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BTS BUS TRACKING USING GPS & GSM SYSTEM INTRODUCTION This project is based on VTU syllabus. The proposed system is based on ATMEL 89C52 µcontroller, which is in our syllabus. For doing this project we use some of the software like Embedded C for programming the application software to the microcontroller. Protel schematic software is used for designing the circuit diagram for this project. Express PCB software is used for designing the PCB for this project. (Since PCB making is a big process and involves lot of machineries, which are expensive. So we are going to outsource this to the manufacture.)

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Page 1: Bus Tracking Using Gps & Gsm System

BTS BUS TRACKING USING GPS & GSM SYSTEM

INTRODUCTION

This project is based on VTU syllabus. The proposed system is based on

ATMEL 89C52 µcontroller, which is in our syllabus.

For doing this project we use some of the software like

Embedded C for programming the application software to the

microcontroller.

Protel schematic software is used for designing the circuit diagram for

this project.

Express PCB software is used for designing the PCB for this project.

(Since PCB making is a big process and involves lot of machineries, which

are expensive. So we are going to outsource this to the manufacture.)

Page 2: Bus Tracking Using Gps & Gsm System

ABSTRACT:

The main aim of this project is to map the vehicles and find out the speed of

the vehicles; this system uses GPS receiver/transmitter, GSM

receiver/transmitter with a micro controller.

Imagine the vehicle has left Bangalore at 6 o clock in the morning. If the

officer in charge for that vehicle wants to know where this bus is, he will send

an SMS to that particular bus number. The SMS, which has sent, by the officer

will reach the vehicle, which is traveling and there it will compare the

password and the command. If every thing matches then it will perform the

request required by the officer. In this way we can easily map the vehicle

position or speed of the vehicle from the place where they are sitting.

In our project the PCB is designed by using Express PCB & the circuit is

designed by using Proteus software.

WORKING PRINCIPLE:

The project consists of GPS receiver and GSM modem with a micro

controller. The whole system is attached to the vehicle. In the other end (main

vehicle station) one GSM mobile phone is attached to the computer with VB

application. So the GPS system will send the longitudinal and altitude values

corresponding to the position of vehicle to GSM Modem.

Imagine the bus has left Bangalore at 6 o clock in the morning. If the officer

in charge for that vehicle wants to know where the vehicle is, he will come to

the computer and click on the vehicle number on the VB program .The VB

program will send an SMS to the vehicle number.

The SMS sent would come through the GSM service provider and then

reach the vehicle, which is traveling, because the vehicle has a GSM device

Page 3: Bus Tracking Using Gps & Gsm System

with sim card. This GSM modem will receive the SMS and send to the

microcontroller in the vehicle. The microcontroller will receive this SMS and

compare the password and the command. If every thing matches then it will

perform the request required by the office.

A place name is assigned for each longitude & latitude. The GSM receiver

in the vehicle office receives these data & gives to the PC through serial port.

The VB program in the PC checks this data with its database & displays the

details of the vehicle on the screen. The device is password controlled i.e.

person who knows the device password only able to operate.

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BLOCK DIAGRAM

Transmitter

GPS/GSMSELECTOR

GPSReceiver

GSMMODEM RS232

Micro Controller (AT89S52)

Power Supply

Trans former

Rectifier Filter

Regulator(7805)

Memory

RTC

RTC OSC

Battery Backup

LCD (Display)

LCD Glass

LCD Driver

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COMPONENTS USED:

Power Supply 5v DC - 7805

Micro controller - AT89S52-Atm(www.Atmel.Com)

External EEPROM memory - AT24C02/4/8/16/32A

LCD - (Liquid crystal display) 2 x16

Real Time Clock (RTC) - DS1307 (www.Dallas.Com)

Serial Communication - MAX 232

Buzzer - Freq-1 to 18 kHz (5v-12Vdc)

GSM modem (900/1800 MHz)

GPS receiver (with licence).

SOFTWARE USED:

Embedded C.

Visual basics (VB)

COMPONENT APPLICATIONS:

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Power supply:

The microcontroller and other devices get power supply from AC to Dc

adapter through voltage regulator. The adapter output voltage will be 12V DC

non-regulated. The 7805 voltage regulators are used to convert 12 V to 5VDC.

Vital role of power supply in ‘BTS BUS TRACKING USING GPS & GSM SYSTEM’. The adapter output voltage will be 12V DC non-regulated. The 7805/7812 voltage regulators are used to convert 12 V to 5V/12V DC.

Microcontroller:

The AT89C52 is a low-power, high-performance CMOS 8-bit

microcontroller with 8K bytes of in-system programmable Flash memory. The

device is manufactured using Atmel’s high-density nonvolatile memory

technology and is compatible with the industry- standard 80C51 instruction set

and pin out.

Features:

8K Bytes of In-System Programmable (ISP) Flash Memory

Endurance: 1000 Write/Erase Cycles

4.0V to 5.5V Operating Range

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Full Duplex UART Serial Channel

Fully Static Operation: 0 Hz to 33 MHz

DC OutputAC Power

AC/DC Adapter

Regulator (7805)

Filter

Page 7: Bus Tracking Using Gps & Gsm System

Vital role of Micro controller-AT89C52 in ‘Vehicle position tracking

using GPS AND GSM receiver with licence’ The microcontroller will

receive the SMS, which has sent from the office and compare the password

and the command. If every thing matches then it will perform the request

required by the office.

Memory:

These memory devices are used to store the data for off line process. The

AT24C02A / 04A/ 08A/ 32/64 provides 2048/4096/8192/32,768/65,536 bits of

serial electrically erasable and programmable read only memory (EEPROM)

organized as 56/512/1024/4096/8192 words of 8 bits each. The device is

optimized for use in many industrial and commercial applications where low

power and low voltage operation are essential. The AT24C02A/04A/08A is

available in space saving 8-pin PDIP.

Features

Internally Organized 256 x 8 (2K), 512 x 8 (4K) or 1024 x 8 (8K)

2-Wire Serial Interface (I2C protocol)

High Reliability

– Endurance: 1 Million Write Cycles

– Data Retention: 100 Years

– ESD Protection: >3000V

Vital role of External EEPROM memory in ‘BTS BUS TRACKING USING GPS & GSM SYSTEM’ is used to store the longitudinal and latitudinal values.

RS 232 CONVERTER (MAX 232N) Serial Port:

This is the device, which is used to convert TTL/RS232 vice versa.

RS-232Protocol

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RS-232 was created for one purpose, to interface between Data Terminal

Equipment (DTE) and Data Communications Equipment (DCE) employing

serial binary data interchange. So as stated the DTE is the terminal or computer

and the DCE is the modem or other communications device.

RS-232 pin-outs for IBM compatible computers are shown below.  There

are two configurations that are typically used: one for a 9-pin connector and

the other for a 25-pin connector.

Real Time Clock (RTC – DS1307):

This is used to maintain the current time in off line processing. The DS1307

Serial Real-Time Clock is a low power; full binary-coded decimal (BCD)

clock/calendar plus 56 bytes of NV SRAM. Address and data are transferred

serially via a 2-wire, bi-directional bus. The clock/calendar provides seconds,

minutes, hours, day, date, month, and year information. The end of the month

date is automatically adjusted for months with fewer than 31 days, including

corrections for leap year. The clock operates in either the 24-hour or 12-hour

format with AM/PM indicator. The DS1307 has a built-in power sense circuit

that detects power failures and automatically switches to the battery supply.

Features

It uses I2C protocol

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_ Real-time clock (RTC) counts seconds, minutes, hours, date of the month,

month, and day of the week, and year with leap-year compensation valid up to

2100.

_Two-wire serial interface Consumes less than 500nA in battery backup

mode with oscillator running

Vital role of RTC in ‘BTS BUS TRACKING USING GPS & GSM

SYSTEM’ is used to get the current time.

LCD:

LCDs can add a lot to your application in terms of providing an useful

interface for the user, debugging an application or just giving it a

"professional" look. The most common type of LCD controller is the Hitatchi

44780, which provides a relatively simple interface between a processor and an

LCD. Inexperienced designers do often not attempt using this interface and

programmers because it is difficult to find good documentation on the

interface, initializing the interface can be a problem and the displays

themselves are expensive.

LCD has single line display, Two-line display, four line display. Every line

has 16 characters.

Vital role of LCD in ‘BUS TRACKING USING GPS & GSM SYSTEM‘ is

used to display the corresponding action in written form.

GSM modem (900/1800 MHz):

Semens GSM/GPRS Smart Modem is a multi-functional, ready to use,

rugged unit that can be embedded or plugged into any application. The Smart

Modem can be controlled and customized to various levels by using the

standard AT commands. The modem is fully type-approved, it can speed up

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the operational time with full range of Voice, Data, Fax and Short Messages

(Point to Point and Cell Broadcast), the modem also supports GPRS (Class 2*)

for spontaneous data transfer.

Description of the interfaces

The modem comprises several interfaces:

- LED Function including operating Status

- External antenna (via SMA)

- Serial and control link

- Power Supply (Via 2 pin Phoenix tm contact)

- SIM card holder

LED Status Indicator

The LED will indicate different status of the modem:

- OFF Modem Switched off

- ON Modem is connecting to the network

- Flashing Slowly Modem is in idle mode

- Flashing rapidly Modem is in transmission/communication (GSM

only)

Vital role of GSM MODEM in ‘BUS TRACKING USING GPS & GSM

SYSTEM’ is used to transmit and receive the SMS.

GPS RECEIVER:

ITRAX02 receiver produces and interprets messages in accordance with the

NMEA (National Marine Electronics association) standard (its with licence).

The fully autonomous receiver provides high position and speed accuracy

performances as well as high sensitivity and tracking capabilities in urban

conditions. The solutions enable small form factor devices. The deliver major

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advancements in GPS performances, accuracy, integration, computing power

and flexibility. They are designed to simplify the embedded system integration

process. The NMEA commands used for controlling the basic ITRAX

operations. The accuracy of the receiver is 50 to 100 meters.

APPLICATIONS

- Car navigation

- Fleet management/tracking

- Palmtop, Laptop, PDA, and Handheld

- Location Based Services enabled devices

Vital role of GPS RECEIVER in ‘BUS TRACKING USING GPS & GSM

SYSTEM’ is used for finding the longitude and latitude values.

COMPONENT DESCRIPTION:

Micro controller-AT89C52:

The AT89C52 is a low-power, high-performance CMOS 8-bit

microcontroller with 8K bytes of in-system programmable Flash memory. The

device is manufactured using Atmel’s high-density nonvolatile memory

technology and is compatible with the industry- standard 80C51 instruction set

and pin out.

Features:

8K Bytes of In-System Programmable (ISP) Flash Memory

Endurance: 1000 Write/Erase Cycles

4.0V to 5.5V Operating Range

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Full Duplex UART Serial Channel

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Fully Static Operation: 0 Hz to 33 MHz

The AT89C52 is a low-power, high-performance CMOS 8-bit

microcontroller with 8K bytes of in-system programmable Flash memory. The

device is manufactured using Atmel’s high-density nonvolatile memory

technology and is compatible with the industry-standard 80C51 instruction set

and pinout. The on-chip Flash allows the program memory to be

reprogrammed in-system or by a conventional nonvolatile memory

programmer. By combining a versatile 8-bit CPU with in-system

programmable Flash on a monolithic chip, the Atmel AT89C52 is a powerful

microcontroller which provides a highly-flexible and cost-effective solution to

many embedded control applications. The AT89C52 provides the following

standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines,

Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector

two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and

clock circuitry. In addition, the AT89C52 is designed with static logic for

operation down to zero frequency and supports two software selectable power

saving modes. The Idle Mode stops the CPU while allowing the RAM,

timer/counters, serial port, and interrupt system to continue functioning. The

Power-down mode saves the RAM contents but freezes the oscillator, disabling

all other chip functions until the next interrupt or hardware reset.

RS 232 CONVERTER (MAX 232N) Serial Port:

This is the device, which is used to convert TTL/RS232 vice versa.

RS-232Protocol

In telecommunications, RS-232 is a standard for serial binary data

interconnection between a DTE (Data terminal equipment) and a DCE (Data

Circuit-terminating Equipment). It is commonly used in computer serial ports.

The RS-232 standard defines the voltage levels that correspond to logical one

and logical zero levels. Valid signals are plus or minus 3 to 15 volts. The range

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near zero volts is not a valid RS-232 level; logic one is defined as a negative

voltage, the signal condition is called marking, and has the functional

significance of OFF.

RS-232 was created for one purpose, to interface between Data Terminal

Equipment (DTE) and Data Communications Equipment (DCE) employing

serial binary data interchange. So as stated the DTE is the terminal or computer

and the DCE is the modem or other communications device.

RS-232 pin-outs for IBM compatible computers are shown below.  There

are two configurations that are typically used: one for a 9-pin connector and

the other for a 25-pin connector.

LCD:

LCDs can add a lot to your application in terms of providing an useful

interface for the user, debugging an application or just giving it a

"professional" look. The most common type of LCD controller is the Hitatchi

44780, which provides a relatively simple interface between a processor and an

LCD. Inexperienced designers do often not attempt using this interface and

programmers because it is difficult to find good documentation on the

interface, initializing the interface can be a problem and the displays

themselves are expensive.

Page 14: Bus Tracking Using Gps & Gsm System

LCD has single line display, Two-line display, four line display. Every line

has 16 characters.

EEPROM 24C04:

Features

• Low-voltage and Standard-voltage Operation

– 2.7 (VCC = 2.7V to 5.5V)

– 1.8 (VCC = 1.8V to 5.5V)

• Internally Organized 128 x 8 (1K), 256 x 8 (2K), 512 x 8 (4K),

1024 x 8 (8K) or 2048 x 8 (16K)

• 2-wire Serial Interface

• Schmitt Trigger, Filtered Inputs for Noise Suppression

• Bi-directional Data Transfer Protocol

• 100 kHz (1.8V, 2.5V, 2.7V) and 400 kHz (5V) Compatibility

• Write Protect Pin for Hardware Data Protection

• 8-byte Page (1K, 2K), 16-byte Page (4K, 8K, 16K) Write Modes

• Partial Page Writes are Allowed

• Self-timed Write Cycle (10 ms max)

• High-reliability

– Endurance: 1 Million Write Cycles

– Data Retention: 100 Years

• Automotive Grade, Extended Temperature and Lead-Free Devices

Available

• 8-lead PDIP, 8-lead JEDEC SOIC, 8-lead MAP, 5-lead SOT23,

8-lead TSSOP and 8-ball dBGA2™ Packages

Description:

The AT24C01A/02/04/08/16 provides 1024/2048/4096/8192/16384 bits of

serial electrically erasable and programmable read-only memory (EEPROM)

organized as128/256/512/1024/2048 words of 8 bits each. The device is

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optimized for use in many industrial and commercial applications where low-

power and low-voltage operation are essential. The AT24C01A/02/04/08/16 is

available in space-saving 8-lead PDIP, 8-lead JEDEC SOIC, 8-lead MAP, 5-

lead SOT23 (AT24C01A/AT24C02/AT24C04), 8-lead TSSOP and 8-ball

dBGA2 packages and is accessed via a 2-wire serial interface. In addition, the

entire family is available in 2.7V (2.7V to 5.5V) and 1.8V (1.8V to 5.5V)

versions.

PIN Diagram:

GSM modem (900/1800 MHz):

History of GSM

During the early 1980s, analog cellular telephone systems were

experiencing rapid growth in Europe, particularly in Scandinavia and the

United Kingdom, but also in France and Germany. Each country developed its

own system, which was incompatible with everyone else's in equipment and

operation. This was an undesirable situation, because not only was the mobile

equipment limited to operation within national boundaries, which in a unified

Europe were increasingly unimportant, but there was also a very limited

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market for each type of equipment, so economies of scale and the subsequent

savings could not be realized.

The Europeans realized this early on, and in 1982 the Conference of

European Posts and Telegraphs (CEPT) formed a study group called the

Groupe Spécial Mobile (GSM) to study and develop a pan-European public

land mobile system. The proposed system had to meet certain criteria:

Good subjective speech quality

Low terminal and service cost

Support for international roaming

Ability to support handheld terminals

Support for range of new services and facilities

Spectral efficiency

ISDN compatibility

In 1989, GSM responsibility was transferred to the European

Telecommunication Standards Institute (ETSI), and phase I of the GSM

specifications were published in 1990. Commercial service was started in mid-

1991, and by 1993 there were 36 GSM networks in 22 countries. Although

standardized in Europe, GSM is not only a European standard. Over 200 GSM

networks (including DCS1800 and PCS1900) are operational in 110 countries

around the world. In the beginning of 1994, there were 1.3 million subscribers

worldwide, which had grown to more than 55 million by October 1997. With

North America making a delayed entry into the GSM field with a derivative of

GSM called PCS1900, GSM systems exist on every continent, and the

acronym GSM now aptly stands for Global System for Mobile

communications.

The developers of GSM chose an unproven (at the time) digital system, as

opposed to the then-standard analog cellular systems like AMPS in the United

States and TACS in the United Kingdom. They had faith that advancements in

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compression algorithms and digital signal processors would allow the

fulfillment of the original criteria and the continual improvement of the system

in terms of quality and cost. The over 8000 pages of GSM recommendations

try to allow flexibility and competitive innovation among suppliers, but

provide enough standardization to guarantee proper interworking between the

components of the system. This is done by providing functional and interface

descriptions for each of the functional entities defined in the system.

Services provided by GSM

From the beginning, the planners of GSM wanted ISDN compatibility in

terms of the services offered and the control signalling used. However, radio

transmission limitations, in terms of bandwidth and cost, do not allow the

standard ISDN B-channel bit rate of 64 kbps to be practically achieved.

Using the ITU-T definitions, telecommunication services can be divided

into bearer services, teleservices, and supplementary services. The most basic

teleservice supported by GSM is telephony. As with all other communications,

speech is digitally encoded and transmitted through the GSM network as a

digital stream. There is also an emergency service, where the nearest

emergency-service provider is notified by dialing three digits (similar to 911).

A variety of data services is offered. GSM users can send and receive data,

at rates up to 9600 bps, to users on POTS (Plain Old Telephone Service),

ISDN, Packet Switched Public Data Networks, and Circuit Switched Public

Data Networks using a variety of access methods and protocols, such as X.25

or X.32. Since GSM is a digital network, a modem is not required between the

user and GSM network, although an audio modem is required inside the GSM

network to interwork with POTS.

Other data services include Group 3 facsimile, as described in ITU-T

recommendation T.30, which is supported by use of an appropriate fax

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adaptor. A unique feature of GSM, not found in older analog systems, is the

Short Message Service (SMS). SMS is a bidirectional service for short

alphanumeric (up to 160 bytes) messages. Messages are transported in a store-

and-forward fashion. For point-to-point SMS, a message can be sent to another

subscriber to the service, and an acknowledgement of receipt is provided to the

sender. SMS can also be used in a cell-broadcast mode, for sending messages

such as traffic updates or news updates. Messages can also be stored in the

SIM card for later retrieval .

Supplementary services are provided on top of teleservices or bearer

services. In the current (Phase I) specifications, they include several forms of

call forward (such as call forwarding when the mobile subscriber is

unreachable by the network), and call barring of outgoing or incoming calls,

for example when roaming in another country. Many additional supplementary

services will be provided in the Phase 2 specifications, such as caller

identification, call waiting, multi-party conversations.

AT COMMANDS USED:

SIM Insertion, SIM Removal

SIM card Insertion and Removal procedures are supported. There are

software functions relying on positive reading of the hardware SIM detect pin.

This pin state (open/closed) ispermanently monitored.When the SIM detect pin

indicates that a card is present in the SIM connector, the product tries to set up

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a logical SIM session. The logical SIM session will be set up or not depending

on whether the detected card is a SIM Card or not. The AT+CPIN? command

delivers the following responses:

If the SIM detect pin indicates “absent”, the response to AT+CPIN? is

“+CME ERROR 10” (SIM not inserted).

If the SIM detect pin indicates “present”, and the inserted Card is a SIM

Card, the response to AT+CPIN? is “+CPIN: xxx” depending on SIM PIN

state.

If the SIM detect pin indicates “present”, and the inserted Card is not a SIM

Card, the response to AT+CPIN? is CME ERROR 10.

These last two states are not given immediately due to background

initialization. Between the hardware SIM detect pin indicating “present” and

the previous results the AT+CPIN? sends “+CME ERROR: 515” (Please wait,

init in progress).

When the SIM detect pin indicates card absence, and if a SIM Card was

previously inserted, an IMSI detach procedure is performed, all user data is

removed from the product (Phonebooks, SMS etc.). The product then switches

to emergency mode.

Call Control commands

Dial command D

Description:

The ATD command is used to set a voice, data or fax call. As per GSM

02.30, the dial command also controls supplementary services. For a data or a

fax call, the application sends the following ASCII string to the product (the

bearer must be previously selected with the +CBST command):

ATD<nb> where <nb> is the destination phone number.

For a voice call, the application sends the following ASCII string to the

product: (the bearer may be selected previously, if not a default bearer is used).

Page 20: Bus Tracking Using Gps & Gsm System

ATD<nb>; where <nb> is the destination phone number.

Please note that for an international number, the local international prefix

does not need to be set (usually 00) but does need to be replaced by the ‘+’

character.

Example: to set up a voice call to Wavecom offices from another country,

the AT command

is: “ATD+33146290800;”

Note that some countries may have specific numbering rules for their GSM

handset numbering.

The response to the ATD command is one of the following:

Verbose result code Numeric code

Description

with ATV0 set

OK 0 ifthe call succeeds,

for voice call only

CONNECT <speed> 10,11,12, ifthe call succeeds,

for data calls only,

13,14,15 <speed> takes the

value negotiated

by the product.

BUSY 7 If the called party I

is Already in

communication

NO ANSWER 8 If no hang up is

detected

after a fixed

Page 21: Bus Tracking Using Gps & Gsm System

network

time-out

NO CARRIER 3 Call setup failed or

remote user

release

Echo E

Description:

This command is used to determine whether or not the modem echoes

characters received by an external application (DTE).

Syntax:

Command Syntax: ATE

COMMAND POSSIBLE

RESPONSES

ATE0 OK

Note: Characters are not echoed Note:

Done

ATE1 OK

Note: Characters are echoed Note:

Done

55

Select message service +CSMS

Description:

The supported services are originated (SMS-MO) and terminated short

message (SMSMT) + Cell Broadcast Message (SMS-CB) services.

Syntax:

Command Syntax: AT+CSMS=<service>

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COMMAND POSSIBLE

RESPONSES

AT+CSMS=0 +CSMS: 1,1,1

OK

AT+CSMS=1 +CSMS: 1,1,1

Preferred Message Format +CMGF

Description:

The message formats supported are text mode and PDU mode.In PDU

mode, a complete SMS Message including all header information is given as a

binary string (in hexadecimal format). Therefore, only the following set of

characters is

allowed: {‘0’,’1’,’2’,’3’,’4’,’5’,’6’,’7’,’8’,’9’, ‘A’, ‘B’,’C’,’D’,’E’,’F’}.

Each pair or characters is converted to a byte (e.g.: ‘41’ is converted to the

ASCII character ‘A’, whose ASCII code is0x41 or 65). In Text mode, all

commands and responses are in ASCII characters.

Syntax:

Command Syntax: AT+CMGF

COMMAND POSSIBLE

RESPONSES

AT+CMGF=0 OK

Set PDU mode

AT+CMGF=1 OK

Set TEXT mode

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New message indication +CNMI

Description:

This command selects the procedure for message reception from the

network.

Syntax:

Command Syntax: AT+CNMI=<mode>,<mt>,<bm>,<ds>,<bfr>

COMMAND POSSIBLE

RESPONSES

AT+CNMI=2,1,0,0,0 OK

AT+CMTI : “SM”,1

Note:message

received

AT+CNMI=2,2,0,0,0 OK

+CMT“123456”,”98/1

0/01,

12:3000+00”,129,4,32

,240,

“15379”,129,5<CR>

<LF>

Read message +CMGR

Description:

This command allows the application to read stored messages.

Syntax:

Command Syntax: AT+CMGR=<index>

A message read with status “REC UNREAD” will be updated in memory

with the status “REC READ”.

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COMMAND POSSIBLE

RESPONSES

AT+CMTI: “SM”,1

AT+CMGR=1 +CMGR: “REC

UNREAD”,”0146290

800”,

”98/10/01,18:22

:11+00”,<CR><LF>

ABCdefGHI

OK

Note: read the message

Send message +CMGS

Description:

The <address> field is the address of the terminal to which the message is

sent. To send he message, simply type, <ctrl-Z> character (ASCII 26). The text

can contain all existing characters except <ctrl-Z> and <ESC> (ASCII 27).

This command can be aborted using the <ESC> character when entering

text.

In PDU mode, only hexadecimal characters are used (‘0’…’9’,’A’…’F’).

Syntax:

Command syntax in text mode:

AT+CMGS= <da> [ ,<toda> ] <CR>

text is entered <ctrl-Z / ESC >

COMMAND POSSIBLE

RESPONSES

AT+CMGS=”+33146290800”<CR> +CMGS: <mr>

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Please call me soon, Fred. <ctrl-Z> OK

Note: Send a message in text mode Note: Successful

transmission

The message reference, <mr>, which is returned to the application is

allocated by the product. This number begins with 0 and is incremented by one

for each outgoing message(successful and failure cases); it is cyclic on one

byte (0 follows 255).

Global Positioning System (GPS):

The Global Positioning System (GPS), is the only fully-functional satellite

navigation system. More than two dozen GPS satellites orbit the Earth,

transmitting radio signals which allow GPS receivers to determine their

location, speed and direction. GPS has become indispensable for navigation

around the world and an important tool for map-making and synchronization of

telecommunications networks.

How it works - simple introduction:

A GPS receiver calculates its position by measuring the distance between

itself and three or more GPS satellites. Measuring the time delay between

transmission and reception of each GPS radio signal gives the distance to each

satellite, since the signal travels at a known speed. The signals also carry

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information about the satellites' location. By determining the position of, and

distance to, at least three satellites, the receiver can compute its location using

trilateration.Receivers do not have perfectly accurate clocks, and must track

one extra satellite to correct their clock error.

Technical description

Satellites and Ground Control:

The GPS design calls for 24 satellites to be distributed equally among six

circular orbital planes with 55° declination (tilt relative to the equator) and

separated by 60° right ascension (angle along the equator). Orbiting at an

altitude of 10,988 nautical miles (approximately 20,200 kilometers or 12,600

statute miles), each satellite passes over the same location on Earth twice a

day. The orbits are arranged so that at least four satellites are always within

line of sight from almost anywhere on Earth.

The satellites also broadcast two forms of clock information, the Coarse /

Acquisition code, or C/A which is freely available to the public, and the

restricted Precise code, or P-code, usually reserved for military applications.

The C/A code is a 1,023 bit long pseudo-random code broadcast at 1.023 MHz,

repeating every millisecond. Each satellite sends a distinct C/A code, which

allows it to be uniquely identified. The P-code is a similar code broadcast at

10.23 MHz, but it repeats only once a week. In normal operation, the so-called

"anti-spoofing mode", the P code is first encrypted into the Y-code, or P(Y),

which can only be decrypted by units with a valid decryption key. Frequencies

used by GPS include:

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L1 (1575.42 MHz) - Mix of Navigation Message, coarse-acquisition

(C/A) code and encrypted precision P(Y) code.

L2 (1227.60 MHz) - P(Y) code, and a second C/A code on the Block II-

R and newer satellites.

L3 (1381.05 MHz) - Used by the Defense Support Program to signal

detection of missile launches, nuclear detonations, and other high-

energy infrared events.

L4 (1841.40 MHz) - Being studied for additional ionospheric

correction.

L5 (1176.45 MHz) - Proposed for use as a civilian safety-of-life (SoL)

signal. This frequency falls into an internationally protected range for

aeronautical navigation, promising little or no interference under all

circumstances. The first Block IIF satellite that would provide this

signal is set to be launched in 2008.

Receivers:

In general, GPS receivers are composed of an antenna, tuned to the

frequencies transmitted by the satellites, receiver-processors, and a highly-

stable clock (often a crystal oscillator). They may also include a display for

providing location and speed information to the user. A receiver is often

described by its number of channels: this signifies how many satellites it can

monitor simultaneously. Originally limited to four or five, this has

progressively increased over the years such that, as of 2006, receivers typically

have between twelve and twenty channels.

Many GPS receivers can relay position data to a PC or other device using

the NMEA 0183 protocol. NMEA 2000 is a newer and less widely adopted

protocol. Both are proprietary and controlled by the US-based National Marine

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Electronics Association. References to the NMEA protocols have been

compiled from public records, allowing open source tools like gpsd to read the

protocol without violating intellectual property laws. Other proprietary

protocols exist as well, such as the SiRF protocol. Receivers can interface with

other devices using methods including a serial connection, USB or

Bluetooth.

General NMEA commands:

START – Start Navigation

Commands iTrax to start navigation. The command has no effect if called

while iTrax is already navigating. After the start command has been given, it

takes some time from iTrax to acquire satellites, acquire required navigation

data from the signal and calculate a first fix.

$PFST,START,<startmode>

Examples:

$PFST,START<CR><LF>

Starts navigation using the fastest possible start mode.

$PFST,START,2<CR><LF>

Starts navigation using warm start mode if possible.

STOP – Stop Navigation:

Commands iTrax to stop navigation and enter idle state. At idle state iTrax

receiverdoesn’t navigate but still accepts commands. Idle state consumes less

power than navigation state, but remarkably more than in the power-down

mode. This command also stores the “LastKnownGood” fix, ephemeris and

almanac data acquired during

navigation to flash memory.

$PFST,STOP,<1|0>

NMEA MESSAGES:

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This is one of the NMEA messages.

GGA – Global Positioning System Fix Data

Time, position and fix related data for a GPS receiver.

$GPGGA,hhmmss.dd,xxmm.dddd,<N|S>,yyymm.dddd,<E|W>,v,

ss,d.d,h.h

,M,g.g,M,a.a,xxxx*hh<CR><LF>

Example:

$GPGGA,111200.02,6016.3092,N,02458.3841,E,1,09,0.8,30.6,M,18.1

,M,,*5D

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APPLICATION OF THIS PROJECT:

For identification of person, vehicles etc

For finding the speed of the vehicles