
PANs.
The End Device selects a Coordinator to associate with according to the A1 parameter
“Reassign_PANID” and “Reassign_Channel” flags:
Reassign_PANID Bit Set (bit 0 = 1)- End Device can associate with a PAN with any ID
value.
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Reassign_PANID Bit Not Set (bit 0 = 0) - End Device will only associate with a PAN
whose ID setting matches the ID setting of the End Device.
Reassign_Channel Bit Set (bit 1 = 1) - End Device can associate with a PAN with any CH
value.
Reassign_Channel Bit Not Set (bit 1 = 0)- End Device will only associate with a PAN
whose CH setting matches the CH setting of the End Device.
After applying these filters to the discovered Coordinators, if multiple candidate
PANs exist, the End Device will select the PAN whose transmission link quality is the
strongest. If no valid Coordinator is found, the End Device will either go to sleep (as dictated
by its SM (Sleep Mode) parameter) or retry Association.
Note - An End Device will also disqualify Coordinators if they are not allowing
association (A2 - AllowAssociation bit); or, if the Coordinator is not using the same
NonBeacon scheme as the End Device. (They must both be programmed with NonBeacon
code.)
3. Associate to Valid Coordinator
Once a valid Coordinator is found (step 2), the End Device sends an Association
Request message to the Coordinator. It then waits for an Association Confirmation to be sent
from the Coordinator. Once the Confirmation is received, the End Device is Associated and
the Associate LED will blink rapidly (2 times per second). The LED is solid if the End
Device has not associated.
4. End Device Changes once an End Device has associated
Changing A1, ID or CH parameters will cause the End Device to disassociate and
restart the Association procedure.
If the End Device fails to associate, the AI command can give some indication of the
failure.
6.8 Zigbee Addressing:
Every RF data packet sent over-the-air contains a Source Address and Destination
Address field in its header. The RF module conforms to the 802.15.4 specification and
supports both short 16-bit addresses and long 64-bit addresses. A unique 64-bit IEEE source
address is assigned at the factory and can be read with the SL (Serial Number Low) and SH
(Serial Number High) commands. Short addressing must be configured manually. A module
will use its unique 64-bit address as its Source Address if its MY (16-bit Source Address)
value is “0xFFFF” or “0xFFFE”. To send a packet to a specific module using 64-bit
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addressing: Set Destination Address (DL + DH) to match the Source Address (SL + SH) of
the intended destination module. To send a packet to a specific module using 16-bit
addressing: Set DL (Destination Address Low) parameter to equal the MY parameter and set
the DH (Destination Address High) parameter to ‘0’.
6.8.1 Unicast Mode
By default, the RF module operates in Unicast Mode. Unicast Mode is the only mode
that supports retries. While in this mode, receiving modules send an ACK
(acknowledgement) of RF packet reception to the transmitter. If the transmitting module does
not receive the ACK, it will re-send the packet up to three times or until the ACK is received.
Short 16-bit addresses.
The module can be configured to use short 16-bit addresses as the Source Address by
setting (MY < 0xFFFE). Setting the DH parameter (DH = 0) will configure the Destination
Address to be a short 16-bit address (if DL < 0xFFFE). For two modules to communicate
using short addressing, the Destination Address of the transmitter module must match the
MY parameter of the receiver. The following table shows a sample network configuration
that would enable Unicast Mode communications using short 16-bit addresses.
Table 6.7: Unicast Network Configuration (using 16-bit addressing)
Parameter RF Module 1 RF Module 2
MY(source address) 0x01 0x02
DH(Destination High) 0 0
DL(Destination Low) 0x02 0x01
Long 64-bit addresses:
The RF module’s serial number (SL parameter concatenated to the SH parameter)
can be used as a 64-bit source address when the MY (16-bit Source Address) parame-ter is
disabled. When the MY parameter is disabled (set MY = 0xFFFF or 0xFFFE), the module’s
source address is set to the 64-bit IEEE address stored in the SH and SL parameters. When an
End Device associates to a Coordinator, its MY parameter is set to 0xFFFE to enable 64- bit
addressing. The 64-bit address of the module is stored as SH and SL parameters. To send a
packet to a specific module, the Destination Address (DL + DH) on one module must match
the Source Address (SL + SH) of the other.
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6.8.2 Broadcast Mode:
Any RF module within range will accept a packet that contains a broadcast address.
When configured to operate in Broadcast Mode, receiving modules do not send ACKs
(Acknowledgements) and transmitting modules do not automatically re-send packets as is the
case in Unicast Mode. To send a broadcast packet to all modules regardless of 16-bit or 64-
bit addressing, set the destination addresses of all the modules as shown below.
Sample Network Configuration (All modules in the network):
• DL (Destination Low Address) = 0x0000FFFF
• DH (Destination High Address) = 0x00000000 (default value)
6.8Modes of Operation
The Transceiver operates in five modes .They are
1. Idle Mode
2. Receive mode
3. Transmit Mode
4. Sleep Mode
5. Command Mode
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Fig: 6.7 Different Modes of Operation
The operation of Transceiver in each mode is explained below
1. Idle mode
When not receiving or transmitting data, the RF module is in Idle Mode. The module
shifts into the other modes of operation under the following conditions:
Transmit Mode (Serial data is received in the DI Buffer)
Receive Mode (Valid RF data is received through the antenna)
Sleep Mode (Sleep Mode condition is met)
Command Mode (Command Mode Sequence is issued)
Transmit Mode RF data packets:
When not receiving or transmitting data, the RF module is in Idle Mode. The module
shifts into the each transmitted data packet contains a Source Address and Destination
Address field. The Source Address matches the address of the transmitting module as
specified by the MY (Source Address) parameter (if MY >= 0xFFFE), the SH (Serial
Number High) parameter or the SL (Serial Number Low) parameter. The <Destination
Address> field is created from the DH (Destination Address High) and DL (Destination
Address Low) parameter values. The Source Address and/or Destination Address fields will
either contain a 16-bit short or long 64-bit long address.
There are two methods to transmit data. They are
1. Direct Transmission
If the source address matches the destination address then Data is transmitted
immediately to the Destination Address. A NonBeaconing Coordinator can be configured to
use only Direct Transmission by setting the SP (Cyclic Sleep Period) parameter to “0”. Also,
a NonBeaconing Coordinator using indirect transmissions will revert to direct transmission if
it knows the destination module is awake. To enable this behavior, the ST (Time before
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Sleep) value of the Coordinator must be set to match the ST value of the End Device. Once
the End Device either transmits data to the Coordinator or polls the Coordinator for data, the
Coordinator will use direct transmission for all subsequent data transmissions to that module
address until ST time (or number of beacons) occurs with no activity (at which point it will
revert to using indirect transmissions for that module address). “No activity” means no
transmission or reception of messages with a specific address. Global messages will not reset
the ST timer.
2. Indirect Transmission
A packet is retained for a period of time and is only transmitted after the destination
module (Source Address = Destination Address) requests the data. To configure Indirect
Transmissions in a PAN (Personal Area Network), the SP (Cyclic Sleep Period) parameter
value on the Coordinator must be set to match the longest sleep value of any End Device. The
SP parameter represents time in NonBeacon systems and beacons in Beacon-enabled
systems. The sleep period value on the Coordinator determines how long (time or number of
beacons) the Coordinator will retain an indirect message before discarding it. In NonBeacon
networks, an End Device must poll the Coordinator once it wakes from Sleep to determine if
the Coordinator has an indirect message for it. For Cyclic Sleep Modes, this is done
automatically every time the module wakes (after SP time). For Pin Sleep Modes, the A1
(End Device Association) parameter value must be set to enable Coordinator polling on pin
wake-up. Alternatively, an End Device can use the FP (Force Poll) command to poll the
Coordinator as needed.
Indirect Transmissions can only occur on a Coordinator. Thus, if all nodes in a
network are End Devices, only Direct Transmissions will occur. Indirect Transmissions are
useful to ensure packet delivery to a sleeping node. The Coordinator currently is able to retain
up to 2 indirect messages.
CCA (Clear Channel Assessment)
Prior to transmitting a packet, a CCA (Clear Channel Assessment) is performed on the
channel to determine if the channel is available for transmission. The detected energy on the
channel is compared with the CA (Clear Channel Assessment) parameter value. If the
detected energy exceeds the CA parameter value, the packet is not transmitted. Also, a delay
is inserted before a transmission takes place. This delay is settable using the RN (Back off
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Exponent) parameter. If RN is set to “0”, then there is no delay before the first CCA is
performed. The RN parameter value is the equivalent of the “minBE” parameter in the
802.15.4 specification. The transmit sequence follows the 802.15.4 specification. By default,
the MM (MAC Mode) parameter = 0. On a CCA failure, the module will attempt to resend
the packet up to two additional times. When in Unicast packets with RR (Retries) = 0, the
module will execute two CCA retires. Broadcast packets always get two CCA retires.
Acknowledgement
If the transmission is not a broadcast message, the module will expect to receive an
acknowledgement from the destination node. If an acknowledgement is not received, the
packet will be resent up to 3 more times. If the acknowledgement is not received after all
transmissions, an ACK failure is recorded.
Sleep Mode
Sleep Modes enable the RF module to enter states of low-power consumption when not in use. In order to enter Sleep Mode, one of the following conditions must be met (in addition to the module having a non-zero SM parameter value):
Sleep_RQ (pin 9) is asserted.
The module is idle (no data transmission or reception) for the amount of time defined
by the ST (Time before Sleep) parameter. (ST is only active when SM = 4-5).
The SM command is central to setting Sleep Mode configurations. By default, Sleep Modes are disabled (SM = 0) and the module remains in Idle/Receive Mode. When in this state, the module is constantly ready to respond to serial or RF activity.Higher Voltages
Sleep Mode current consumption is highly sensitive to voltage. Voltages above 3.0V
will cause much higher current consumption.
Command mode
To modify or read RF Module parameters, the module must first enter into Command
Mode – a state in which incoming characters are interpreted as commands. Two Command
Mode options are supported: AT Command Mode and API Command Mode.
6.8 AT Command Mode
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To Enter AT Command Mode:
Send the 3-character command sequence “+++” and observe guard times before and
after the command characters.
AT Command Mode Sequence (for transition to Command Mode):
No characters sent for one second [GT (Guard Times) parameter = 0x3E8].
Input three plus characters (“+++”) within one second [CC (Command Sequence
Character) Parameter = 0x2B].
No characters sent for one second [GT (Guard Times) parameter = 0x3E8].
All of the parameter values in the sequence can be modified to reflect user
preferences.
To Send AT Commands:
Fig: 6.8 Syntax for sending AT Commands
The preceding example would change the RF module Destination Address (Low) to
“0x1F”. To store the new value to non-volatile (long term) memory, subsequently send the
WR (Write) command. For modified parameter values to persist in the module’s registry after
a reset, changes must be saved to non-volatile memory using the WR (Write) Command.
Otherwise, parameters are restored to previously saved values after the module is reset.
System Response
When a command is sent to the module, the module will parse and execute the
command. Upon successful execution of a command, the module returns an “OK” message.
If execution of a command results in an error, the module returns an “ERROR” message.
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To Exit AT Command Mode:
1. Send the ATCN (Exit Command Mode) command (followed by a carriage return).
2. If no valid AT Commands are received within the time specified by CT (Command Mode
Timeout) Command, the RF module automatically returns to Idle Mode.
6.8.1 AT Commands Description:
SH (Serial Number High) Command
The SH command is used to read the high 32 bits of the RF module's unique IEEE
64-bit address. The module serial number is set at the factory and is read-only.
AT Command: ATSH
Parameter Range: 0 - 0xFFFFFFFF [read-only]
Related Commands: SL (Serial Number Low), MY (Source Address).
SL (Serial Number Low) Command
The SL command is used to read the low 32 bits of the RF module's unique IEEE 64-
bit address. The module serial number is set at the factory and is read-only.
AT Command: ATSL
Parameter Range: 0 - 0xFFFFFFFF [read-only]
Related Commands: SH (Serial Number High), MY (Source Address)
DH (Destination Address High) Command
The DH command issued to set and read the upper 32 bits of the RF module's 64-bit
destination address. When combined with the DL (Destination Address Low) parameter, it
defines the destination address used for transmission.
A module will only communicate with other modules having the same channel (CH
parameter); PAN ID (ID parameter) and destination address (DH + DL parameters).
To transmit using a 16-bit address, set the DH parameter to zero and the DL
parameter less than 0xFFFF. 0x000000000000FFFF (DL concatenated to DH) is the
broadcast address for the PAN.
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AT Command: ATDH
Parameter Range: 0 - 0xFFFFFFFF
Default Parameter Value: 0
Related Commands: DL (Destination Address Low), CH (Channel), ID (PAN VID)
DL (Destination Address Low) Command
The DL command is used to set and read the lower 32 bits of the RF module's 64-bit
destination address. When combined with the DH (Destination Address High) parameter, it
defines the destination address used for transmission. A module will only communicate with
other modules having the same channel (CH parameter), PAN ID (ID parameter) and
destination address (DH + DL parameters).
To transmit using a 16-bit address, set the DH parameter to zero and the DL
parameter less than 0xFFFF. 0x000000000000FFFF (DL concatenated to DH) is the
broadcast address for the PAN.
AT Command: ATDL
Parameter Range: 0 - 0xFFFFFFFF
Default Parameter Value: 0
Related Commands: DH (Destination Address High), CH (Channel), ID (PAN VID)
DN (Destination Node) Command
The DN command is used to resolve a NI (Node Identifier) string to a physical
address. The following events occur upon successful command execution:
1. DL and DH are set to the address of the module with the matching NI (Node Identifier).
2. ‘OK’ is returned.
3. RF module automatically exits AT Command Mode.
If there is no response from a modem within 200 msec or a parameter is not specified
(left blank), the command is terminated and an ‘ERROR’ message is returned.
AT Command: ATDN
Parameter Range: 20-character ASCII String
Minimum Firmware Version Required: v1.x80
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BD (Interface Data Rate) Command
The BD command is used to set and read the serial interface data rate used between
the RF module and host. This parameter determines the rate at which serial data is sent to the
module from the host. Modified interface data rates do not take effect until the CN (Exit AT
Command Mode) command is issued and the system returns the 'OK' response.
When parameters 0-7 are sent to the module, the respective interface data rates are
used. The RF data rate is not affected by the BD parameter. If the interface data rate is set
higher than the RF data rate, a flow control configuration may need to be implemented.
AT Command: ATBD
Parameter Range: 0 - 7 (standard rates) 0x80-0x1C200 (non-standard rates)
Table: 6.6 Setting Different Baud Rate
Parameter Configuration (bps)0 12001 24002 48003 96004 192005 384006 576007 115200
Default Parameter Value: 3
CE (Coordinator Enable) Command
The CE command is used to set and read the behavior (End Device vs. Coordinator)
of the RF module.
AT Command: ATCE
Parameter Range: 0 – 1
Table: 6.7 Configuring the RF Module
Parameter Configuration0 End device1 Coordinator
Default Parameter Value: 0
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Minimum Firmware Version Required: v1.x80
CH (Channel) Command
The CH command is used to set/read the operating channel on which RF connections
are made between RF modules. The channel is one of three addressing options available to
the module. The other options are the PAN ID (ID command) and destination addresses (DL
& DH commands).
In order for modules to communicate with each other, the modules must share the
same channel number. Different channels can be used to prevent modules in one network
from listening to transmissions of another. Adjacent channel rejection is 23 dB.
The module uses channel numbers of the 802.15.4 standard.
Center Frequency = 2.405 + (CH - 11d) * 5 MHz (d = decimal)
AT Command: ATCH
Parameter Range: 0x0B - 0x1A (XBee) 0x0C - 0x17 (XBee-PRO)
Default Parameter Value: 0x0C (12 decimal)
Related Commands: ID (PAN ID), DL
(Destination Address Low, DH (Destination Address High)
ID (Pan ID) Command
The ID command is used to set and read the PAN (Personal Area Network) ID of the
RF module. Only modules with matching PAN IDs can communicate with each other.
Unique PAN IDs enable control of which RF packets are received by a module.
Setting the ID parameter to 0xFFFF indicates a global transmission for all PANs. It
does not indicate a global receives.
AT Command: ATID
Parameter Range: 0 - 0xFFFF
Default Parameter Value: 0x3332 (13106 decimal)
MY (16-bit Source Address) Command
The MY command is used to set and read the 16-bit source address of the RF module.
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By setting MY to 0xFFFF, the reception of RF packets having a 16-bit address is disabled.
The 64-bit address is the module’s serial number and is always enabled.
AT Command: ATMY
Parameter Range: 0 - 0xFFFF
Default Parameter Value: 0
Related Commands: DH (Destination Address High), DL (Destination Address Low), CH
(Channel), ID (PAN ID)
NI (Node Identifier) Command
The NI command is used to set and read a string for identifying a particular node.Rules:
Register only accepts printable ASCII data.
A string cannot start with a space.
A carriage return ends command
Command will automatically end when maximum bytes for the string have been
entered.
This string is returned as part of the ND (Node Discover) command. This identifier is
also used with the DN (Destination Node) command.
AT Command: ATNI
Parameter Range: 20-character ASCII string
Related Commands: ND (Node Discover), DN (Destination Node)
Minimum Firmware Version Required: v1.x80
WR (Write) Command
The WR command is used to write configurable parameters to the RF module's
nonvolatile memory. Parameter values remain in the module's memory until overwritten by
subsequent use of the WR Command.
If changes are made without writing them to non-volatile memory, the module reverts
back to previously saved parameters the next time the module is powered-on.
AT Command: ATWR
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VR (Firmware Version) Command
The VR command is used to read which firmware version is stored in the module.
XBee version numbers will have four significant digits. The reported number will show three
or four numbers and is stated in hexadecimal notation. A version can be reported as "ABC"
or "ABCD". Digits ABC are the main release number and D is the revision number from the
main release. "D" is not required and if it is not present, a zero is assumed for D. "B" is a
variant designator. The following variants exist:
• "0" = Non-Beacon Enabled 802.15.4 Code
• "1" = Beacon Enabled 802.15.4 Code
AT Command: ATVR
Parameter Range: 0 - 0xFFFF [read only]
AP (API Enable) Command
The AP command is used to enable the RF module to operate using a frame based
API instead of using the default Transparent (UART) mode.
AT Command: ATAP
Parameter Range: 0 – 2
Table: 6.8 Enabling AP Command
Parameter Configuration0 Disabled (transparent operation )1 API enabled2 API enabled(with escaped characters)
Default Parameter Value: 0
Minimum Firmware Version Required: v1.x80
EA (ACK Failures) Command
The EA command is used to reset and read the count of ACK (acknowledgement)
failures. This parameter value increment when the module expires its transmission retries
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without receiving an ACK on a packet transmission. This count saturates at its maximum
value. Set the parameter to “0” to reset count.
AT Command: ATEA
Parameter Range: 0 - 0xFFFF
Minimum Firmware Version Required: v1.x80
EC (CCA Failures) Command
The EC command is used to read and reset the count of CCA (Clear Channel
Assessment) failures. These parameter value increments when the RF module does not
transmit a packet due to the detection of energy that is above the CCA threshold level (set
with CA command). This count saturates at its maximum value.
Set the EC parameter to “0” to reset count.
AT Command: ATEC
Parameter Range: 0 - 0xFFFF
Related Command: CA (CCA Threshold)
Minimum Firmware Version Required: v1.x80
EE (AES Encryption Enable) Command
The EE command is used to set/read the parameter that disables/enables 128-bit AES
encryption. The XBee/XBee-PRO firmware uses the 802.15.4 Default Security protocol and
uses AES encryption with a 128-bit key. AES encryption dictates that all modules in the
network use the same key and the maximum RF packet size is 95 Bytes.
When encryption is enabled, the module will always use its 64-bit long address as the
source address for RF packets. This does not affect how the MY (Source Address), DH
(Destination Address High) and DL (Destination Address Low) parameters work.
AT Command: ATEE
Parameter Range: 0 - 1
Default Parameter Value: 0
Related Commands: KY (Encryption Key), AP (API Enable), MM (MAC Mode) Minimum
Firmware Version Required: v1.xA0
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VL (Firmware Version - Verbose)
The VL command is used to read detailed version information about the RF module.
The information includes:
Application builds date; MAC, PHY and boot loader versions; and builds dates.
AT Command: ATVL
Parameter Range: 0 - 0xFF
Default Parameter Value: 0x28 (40 decimal)
Minimum Firmware Version Required: v1.x80
ND (Node Discover) Command
The ND command is used to discover and report all modules on its current operating
channel (CH parameter) and PAN ID (ID parameter). ND also accepts an NI (Node
Identifier) value as a parameter. In this case, only a module matching the supplied identifier
will respond.
ND uses a 64-bit long address when sending and responding to an ND request. The
ND command causes a module to transmit a globally addressed ND command packet. The
amount of time allowed for responses is determined by the NT (Node Discover Time)
parameter.
AT Command: ATND
Range: optional 20-character NI value
Related Commands: CH (Channel), ID (Pan ID), MY (Source Address), SH (Serial Number
High), SL (Serial Number Low), NI (Node Identifier), NT (Node Discover Time)
Minimum Firmware Version Required: v1.x80
AC (Apply Changes) Command
The AC command is used to explicitly apply changes to module parameter values.
‘Applying changes’ means that the module is re-initialized based on changes made to its
parameter values. Once changes are applied, the module immediately operates according to
the new parameter values.
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This behavior is in contrast to issuing the WR (Write) command. The WR command
saves parameter values to non-volatile memory, but the module still operates according to
previously saved values until the module is re-booted or the CN (Exit AT Command Mode)
command is issued.
AT Command: ATAC
Minimum Firmware Version Required: v1.xA0
RE (Restore Defaults) Command
The RE command is used to restore all configurable parameters to their factory
default settings. The RE command does not write restored values to non-volatile (persistent)
memory. Issue the WR (Write) command subsequent to issuing the RE command to save
restored parameter values to non-volatile memory.
AT Command: ATRE
HV (Hardware Version) Command
The HV command is used to read the hardware version of the RF module.
AT Command: ATHV
Parameter Range: 0 - 0xFFFF [Read-only]
Minimum Firmware Version Required: v1.x80
CN (Exit Command Mode) Command
The CN command is used to explicitly exit the RF module from AT Command Mode.
AT Command: ATCN
6.9 ZIGBEE ARCHITECTURE
The IEEE 802.15.4 standard and Zigbee wireless network technology are ideal for the
implementation of a wide range of low cost, low power and reliable control and monitoring
applications within the private home and industrial environment. The working model of the
IEEE 802.15.4 and Zigbee is illustrated in Figure 6.9.
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Fig: 6.9 Zigbee Architecture
In the Zigbee architecture, the PHY layer and MAC layer are based on the IEEE
802.15.4 WPAN standard. Zigbee defines the NWK and APS layers. The software and
hardware vendor will provide the software stack with appropriate tools to allow an OEM to
create applications, which are added to the APL. The Physical (PHY) layer and Medium
Access Control (MAC) layer are based on the IEEE802.15.4 PAN standard. This includes the
actual radio hardware. Above the MAC and PHY are the Network (NWK) and application
layers defined by Zigbee.
The first two layers, the physical (PHY) and Medium Access Control (MAC) are
defined in the IEEE standard. The other layers that build on the PHY and MAC layers are
defined by the Zigbee alliance.
The PHY layer contains the RF transceiver and access to the other hardware and
control mechanisms. The function of the PHY is to activate and deactivate the radio
transceiver and other hardware specific services such as access to the channels.
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The MAC layer is as described by the name a controlling device for radio medium. It
controls access to the physical radio channel and other services defined by the PHY service.
It is also responsible for a reliable transmission system through its services. The services are
about channel access and transmission techniques and validation of data packets.
The network (NWK) layer is responsible for the network controlling functions. It
controls the mechanism for joining and leaving a network and for creating a network for
those devices which have the capability to do so. The NWK layer applies also security to
what is going to be data packets. The NWK layer is responsible for discovery and storing
information about the neighbors in the network. Responsibility for routing between devices
and routing of packets to their destination goes to this layer.
The application layer (APL) consists of three different blocks which have different
functionalities and responsibilities. The application support sub-layer (APS) is responsible for
maintaining a table of devices that are connected to each other, a binding table. The APS
layer provides an interface between the NWK layer and the APL with its set of services.
The Zigbee device object (ZDO) is responsible for managing Zigbee devices in the
network. This could be discovering new device in the network and define its role in the
network it also determines the services the new device provides. Possible device types are
those defined in Zigbee standard and they are coordinators, routers and end devices. The
Application Frame (AF) contains application objects which can be manufacturer defined
application objects. An example of an application object is a power switch.
The security service provider (SSP) provides enhanced security options as encryption
with 128-bit key transport.
PHYSICAL LAYER
The physical layer is responsible for the radio hardware device. The standard defines
two hardware Platforms for the IEEE 802.15.4. One describes the 2.4 GHz spectrum and one
the 868/915 MHz spectrum.The lower band use different modulations technique and lower
data rate. Explanations for the different bands are given in the regulations section. The lower
band provides better radio performance when reviewing the frequency band and the antenna
performance .specifications in the rest of the report apply only for the 2.4GHz band.
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Frequency bands:Table: 6.9 Operating Frequency Bands of Zigbee
PHY(MHz)
FrequencyBand
(MHz)
Spreading parameters Data parameters
Chip rate(k chips/s)
Modulation Bit rate
(kb/s)
Symbol rate(k symbol/s)
symbols channels
865/915
868-868.6 300 BPSK 20 20 Binary 0
902-928 600 BPSK 40 40 Binary 1-10
2400 2400-2483.5
2000 O-QPSK 250 62.5 16-aryOrthogo
nal
11-26
ResponsibilityThe layer is responsible for the hardware and can be divided into the following tasks:
Activation and deactivation of radio transceiver.
Data transmission and reception.
Channel frequency selection.
Indicator for radio quality within channels and for packets.
Channel access assessment technique.
Layer service
The PHY data service is responsible of transport of MPDU between MAC peer sub-
layers through the PD-SAP. This is done by data primitives such as PD-DATA request. The
PLME is responsible for managing a database of managed objects by the PHY. It is referred
to as PHY information base (PIB). The PLME-SAP is responsible for management
commands between the MAC layer management entity (MLME) and the PLME. The
primitives that are provided are defined for the PLME. They provide for example performing
CCA, Energy Detection (ED) measurements or accessing the PIB data base.
PHY enumeration descriptions, constants and PIB attributes are defined in a table in
the standard. The maximum PSDU that the PHY shall be able to receive from the MAC layer
is 127 octets as described in the introduction. Turnaround times for TX-to-RX and RX-to-TX
shall be a maximum of 12 data symbol periods. Each symbol is 4 bits which gives a
maximum turnaround time of 6 octet periods.
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The spreading of the data decreases the raw data transfer but leads to a much higher
reliability in the transmission. Errors in the baseband chip sequence do not mean errors in the
raw data. The probability to recognize the correct symbol even if bit errors have occurred is
high. The O-QPSK modulation used is equivalent to MSK modulation. It utilizes constant
amplitude and enables use of relatively nonlinear amplifier designs which means more simple
and low cost construction.
MAC LAYERThe MAC layer is responsible for accessing the physical radio channel through the
PHY layer. It provides services to enable reliable single –hop communication links between
devices in a network. The services are about channel access and transmission techniques and
validation of data packets.
Layer ServiceThe services provided by the MAC layer can be divided into these sub groups:
Providing a single-hop peer link between MAC entities.
Supporting PAN association and dissociation.
Using CSMA-CA mechanism for channel access.
Handling and maintaining of GTS mechanism.
Generate network beacons if device is coordinator.
Synchronization to network beacons.
Supporting device security.
Layer Structure The structure communication model is similar to the PHY layer. The MAC layer
includes a management entity (MLME) which provides interface to management entities on
other devices. The MLME is also responsible of maintaining a data base of management
objects. The MAC sub-layer provides two services accessed through the data entity and
management. The services are provided for the PHY layer and next higher layer. Data
services provided by the MAC layer are those for requesting and confirming data for
example. Management services in the MAC layer is among others association primitives,
beacon primitives and channel scanning primitives.
CSMA-CA The CSMA-CA algorithm implements time units called backoff periods. In slotted
CSMA-CA the backoff periods of every device in the network are aligned with the super
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frame boundaries of the coordinator. In the unslotted CSMA-CA the backoff periods of
devices in the network are not related in time to any other device 9in the PAN.
The IEEE 802.15.4 MAC sub layer controls the access to the radio channel using the
CSMA-CA (Carrier Sense Multiple Access with Collision Avoidance) method, and handles
network (dis)association and MAC layer security (AES-128 encryption based). It is also
responsible for flow control via acknowledgement and retransmission of data packets, frame
validation, and network synchronization as well as support to upper layers for robust link
operation. The Zigbee wireless technology specifies the network, security, and application
layers upon the IEEE 802.15.4 PHY and MAC layers. The Zigbee Alliance also provides
interoperability and conformance testing specifications.
Channel Access
There are two types of channel access in the IEEE 802.15.4 defined communication
system. They are based on contention which decides if the devices retain their own time slot
for communication. The contention based allows the devices to access channel in the
distributed way using CSMA-CA algorithm. With this contention free method the network
coordinator decides about the channel access with the use of Guaranteed Time Slots (GTS) of
the channel space. This contention free method is suitable for latency sensitive devices that
require short delay time and no competition of the channel access.
TransmissionTransmission, reception and acknowledgements are procedures for sending data,
receiving data and for acknowledging that data has been received or sent. Retransmission of
data if error occurs if bounded to acknowledgments procedures that are optional.
SecurityThe MAC layer is responsible for providing security services when requested by
higher layers. The higher layers are responsible for information necessary to provide needed
security services. Key management, device authentication and freshness protection may be
services provided by higher layers but out of the scope for this standard..
The IEEE 802.15.4 supports the following security services: Access control
Data encryption
Frame integrity
Sequential freshness
The security can be implemented on both incoming and outgoing frames.
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Access control provides and maintains an Access Control List (ACL). The list
contains devices that have been selected and approved for communicating with. Data
encryption security service uses a symmetric cipher to encrypt data for parties who do not
have the cryptographic key. In this standard the data encryption may be provided on beacon
payloads, command payloads and data payloads. Frame integrity service provides assurance
that data have not been modified by parties without the cryptographic key and also that data
originates from sources with the key. The service may be provided on beacon frames,
command frames and data frames. Sequential freshness uses a sequence to protect from
frames that are not the original in some manner.
NETWORK LAYER
The NWK layer is the first Zigbee layer. It is build upon the MAC and PHY layers.
The NWK layer provides services for routing and multi-hop communication needed to build
different network topologies it is required for correct functionality for underlying layers. It
acts as a interface for next higher layer, the application layer. It includes a NWK layer
management entity (NLME). The NLME and the NWK layer data entity (NLDE) uses the
NLME-SAP and the NLDE-SAP for communicating to other layers.
The NLDE provides two kinds of services Generate NWK Protocol Data Unit (NPDU) from next higher layer, APS layer.
Deliver NPDU to recipient or route it to the next step towards the destination.
The NLME provides the following services: Configuring a new device
Starting a network
Joining and leaving a network
Addressing
Neighbour discovery
Route discovery
Reception control
Attributes
A list of constants is characterizing the NWK layer. A list of attributes is also given
and it is used to manage the NWK layer of a device. An attribute is a data entity that
represents a physical quantity or a state. The attribute data is sent using commands.
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Building network
The procedures for building networks are build on those defined in the MAC layer.
Only coordinators are able to build a network. After that is guaranteed an ED scan is
performed followed by an active scan. When data is processed a PAN identifier is selected,
channel selection are made and a network address is assigned.
Joining network
Coordinators and routers can permit devices to join the network. The relationship
between the device that provides permission and the device that wants to join the network is
called a parent-child relationship. A parent can directly accept a child and join it to the
network with the 64 bit IEEE address. The child retains then a short logical address. When a
device wants to join a network first a scan procedure is performed. A suitable parent is
searched for from the neighbour table. Joining the network is then done by an association
request. If joining was successful the new device receives a 16 bit short address for
communication within the network. The devices are then updating the information in their
neighbour tables. Orphaning is the procedure that is performed when a child loose connection
to its network or to its parent.
The leaving of a network can be done either by request from the child or as a request
from the parent to force the child device to leave the network. Every device has an associated
depth. It tells the minimum hops a data frame has to perform through parent links to reach the
coordinator. The coordinator itself has 0 depth and its children have 1 depth. The maximum
depth of the network is decided by the coordinator. Neighbour tables shall contain
information about devices within a specified transmission range. The information shall be
used for different purpose and contains basic device and network information. It can also be
increased with more information. A table entry shall be updated each time a device receives a
frame from the neighbour.
The addressing of joined devices can be assigned in two ways. Either as distributed
address assignment mechanism or as higher-layer address assignment mechanism.
APL LAYER
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The application layer is the second of two Zigbee layers. The application layer houses
the responsibility for overall device management. It is also responsible for applications and
service function within the application layer and to the NWK layer. The application layer
consists of the APS, AF and ZDO.
There are two addressing concepts for Zigbee devices. It consists of addressing the
specific radio hardware or the application object. They are called node addressing respective
endpoint addressing. A node refers to a single radio device. A node could consist of several
subunits where each subunit has a device description. Each subunit is assigned its own
specific endpoint which range from 1 to 240. Each endpoint has a description that describes
for example what it does and which attributes it has. Attributes are variables that represent
physical quantity or states. In a typical application an attribute could be temperature and
endpoints could be sensor applications for temperature and humidity. A cluster is identifier of
messages that are sent and are also container for attributes. A Zigbee device would then
represent a node that could be an indoors climate report station and another Zigbee device
node a controller and communication central for a climate control centre.
Application support sub-layer (APS)
The APS provides interface between the NWK layer and application layer. The
services are offered via the two services, APS Data Entity (APSDE) and APS Management
Entity (APSME). The APSDE provides data transmission through its APSDE-SAP and the
management entity provides all other services through APSME-SAP.
The APSDE provides these services Generation of APDU-APS layer specific frame are generated
Binding-Transmission between matched devices
The APSME provides these services: Interaction with Zigbee Stack
Binding-Ability to match devices
Security-Security relationships with use of keys
Transmission
If an indirect transmission is sent the originating device shall direct the transmission
to the Zigbee coordinator which handles message reflection. The Zigbee coordinator contains
the binding table and shall search for table entry that matches the source address, the cluster
identifier or the source endpoint field. The transmission shall be directed to each of these
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matched entries. The source address is retained from the NWK layer, the cluster identifier
and the source endpoint is included in the frame. The indirect transmission shall include the
source endpoint or destination endpoint field depending on direction with respect to the
coordinator. If the transmission is towards the coordinator for relay it shall contain
destination endpoint. If it is directed from coordinator after relay it shall contain the source
endpoint. Acknowledgement is optional and in indirect addressing the coordinator shall
answer acknowledgement request from originating devices and requesting acknowledgement
from devices that frames are relayed to. Retransmissions are bound to acknowledgement.
When acknowledge is enabled retransmission shall be performed if error occurs.
Application Framework (AF)The application frame work is containing the application objects and provides
services that the application uses. The applications communicate through the APSDE-SAP.
The control and management of application frame is performed by ZDO public interfaces.
The primitives is as for the APS sub-layer request, confirm and indication.
Endpoints
The application framework can house up to 240 application objects. Each one is
defined on an endpoint with index from 1 to 240, see figure 2.13. Endpoint 0 is reserved and
is used for interface to the ZDO and endpoint 255 is reserved for broadcasting of data to all
application objects.
ZDO The ZDO is responsible for overall device management and handling of services. It
uses its services to implement three different logical Zigbee devices, coordinator, router and
end device. The ZDO is interfacing the management entities of the NWK and the APS sub-
layer.
The ZDO is responsible for assembling data configuration from end points to
implement these functions:
Device and service discovery
Security manager
Network manager
Node manager
LATCH
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The 74LS244 are Octal Buffers and Line Drivers designed to be employed as memory
address drivers, clock drivers and bus-oriented transmitters/receivers which provide improved
PC board density. The designer has a choice of selected combinations of inverting and non
inverting outputs, symmetrical, active-low output-control (G) inputs, and complementary
output-control (G and G) inputs. These devices feature high fan-out, improved fan-in, and
400-mV noise margin.
Hysteresis at Inputs to Improve Noise Margins
3-State Outputs Drive Bus Lines or Buffer Memory Address Registers
Input Clamp Diodes Limit High-Speed Termination Effects
Logic and pin connection diagram:
Truth table:
LANDMINE DETECTOR:
=== Modern developments ===
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The modern development of the LANDMINE detector began in the 1930s. [[Gerhard Fisher]] had developed a system of radio direction-finding, which was to be used for accurate navigation. The system worked extremely well, but Fisher noticed that there were anomalies in areas where the terrain contained ore-bearing rocks. He reasoned that if a radio beam could be distorted by LANDMINE, then it should be possible to design a machine which would detect LANDMINE using a search coil resonating at a radio frequency. In 1937 he applied for, and was granted, the first patent for a LANDMINE detector. However, it was one [[Lieutenant]] [[Józef Kosacki|Jozef Stanislaw Kosacki]], a Polish officer attached to a unit stationed in [[St Andrews]], [[Fife]], [[Scotland]] during the early years of [[World War II]], that refined the design into a practical [[Polish mine detector]].<ref>"The Polish Contribution to The Ultimate Allied Victory in The Second World War" Tadeusz Modelski, Worthing, England 1986, Page 221</ref> They were heavy, ran on vacuum tubes, and needed separate battery packs.
The design invented by Kosacki was used extensively during the clearance of the German mine fields during the [[Second Battle of El Alamein]] when 500 units were shipped to [[Bernard Montgomery, 1st Viscount Montgomery of Alamein|Field Marshal Montgomery]] to clear the minefields of the retreating Germans, and later used during the [[Allied invasion of Sicily]], the [[Allied invasion of Italy]] and the [[Invasion of Normandy]]. <ref>"The History of Landmines" by Mike Croll published in Great Britain in 1998 by Leo Cooper, Pen & Sword Books Ltd. ISBN 0850522680</ref>As it was a wartime research operation to create and refine the design of the detector, the knowledge that Stanislaw created the first practical LANDMINE detector was kept secret for over 50 years.
After the war, there were plenty of surplus mine detectors on the market; they were bought up by relic hunters who used them for fun and profit. This helped to form LANDMINE detecting into a hobby.
Description
This is the circuit diagram of a low cost LANDMINE detector using a single transistor circuit and an old pocket radio..This is nothing but a Colpitts oscillator working in the medium band frequency and a radio tuned to the same frequency.First the radio and the circuit are placed close.Then the radio is tuned so that there is no sound from radio.In this condition the radio and the circuit will be in same frequency and same frequencies beat off to produce no sound.This is the set up.When the LANDMINE detector circuit is placed near to a LANDMINE object the inductance of its coil changes , and so do the frequency of oscillations.Now the two frequency will be different , there will be no canceling and radio produces a hissing sound.The LANDMINE is detected. Turck is offering its innovative Uprox+sensor line that it believes will set a new standard for LANDMINE detection. Uprox+sensors are capable of precisely detecting materials such as iron steel, stainless steel, copper, aluminium and brass at extended sensing distances without a reduction in the rated sensing distance of the sensor. Uprox+sensors are claimed to offer unrivalled performance due to a newly patented multicoil system. This multicoil system replaces the wound coil found in conventional ferrite core inductive sensors, resulting in extended sensing distances (up to 250% higher) and the flexibility to incorporate this technology in a variety of unique housing designs.
The sensors also feature an integrated pre-damping protection function to reduce the
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LANDMINE free mounting area in applications. This allows traditionally flush mounted sensors to be recessed by half a turn for increased mechanical protection. Non-flush mounted sensors may be embedded in LANDMINE up to the outer edge of the thread on barrel style sensors and on all four sides of rectangular style sensors, causing only a slight reduction in sensing distance.
All Uprox+proximity sensors adhere to the present EN50082-2 standard, yet they also exceed the strict provisions required by EN61000-4-6: an integral part of industry standards by the year 2006 and beyond. This protects against conducted interference from frequency converters, and other sources that produce a high level of EMI. Uprox+sensors provide a product that incorporates a multitude of sensing requirements; whether for the automotive industry, machine engineering or for transport and handling applications, Uprox+sensors are capable of replacing several conventional proximity sensors.
WEBCAM
"Webcam" refers to the technology generally; the first part of the term ("web-") is often
replaced with a word describing what can be viewed with the camera, such as a netcam or
streetcam.
Webcams are video capturing devices connected to computers or computer networks, often
using USB or, if they connect to networks, Ethernet or Wi-Fi. They are well-known for low
manufacturing costs and flexible applications.
Video capture is the process of converting an analog video signal—such as that produced by
a video camera or DVD player—to digital form. The resulting digital data are referred to as a
digital video stream, or more often, simply video stream. This is in contrast with screen
casting, in which previously digitized video is captured while displayed on a digital monitor
Webcams typically include a lens, an image sensor, and some support electronics. Various
lenses are available, the most common being a plastic lens that can be screwed in and out to
set the camera's focus. Fixed focus lenses, which have no provision for adjustment, are also
available. Image sensors can be CMOS or CCD, the former being dominant for low-cost
cameras, but CCD cameras do not necessarily outperform CMOS-based cameras in the low
cost price range. Consumer webcams are usually VGA resolution with a frame rate of 30
frames per second. Higher resolutions, in mega pixels, are available and higher frame rates
are starting to appear.
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The video capture process involves several processing steps. First the analog video signal is
digitized by an analog-to-digital converter to produce a raw, digital data stream. In the case of
composite video, the luminance and chrominance are then separated. Next, the chrominance
is demodulated to produce color difference video data. At this point, the data may be
modified so as to adjust brightness, contrast, saturation and hue. Finally, the data is
transformed by a color space converter to generate data in conformance with any of several
color space standards, such as RGB and YCbCr. Together, these steps constituted video
decoding, because they "decode" an analog video format such as NTSC or PAL.
Hardware Special electronic circuitry is required to capture video from analog video sources.
At the system level this function is typically performed by a dedicated video capture card.
Such cards often utilize video decoder integrated circuits to implement the video decoding
process.
Support electronics are present to read the image from the sensor and transmit it to the host
computer. The camera pictured to the right, for example, uses a Sonix SN9C101 to transmit
its image over USB. Some cameras - such as mobile phone cameras - use a CMOS sensor
with supporting electronics.
FEATURES:
Smallest wireless video & audio camera
Wireless transmission and reception
High sensitivity
Easy installation & operation
Easy to conceat
Light weight
Low power consumption
Small size
SPECIFICATIONS:
Output frequency: 900MHZ 1200MHZ
Output power: 50mW 200mW
Power supply: DC +6~12v
Distance covered: 10m
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REGULATED POWER SUPPLY
DESCRIPTION
A variable regulated power supply, also called a variable bench power supply, is one
where you can continuously adjust the output voltage to your requirements. Varying the
output of the power supply is the recommended way to test a project after having double
checked parts placement against circuit drawings and the parts placement guide.
This type of regulation is ideal for having a simple variable bench power supply.
Actually this is quite important because one of the first projects a hobbyist should undertake
is the construction of a variable regulated power supply. While a dedicated supply is quite
handy e.g. 5V or 12V, it's much handier to have a variable supply on hand, especially for
testing.
Most digital logic circuits and processors need a 5-volt power supply. To use these
parts we need to build a regulated 5-volt source. Usually you start with an unregulated power
supply ranging from 9 volts to 24 volts DC. To make a 5 volt power supply, we use a
LM7805 voltage regulator IC (Integrated Circuit). The IC is shown below.
The LM7805 is simple to use. You simply connect the positive lead of your
unregulated DC power supply (anything from 9VDC to 24VDC) to the Input pin, connect the
negative lead to the Common pin and then when you turn on the power, you get a 5 volt
supply from the Output pin.
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CIRCUIT FEATURES:
Brief description of operation:
ives out well regulated +5V output, output current capability of 100 mA
Circuit protection:
uilt-in overheating protection shuts down output when regulator IC gets too hot
Circuit complexity:
Very simple and easy to build
Circuit performance:
Very stable +5V output voltage, reliable operation
Availability of components:
Easy to get, uses only very common basic components
Design testing:
Based on datasheet example circuit, I have used this circuit succesfully as part of
many electronics projects
Applications:
Part of electronics devices, small laboratory power supply
Power supply voltage:
Unreglated DC 8-18V power supply
Power supply current:
Needed output current + 5 mA
Component costs:
Few dollars for the electronics components + the input transformer cost.
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CIRCUIT DIAGRAM:
Fig : Power Supply Circuit Diagram
This 5V dc acts as Vcc to the microcontroller. The excess voltage is dissipated as heat
via an Aluminum heat sink attached to the voltage regulator.
Bridge Rectifier :
A diode bridge is an arrangement of four diodes connected in a bridge
circuit as shown below, that provides the same polarity of output voltage for any polarity of
105
the input voltage. When used in its most common application, for conversion of alternating
current (AC) input into direct current (DC) output, it is known as a bridge rectifier. The
diagram describes a diode-bridge design known as a full-wave rectifier. This design can be
used to rectify single phase AC when no transformer center tap is available. A bridge
rectifier makes use of four diodes in a bridge arrangement to achieve full-wave rectification.
This is a widely used configuration, both with individual diodes wired as shown and with
single component bridges where the diode bridge is wired internally.
Typical Bridge Rectifier
For both positive and negative swings of the transformer, there is a Forward
path through the diode bridge. Both conduction paths cause Current to flow in the same
direction through the load resistor accomplishing full-wave rectification. While one set of
diodes is forward biased, the other set is reverse biased and effectively eliminated from the
circuit.
Current Flow in the Bridge Rectifier
Current in Bridge Rectifier for +ve half cycle
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Current in Bridge Rectifier for -ve half cycle
9.Software Components:
Data Types:U people have already come across the word “Data types” in C- Language. Here also
the functionality and the meaning of the word is same except a small change in the prefix of
their labels. Now we will discuss some of the widely used data types for embedded C-
programming.
Data Types Size in Bits Data Range/Usage
unsigned char 8-bit 0-255
signed char 8-bit -128 to +127
unsigned int 16-bit 0 to 65535
signed int 16-bit -32,768 to +32,767
sbit 1-bit SFR bit addressable only
bit 1-bit RAM bit addressable only
sfr 8-bit RAM addresses 80-FFH
only
Unsigned char:The unsigned char is an 8-bit data type that takes a value in the range of 0-255(00-
FFH). It is used in many situations, such as setting a counter value, where there is no need for
signed data we should use the unsigned char instead of the signed char. Remember that C
compilers use the signed char as the default if we do not put the key word.
Signed char:
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The signed char is an 8-bit data type that uses the most significant bit (D7 of D7-D0)
to represent the – or + values. As a result, we have only 7 bits for the magnitude of the signed
number, giving us values from -128 to +127. In situations where + and – are needed to
represent a given quantity such as temperature, the use of the signed char data type is a must.
Unsigned int:The unsigned int is a 16-bit data type that takes a value in the range of 0 to 65535
(0000-FFFFH).It is also used to set counter values of more than 256. We must use the int data
type unless we have to. Since registers and memory are in 8-bit chunks, the misuse of int
variables will result in a larger hex file. To overcome this we can use the unsigned char in
place of unsigned int.
Signed int: Signed int is a 16-bit data type that uses the most significant bit (D15 of D15-D0) to
represent the – or + value. As a result we have only 15 bits for the magnitude of the number
or values from -32,768 to +32,767.
Sbit (single bit): The sbit data type is widely used and designed specifically to access single bit
addressable registers. It allows access to the single bits of the SFR registers.
(II) I/O PROGRAMMING IN EMBEDDED “C”:In this topic we look at C- programming of the I/O ports and also both byte and bit
I/O programming.
Byte size I/O
As we know that ports P0-P3 are byte accessible, we use the P0-P3 labels as defined
in the header file.
Bit – addressable I/O programming
The I/O ports of P0-P3 are bit- addressable, so we can access a single bit without
disturbing the rest of the port. We use the sbit data type to access a single bit of P0-P3.the
format is Px^y where x is the port and y is the bit.
Accessing SFR addresses 80-FFH
Another way to access the SFR RAM space 80-FFH is to use the sfr data type. This is
shown in the below example. Both the bit and byte addresses for the P0-P3 ports are given in
the table. Notice in the given example that there is no #include<reg51.h> statement which
allows us to access any byte of the SFR RAM space 80-FFH.
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Single Bit Addresses of Ports
P0 Addr P1 Addr P2 Addr P3 Addr Ports
Bit
P0.0 80H P1.0 90H P2.0 A0H P3.0 B0H D0
P0.1 81H P1.1 91H P2.1 A1H P3.1 B1H D1
P0.2 82H P1.2 92H P2.2 A2H P3.2 B2H D2
P0.3 83H P1.3 93H P2.3 A3H P3.3 B3H D3
P0.4 84H P1.4 94H P2.4 A4H P3.4 B4H D4
P0.5 85H P1.5 95H P2.5 A5H P3.5 B5H D5
P0.6 86H P1.6 96H P2.6 A6H P3.6 B6H D6
P0.7 87H P1.7 97H P2.7 A7H P3.7 B7H D7
(III) DATA CONVERTION PROGRAMS IN EMBEDDED CMany micro-controllers have a real time clock (RTC) where the time and date are
kept even when the power is off. These time and date are often in packed BCD by RTC. To
display them they must be converted to ASCII. So, in this topic we are showing application
of logic and instructions in the conversion of BCD and ASCII.
ASCII numbers
On ASCII key boards, when the key “0” is activated, “0110000” (30h) is
provided to the system. Similarly 31h (0110001) is provided for the key “1”, and so on as
shown in the table
Packed BCD to ASCII conversion
The RTC provides the time of day (hour, minutes, seconds) and the date (year, month,
day) continuously, regardless of whether the power is ON or OFF. In the conversion
procedure the packed BCD is first converted to unpacked BCD. Then it is tagged with
0110000 (30h).
ASCII code for Digits 0-9
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Key ASCII (hex) Binary BCD (unpacked)
0 30 011 0000 0000 0000
1 31 011 0001 0000 0001
2 32 011 0010 0000 0010
3 33 011 0011 0000 0011
4 34 011 0100 0000 0100
5 35 011 0101 0000 0101
6 36 011 0110 0000 0110
7 37 011 0111 0000 0111
8 38 011 1000 0000 1000
9 39 011 1001 0000 1001
ASCII to packed BCD conversion
To convert ASCII to packed BCD it is first converted to unpacked and then combined
to make packed BCD. For example 4 and 7 on the keyboard give 34h and 37h respectively
the goal is to produce 47h or “0100 0111” which is packed BCD.
Key ASCII unpacked BCD packed BCD
4 34 00000100
7 37 00000111 01000111 or 47h
Checksum byte in ROM
To ensure the integrity of ROM contents, every system must perform the checksum
calculation. The process of checksum will detect any corruption of the contents of ROM. One
of the cause of the ROM corruption is current surge either when the system is turned on or
during operation. To ensure data integrity in ROM the checksum process uses, what is a
checksum byte. There is an extra byte that is tagged to the end of the series of data.
To calculate the checksum byte of a series of bytes of data, the following steps can be used
1) Add the bytes together and drop the carries.
2) Take the 2’s complement of the total sum. This is the checksum byte , which becomes
the last byte of the series
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Binary (hex) to decimal and ASCII conversion in embedded C:In C-language we use a function call “printf” which is standard IO library
function doing the conversions of data from binary to decimal, or vice versa. But here we are
using our own functions for conversions because it occupies much of memory.
One of the most commonly used is binary to decimal conversion. In devices such as
ADC chips the data is provided to the controller in binary. In order to display binary data we
need to convert it to decimal and then to ASCII. Since the hexadecimal format is a
convenient way of representing binary data we refer to binary data as hex. The binary data
00-FFH converted to decimal will give us 000 to 255.
One way to do this is to divide it by 10 and keep the remainder, for example
11111101 or FDH is 253 in decimal. The following is one version of the algorithm for
conversion of hex (binary) to decimal.
Quotient Remainder
FD/0A 19 3(low digit) LSD
19/0A 2 5(middle digit)
2(high digit) (MSD)
INTRODUCTION TO MATLAB
Matlab Introduction
MATLAB is a high performance language for technical computing .It integrates computation
visualization and programming in an easy to use environment
Mat lab stands for matrix laboratory. It was written originally to provide easy access to
matrix software developed by LINPACK (linear system package) and EISPACK (Eigen
system package) projects.
MATLAB is therefore built on a foundation of sophisticated matrix software in which the
basic element is matrix that does not require pre dimensioning
Typical uses of MATLAB
1. Math and computation
2. Algorithm development
3. Data acquisition
4. Data analysis ,exploration ands visualization
5. Scientific and engineering graphics
The main features of MATLAB
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1. Advance algorithm for high performance numerical computation ,especially in the
Field matrix algebra
2. A large collection of predefined mathematical functions and the ability to define one’s
own functions.
3. Two-and three dimensional graphics for plotting and displaying data
4. A complete online help system
5. Powerful, matrix or vector oriented high level programming language for individual
applications.
6. Toolboxes available for solving advanced problems in several application areas
Features and capabilities of MATLAB
The MATLAB System
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MATLAB
MATLABProgramming language
User written / Built in functions
Graphics2-D graphics3-D graphicsColor and lightingAnimation
ComputationLinear algebraSignal processingQuadratureEtc
External interfaceInterface with C and FORTRANPrograms
Tool boxesSignal processingImage processingControl systemsNeural NetworksCommunicationsRobust controlStatistics
The MATLAB system consists of five main parts:
Development Environment.
This is the set of tools and facilities that help you use MATLAB functions and files. Many of
these tools are graphical user interfaces. It includes the MATLAB desktop and Command
Window, a command history, an editor and debugger, and browsers for viewing help, the
workspace, files, and the search path.
The MATLAB Mathematical Function Library.
This is a vast collection of computational algorithms ranging from elementary functions, like
sum, sine, cosine, and complex arithmetic, to more sophisticated functions like matrix
inverse, matrix Eigen values, Bessel functions, and fast Fourier transforms.
The MATLAB Language.
This is a high-level matrix/array language with control flow statements, functions, data
structures, input/output, and object-oriented programming features. It allows both
"programming in the small" to rapidly create quick and dirty throw-away programs, and
"programming in the large" to create large and complex application programs.
Graphics.
MATLAB has extensive facilities for displaying vectors and matrices as graphs, as well as
annotating and printing these graphs. It includes high-level functions for two-dimensional and
three-dimensional data visualization, image processing, animation, and presentation graphics.
It also includes low-level functions that allow you to fully customize the appearance of
graphics as well as to build complete graphical user interfaces on your MATLAB
applications.
The MATLAB Application Program Interface (API).
This is a library that allows you to write C and Fortran programs that interact with MATLAB.
It includes facilities for calling routines from MATLAB (dynamic linking), calling MATLAB
as a computational engine, and for reading and writing MAT-files.
Starting MATLAB
On Windows platforms, start MATLAB by double-clicking the MATLAB shortcut icon on
your Windows desktop. On UNIX platforms, start MATLAB by typing mat lab at the
operating system prompt. You can customize MATLAB startup. For example, you can
change the directory in which MATLAB starts or automatically execute MATLAB
statements in a script file named startup.m
MATLAB Desktop
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When you start MATLAB, the MATLAB desktop appears, containing tools (graphical user
interfaces) for managing files, variables, and applications associated with MATLAB. The
following illustration shows the default desktop. You can customize the arrangement of tools
and documents to suit your needs. For more information about the desktop tools .
Implementations
1. Arithmetic operations
Entering Matrices
The best way for you to get started with MATLAB is to learn how to handle
matrices. Start MATLAB and follow along with each example.
You can enter matrices into MATLAB in several different ways:
• Enter an explicit list of elements.
• Load matrices from external data files.
• Generate matrices using built-in functions.
• Create matrices with your own functions in M-files.
Start by entering Dürer’s matrix as a list of its elements. You only have to follow a few basic
conventions:
• Separate the elements of a row with blanks or commas.
• Use a semicolon, to indicate the end of each row.
• Surround the entire list of elements with square brackets, [ ].
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To enter matrix, simply type in the Command Window
A = [16 3 2 13; 5 10 11 8; 9 6 7 12; 4 15 14 1]
MATLAB displays the matrix you just entered:
A =
16 3 2 13
5 10 11 8
9 6 7 12
4 15 14 1
This matrix matches the numbers in the engraving. Once you have entered the matrix, it is
automatically remembered in the MATLAB workspace. You can refer to it simply as A. Now
that you have A in the workspace,
sum, transpose, and diag
You are probably already aware that the special properties of a magic square have to do with
the various ways of summing its elements. If you take the sum along any row or column, or
along either of the two main diagonals, you will always get the same number. Let us verify
that using MATLAB.
The first statement to try is
sum(A)
MATLAB replies with
ans =34 34 34 34
When you do not specify an output variable, MATLAB uses the variable ans, short for
answer, to store the results of a calculation. You have computed a row vector containing the
sums of the columns of A. Sure enough, each of the columns has the same sum, the magic
sum, 34.
How about the row sums? MATLAB has a preference for working with the columns of a
matrix, so one way to get the row sums is to transpose the matrix, compute the column sums
of the transpose, and then transpose the result. For an additional way that avoids the double
transpose use the dimension argument for the sum function.
MATLAB has two transpose operators. The apostrophe operator (e.g., A') performs a
complex conjugate transposition. It flips a matrix about its main diagonal, and also changes
the sign of the imaginary component of any complex elements of the matrix. The apostrophe-
dot operator (e.g., A'.), transposes without affecting the sign of complex elements. For
matrices containing all real elements, the two operators return the same result. So
A'
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produces
ans =
16 5 9 4
3 10 6 15
2 11 7 14
13 8 12 1
and
sum(A')'
produces a column vector containing the row sums
ans =
34
34
34
34
The sum of the elements on the main diagonal is obtained with the sum and the diag
functions:
diag(A)
produces
ans =
16
10
7
1
and
sum(diag(A))
produces
ans =
34
The other diagonal, the so-called anti diagonal, is not so important Mathematically, so
MATLAB does not have a ready-made function for it. But a function originally intended for
use in graphics, fliplr, flips a matrix From left to right:
Sum (diag(fliplr(A)))
ans =
34
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You have verified that the matrix in Dürer’s engraving is indeed magic Square and, in the
process, have sampled a few MATLAB matrix operations.
Operators
Expressions use familiar arithmetic operators and precedence rules.
+ Addition
- Subtraction
* Multiplication
/ Division
\ Left division (described in “Matrices and Linear Algebra” in the
MATLAB documentation)
. ^ Power
' Complex conjugate transpose
( ) Specify evaluation order
Generating Matrices
MATLAB provides four functions that generate basic matrices.
zeros All zeros
ones All ones
rand Uniformly distributed random elements
randn Normally distributed random elements
Here are some examples:
Z = zeros(2,4)
Z =
0 0 0 0
0 0 0 0
F = 5*ones(3,3)
F =
5 5 5
5 5 5
5 5 5
N = fix(10*rand(1,10))
N =
9 2 6 4 8 7 4 0 8 4
R = randn(4,4)
R =
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0.6353 0.0860 -0.3210 -1.2316
-0.6014 -2.0046 1.2366 1.0556
0.5512 -0.4931 -0.6313 -0.1132
-1.0998 0.4620 -2.3252 0.3792
M-Files
You can create your own matrices using M-files, which are text files containing MATLAB
code. Use the MATLAB Editor or another text editor to create a file Containing the same
statements you would type at the MATLAB command Line. Save the file under a name that
ends in .m.
For example, create a file containing these five lines:
A = [...
16.0 3.0 2.0 13.0
5.0 10.0 11.0 8.0
9.0 6.0 7.0 12.0
4.0 15.0 14.0 1.0 ];
Store the file under the name magik.m. Then the statement magik reads the file and creates a
variable, A, containing our example matrix.
Graph Components
MATLAB displays graphs in a special window known as a figure. To create a graph, you
need to define a coordinate system. Therefore every graph is placed within axes, which are
contained by the figure. The actual visual representation of the data is achieved with graphics
objects like lines and surfaces. These objects are drawn within the coordinate system defined
by the axes, which MATLAB automatically creates specifically to accommodate the range of
the data. The actual data is stored as properties of the graphics objects.
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Plotting Tools
Plotting tools are attached to figures and create an environment for creating Graphs. These
tools enable you to do the following:
• Select from a wide variety of graph types
• Change the type of graph that represents a variable
• See and set the properties of graphics objects
• Annotate graphs with text, arrows, etc.
• Create and arrange subplots in the figure
• Drag and drop data into graphs
Display the plotting tools from the View menu or by clicking the plotting tools icon in the
figure toolbar, as shown in the following picture.
Editor/Debugger
Use the Editor/Debugger to create and debug M-files, which are programs you write to run
MATLAB functions. The Editor/Debugger provides a graphical user interface for text
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editing, as well as for M-file debugging. To create or edit an M-file use File > New or File >
Open, or use the edit function.
Results Both the algorithms were applied on different test cases and the following diagram
shows the result in speed and accuracy of both the algorithms
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. The speed and accuracy of both the algorithms
9.CIRCUIT DESCRIPTION:
we can implement a system in which a robot direction can be controlled wirelessly with
respect to the commands given by the user through PC using Zigbee technology
The required operating voltage for Microcontroller 89C51 is 5V. Hence the 5V D.C. power
supply is needed. This regulated 5V is generated by stepping down the voltage from 230V to
12V using step down transformer. Now the step downed a.c voltage is being rectified by the
Bridge Rectifier using 1N4007 diodes. The rectified a.c voltage is now filtered using a
‘Capacitor’ filter. Now the rectified, filtered D.C. voltage is fed to the Voltage Regulator.
This voltage regulator provides/allows us to have a Regulated constant Voltage which is of
+5V. The rectified; filtered and regulated voltage is again filtered for ripples using an
electrolytic capacitor 100μF. Now the output from this section is fed to 40th pin of 89c51
microcontroller to supply operating voltage. The microcontroller 89C51 with Pull up resistors
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at Port0 and crystal oscillator of 11.0592 MHz crystal in conjunction with couple of 30-33pf
capacitors is placed at 18th & 19th pins of 89c51 to make it work (execute) properly.
In this project, there are two sections (transmitter & receiver) as shown in the
block diagrams. The instructions such as Left, Right etc are processed and are given by the
person by operating PC. So based upon input of PC the following output will be seen i.e. left
or right. In Transmitter Section, the instructions are delivered to Zigbee transceiver from
microcontroller which is connected to the PC. This information is processed and is sent to
the receiver section via wireless.
In Receiver Section, the signals from the transmitter section are received by the
Zigbee transceiver and send to the controller as input. Controller will process this data and it
will control the Robot direction according to the instruction which is given at the transmitter
section. Then the Robot will move in that particular direction for the given instruction.
Similarly camera directions also controlled.
10.KEIL SOFTWARE:
Keil development tools for the 8051 Microcontroller Architecture support every level
of software developer from the professional applications engineer to the student just learning
about embedded software development.
The industry-standard Keil C Compilers, Macro Assemblers, Debuggers, Real-time
Kernels, Single-board Computers, and Emulators support all 8051 derivatives and help you
get your projects completed on schedule.
Simulation:
The µVision Simulator allows you to debug programs using only your PC using
simulation drivers provided by Keil and various third-party developers. A good simulation
environment, like µVision, does much more than simply simulate the instruction set of a
microcontroller — it simulates your entire target system including interrupts, startup code,
on-chip peripherals, external signals, and I/O.
This software is used for execution of microcontroller programs.
Keil development tools for the MC architecture support every level of software developer
from the professional applications engineer to the student just learning about embedded
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software development. The industry-standard keil C compilers, macro assemblers, debuggers,
real, time Kernels, Single-board computers and emulators support all microcontroller
deriveatives and help you to get more projects completed on schedule. The keil software
development tools are designed to solve the complex
Problems facing embedded software developers.
When starting a new project, simply select the microcontroller you the device
database and the µvision IDE sets all compiler, assembler, linker, and memory options for
you.
Numerous example programs are included to help you get started with the
most popular embedded avr devices.
The keil µ Vision debugger accurately simulates on-chip peripherals (PC,
CAN, UART, SPI,Interrupts,I/O ports, A/D converter, D/A converter and PWM modules)of
your avr device. Simulation helps you understand h/w configurations and avoids time wasted
on setup problems. Additionally,with simulation, you can write and test applications before
target h/w is available.
When you are ready to begin testing your s/w application with target h/w,use
the MON51, MON390, MONADI, or flash MON51 target monitors, the ISD51 In-System
Debugger, or the ULINK USB-JTAG adapter to download and test program code on your
target system.
11.SOURCE CODE:1. Click on the Keil uVision Icon on DeskTop
2. The following fig will appear
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3. Click on the Project menu from the title bar
4. Then Click on New Project
5. Save the Project by typing suitable project name with no extension in u r own folder sited in either C:\ or D:\
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6. Then Click on Save button above.
7. Select the component for u r project. i.e. Atmel……
8. Click on the + Symbol beside of Atmel
9. Select AT89C52 as shown below
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10. Then Click on “OK”
11. The Following fig will appear
12. Then Click either YES or NO………mostly “NO”
13. Now your project is ready to USE
14. Now double click on the Target1, you would get another option “Source group 1”
as shown in next page.
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15. Click on the file option from menu bar and select “new”
16. The next screen will be as shown in next page, and just maximize it by double
clicking on its blue boarder.
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17. Now start writing program in either in “C” or “ASM”
18. For a program written in Assembly, then save it with extension “. asm” and for
“C” based program save it with extension “ .C”
19. Now right click on Source group 1 and click on “Add files to Group Source”
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20. Now you will get another window, on which by default “C” files will appear.
21. Now select as per your file extension given while saving the file
22. Click only one time on option “ADD”
23. Now Press function key F7 to compile. Any error will appear if so happen.
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24. If the file contains no error, then press Control+F5 simultaneously.
25. The new window is as follows
26. Then Click “OK”
27. Now Click on the Peripherals from menu bar, and check your required port as
shown in fig below
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28. Drag the port a side and click in the program file.
29. Now keep Pressing function key “F11” slowly and observe.
30. You are running your program successfully
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12.CONCLUSION:
The project “PC CONTROLLED MILITARY ROBOT USING ZIGBEE” has been
successfully designed and tested.
It has been developed by integrating features of all the hardware components
used. Presence of every module has been reasoned out and placed carefully thus contributing
to the best working of the unit.
Secondly, using highly advanced IC’s and with the help of growing
technology the project has been successfully implemented.
13.FUTURE ENHANCEMENT:
This project is to design a robotic system for military applications using zigbee technology.
Here in this project robot is controlled through PC. And to implement a system in military
areas and also to monitor the locations by using cam which is connected to robot. And also
we can implement a system in which a robot direction can be controlled wirelessly with
respect to the commands given by the user through PC using Zigbee technology.
14.BIBLIOGRAPHY:
The 8051 Micro controller and Embedded Systems -Muhammad Ali Mazidi Janice Gillispie MazidiThe 8051 Micro controller Architecture, Programming & Applications -Kenneth J.AyalaFundamentals Of Micro processors and Micro computers -B.RamMicro processor Architecture, Programming & Applications -Ramesh S.GaonkarElectronic Components -D.V.PrasadWireless Communications - Theodore S. RappaportReferences on the Web:
www.national.comwww.atmel.comwww.microsoftsearch.comwww.geocities.com
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