Embedded Microcontrollers LED Based Program Design

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Embedded Microcontrollers

LED Based Program Design

Author: Jordan Lee Mauro-Buhagiar

Student ID: P132135

Lecturer: Caerwyn Ash

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Table of Contents Summary ................................................................................................................................................. 4

Chapter I - Introduction ....................................................................................................................... 5

1.1 Introduction to Microcontrollers ....................................................................................................... 5

Figure 1.10 – First ever microcontroller ................................................................................................. 5

Figure 1.12 – Different types of microcontrollers used in a range of devices .................................... 5

Chapter II - Literature Review ............................................................................................................ 7

2.1. Microcontroller - Design & Architecture ......................................................................................... 7

Figure 2.10 – Basic microcontroller structure & operation .................................................................... 7

2.2. Microcontroller and microprocessor Dissimilarities ........................................................................ 8

Figure 2.21 – Microprocessor and microcontroller disparity .................................................................. 8

2.3. Central Processing Unit (CPU) ........................................................................................................ 9

2.31. Memory .................................................................................................................................... 10

2.32. Input and Output (I/O) ......................................................................................................... 10

2.4. Microcontroller Organisation ......................................................................................................... 11

2.5. Microcontroller - Software program .............................................................................................. 12

2.6. Research of Program Development ............................................................................................... 13

2.61. Registers ................................................................................................................................... 13

Figure 2.610 – Map Register................................................................................................................. 13

Figure 2.611 – Binary values determine I/O ports ............................................................................ 14

Chapter III – Research Methodology ................................................................................................ 15

3.1. Design and Development of the circuit and software .................................................................... 15

Figure 3.11 – Circuit Block Diagram.................................................................................................... 15

Figure 3.12 – Program development block diagram......................................................................... 15

3.11 Circuit requirements ...................................................................................................................... 16

Figure 3.13 – Circuit diagram ............................................................................................................... 16

Figure 3.14 - Program test1 .............................................................................................................. 17

Figure 3.15 – LED flashing, on & off .............................................................................................. 18

3.2. Timer0 Module & Set-up ............................................................................................................... 19

Figure 3.21 - TMR0 Block Diagram ..................................................................................................... 19

3.3. Prescaler Set-up ............................................................................................................................. 20

Figure 3.31 – Option Register functionalities & Prescaler rate ............................................................ 20

Test 2 – Worked example 1 on time delays .......................................................................................... 21

Figure 3.32 – 1 Second time delay subroutine ...................................................................................... 21

Figure 3.33 – 1 second delay illustration .......................................................................................... 22

Test 3, worked example 2 on time delay (6seconds) ............................................................................ 23

Figure 3.34 – Time delay increased to 6 seconds ................................................................................. 23

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Test 4 – Figure 3.35 – Four minute delay ............................................................................................. 23

Figure 3.36 – Circuit test when calling 4 minute delay ..................................................................... 24

Test 5 - Figure 3.37 – 1 hour delay ....................................................................................................... 24

Test 6 – Testing both delays together ................................................................................................... 24

Figure 3.38 – Program executing with an LED response ..................................................................... 25

Figure 3.39 – Rearranged program ................................................................................................... 25

Figure 3.310 - Test example .......................................................................................................... 26

Figure 3.311 – 6 Hour delay program with 4 minutes of ‘LED’ performance ..................................... 26

3.4 Print Circuit Board Design .............................................................................................................. 28

Figure 3.41 – Instructions towards a PCB design ................................................................................. 28

Figure 3.42 – Instructions to a circuit design .................................................................................... 29

Figure 3.43 – Full schematic design translated to PCB ................................................................. 30

Figure 3.45 – PCB design and instructions ........................................................................................ 31

Figure 3.46 – PCB Schematic Design ................................................................................................... 31

Figure 3.47 – PCB schematic & 3D view............................................................................................ 32

Figure 3.48 – PCB mounting solution ............................................................................................ 33

Figure 3.49 – Final design.................................................................................................................. 33

3.5 Design Demonstration .................................................................................................................... 34

Figure 3.51 – Circuit demonstration ..................................................................................................... 34

Figure 3.52 – Demonstration of program used ................................................................................ 35

Chapter IV – Cost of Materials ......................................................................................................... 36

4.1. Cost and Materials ......................................................................................................................... 36

Chapter V – Lateral Thinking ............................................................................................................... 37

5.1 Lateral Thinking – Other Possible Uses ......................................................................................... 37

Chapter VI - Conclusion .................................................................................................................... 38

6.1. Conclusion ..................................................................................................................................... 38

Chapter VII - Bibliography ................................................................................................................ 39

Bibliography ......................................................................................................................................... 39

Chapter VIII - Appendix .................................................................................................................... 41

Appendices ............................................................................................................................................ 41

Appendix 1 – PIC detailed block diagram ............................................................................................ 41

Appendix 2 – Instruction set ............................................................................................................. 41

Appendix 3 – Complete Program .................................................................................................. 42

Appendix 4 – Program Flow Chart ....................................................................................................... 46

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Summary The project relates to the design of a structured program composed in assembly language

that provides the feasibility of applying it to a variety of applications regarding an event. In

this case scenario, the program forces the microcontroller (PIC series) to trigger a light

emitting diode (LED - powered by a MOSFET transistor) every 6 hours for a timescale of 4

minutes. To complete a program as such, a prototype of a 24 hour digital clock was provided

to observe and analyse the program behind it. The 24 hour clock program became a great

assist to arrive at complete knowledge of the system’s working conditions, in relation to the

development of the project.

The report examines a step by step process designed to arrive at the completion of a

working program, providing extended abilities for the programmer to manipulate the

program with regards to their specifications.

Key points; Event – Program – Assembly Language – Trigger – LED – Every 6 hours – For 4

minutes

The step-by-step process consists of a direct approach that provides useful techniques on

how to set-up a simple program; distributing a learning curve that also includes timers and

delays. This allows the project to grow by stabilising the way of thinking. The report is

considered to deliver an advance level of knowledge to the reader regarding the PIC16F84

(or assembly language), explaining in complete detail how the device works, how the

processor links (to produce such performance) and how to program it using the exact

project requirements, as well as, a personal specification at different time scales, triggering

an event.

The objectives of the project and the desired performance were successfully achieved.

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Chapter I - Introduction

1.1 Introduction to Microcontrollers Microcontrollers are nowadays used in a range of off-highway machinery (i.e. most

electronic devices). The first microcontroller was developed around the year 1970 and 1971

and ever since the first microcontroller; around 2 billion are developed and processed every

year. Microcontrollers are very efficient in many ways and are characterised as one-chip

computers. These one-chip computers are everywhere; an average house has around 100

one-chip computers and don’t go a day without getting used. One-chip computers are

situated within electrical devices, such as; thermostats, clocks, automobile engines, gadgets

and many other appliances. Figure 1 shows the first microcontroller ever invented and

figure 2 illustrates various microcontrollers applied on a variety of devices. [1].

Figure 1.10 – First ever microcontroller

[1]

Figure 1.12 – Different types of microcontrollers used in a range of devices

[13]

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[15](ii)

Project aim:

The aim of the project is to achieve a successful program that triggers an

event at specified times, with regards to the project brief. The program

will be demonstrated in a full schematic diagram of a circuit

implemented in Proteus. The circuit should be composed of a

microcontroller that controls an LED being powered by an NPN

transistor.

Project Objectives:

To develop a well-structured report regarding the complete design of

the project. The report must be divided into segments, segments that

dictate the development of the design and builds up to deliver

knowledge and understanding with regards to the systems performance

and production.

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Chapter II - Literature Review

2.1. Microcontroller - Design & Architecture Microcontrollers [MCs] vary from a range of sources, and a plethora of designs. This project

is restricted to the microchip PIC series, 16F84 in particular.

Memory capacity varies widely from 0.5Kbytes to 512Kbytes of ‘Read Only Memory’ [ROM]

and 16bytes to 128Kbytes of ‘Random Access Memory’ [RAM] with 1Kbytes of flash

EEPROM. [2][3]

The PIC microchip series have become quite vast, microcontroller versions range from 8, 16

and 32 bits. Nowadays, microcontrollers are designed based on flash EEPROM; they can be

easily programmed and reprogrammed. [2][3]

The PIC 16F84 in particular consists of a Harvard Architecture design. MCs with Harvard

Architecture are called Reduced Instruction Set Computing (‘RISC’) microcontrollers. MCs

are designed in one of two architectures, Harvard or Von-Neumann [VN] known as Complex

Instruction Set Computing (‘CISC’) (I.e. Harvard = RISC, Von-Neumann = CISC) [2].

Harvard is an updated version of VN. Harvard allows a greater flow of data in and out of the

CPU at higher speed. This is caused by the Harvard design, having the data and address bus

separately connected. Additional information about microcontrollers will be discussed

further in the report. [2]

The main advantage of the ‘PIC16F84 MC’ is having a total of 35 instructions, all available

for execution in 1 instruction cycle except for the ‘JUMP’ and ‘BRANCH’ instructions. [2][3]

A microcontroller has a very basic operation which is best described in a structured diagram

explaining the importance of its operation. Figure 3 provides an example of the structure

and performance based on real world operation.

Figure 2.10 – Basic microcontroller structure & operation

[3]

The illustration above is based on vital entities performed when operating. Appendix 1

illustrates a more detailed diagram.

CPU

Input/Output

Memory

User/Real Kit

BUS

Clock

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2.2. Microcontroller and microprocessor Dissimilarities Microcontrollers are typically embedded systems. An embedded system is composed of an

external processor, followed by an internal design regarding memory and I/O ports. As

both, the memory and I/O ports are integrated; the circuit is miniature, making a great

invention that is usually used in compact systems/devices, with the advantage of buying

them at low-cost. They are extremely beneficial as external components as they operate at

low voltages, keeping power consumption at a minimum. An extended functionality is also

available; power saving and idle mode, decreasing its power consumption even further.

Therefore, it has the ability to run with stored power (batteries), at an exquisite speed

performance, since all components and operations are integrated. The design also consists

of more registers than the microprocessor and therefore, makes the programming of the

software straightforward. The program memory in the microcontroller is designed with its

own memory location. [1][9]

Microprocessors are based on computer systems. The main difference between the two is

that a microprocessor is basically a processor and nothing else. Memory and I/O

components are adapted externally, therefore, forcing the design of the circuit to be bigger,

as well as, inefficient. Having all microprocessor components externally connected, requires

more power, making it impossible for stored power to create an efficient voltage-drive,

forcing the mains to power-up the circuit. Microprocessors are usually not found in compact

systems as externally linked components / drives make the system slower. Figure 4

illustrates a block diagram of both, the Microprocessor and Microcontroller. [9]

Figure 2.21 – Microprocessor and microcontroller disparity

[9]

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2.3. Central Processing Unit (CPU)

CPU focuses on most calculations performed during execution, as well as, present

operations of all other units. CPU is best described as a synchronous device where all the

statistics are intercepted in parallel format, processing at a speed directly proportioned to

the clock. CPU’s are designed to follow some form of operation. The operation designed for

most CPU’s to follow involves four steps (fetch, decode, execute and write-back). [4]

Fetch – Reading an instruction represented in computer language (binary/hexadecimal)

from a memory location indicated by the software program. Memory locations are mapped

in the program counter. The program counter stores a value that determines its current

position within the program for the CPU to read. The length of the instruction determines

the size of memory that is required and therefore the program counter is incremented by

the required size. [4]

Decode –The instruction obtained is broken down into separate entities and is divided to

different portions of the CPU. Each division is significant to different parts of the CPU where

each stat is acknowledged by the CPU’s ‘Instruction Set Architecture’. Operands are known

to be the remaining portions of the instruction. Remaining portions are normally values,

which defines the action required for additional operation. [4]

Execution – At this point the CPU has read the instruction and now understands its

requirements. Therefore, different portions of the CPU work together performing the

desired operation. [4]

Execution refers to a sequence of stored instructions known as the program. This program

signifies a series of data (usually represented in binary / hexadecimal figures) and are then

stored in a non-volatile fashion within a memory location. [4]

If any other operations are requested, such as; input logics or arithmetic. The ‘Arithmetic

Logic Unit’ is then activated to a set of I/O ports (input/output) and takes care of it. [3]

Write-back – Defines the write back of any results to the required memory location

(ROM/RAM). [4]

Arithmetic and Logic Unit – This particular register focuses in all arithmetic and logic

operations where it utilises a source known as the regulator to keep a referenced voltage

and an accumulator used for logic operations.

http://microprocesser.blogspot.co.uk/2009/09/cpu-operation.html

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2.31. Memory Computer memory stores memory in slots (memory locations). The program stored should

remain unchanged for good performance. Therefore, any data that requires the CPU to read

and follow should be stored in the ‘Read Only Memory’ (ROM – memory remains stored,

even when powered off and cannot be easily altered).

There are two types of memory, ROM as explained above and RAM. RAM is a term used for

‘Random Access Memory’. RAM is also read by the CPU, however, the CPU understands

that memory being stored in this type of location, may require a change of variables without

distracting any other location (RAM – Memory can be accessed randomly at any point in

time from any physical location allowing quick access and manipulation). [3]

2.32. Input and Output (I/O) Without this operation the microcontroller might be useless. Input and output is vital as it

allows the microprocessor to connect to the outside world. Allowing data transfer from the

microcontroller to external devices and peripherals. Data transfer may contain one of the

following:

- Status

- Control signals

- Data

Input and output’s - General purpose for performance:

1. Reconsider time difference between the microprocessor and peripherals.

2. Making sure data is formatted correctly.

3. It should handle the ‘status’ and the ‘control of signals’.

4. Must supply the correct voltage and current levels

5. [3]

Input stage makes sure that information is processed into systems. Such as, information

read from sensors or switches. It is defined as ‘Read Variable Operation’. [5]

Output stage is involved in processing information to the outside world and displaying the

results, normally used to control equipment. This is defined as ‘Write Variable Operation’.

[5]

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2.4. Microcontroller Organisation The best way to consider the organisation of microcontrollers is to refer memory and I/O as

a series of discrete memory locations. Each of them encoded with its unique location

individually stored in binary words. Each word is considered to have 1 byte of data available.

Memory and I/O locations may be referred to as 8 times D-type flip flops connected in

parallel and is characterised as an 8-bit storage register. [3]

Buses are known to be crucial in any computer system. Microcontrollers normally involve

three buses performing different tasks.

- Address Bus

- Data Bus

- Control Bus

Buses are designed to transmit words of command information via sets of wires connected

in parallel. [3].

The address bus is for the CPU to transmit memory addresses back and forth. Allowing

transportation of data to be retrieved or deposited from correct locations. In other words, a

system used to address the main system memory. The address bus can vary from 16, 20 and

32 bits large. [3][6]

The data bus transports data in a bi-directional form, ranging from the CPU, memory and

I/O ports built in 8 or 16 bits wide in size. In other words, it allows data transmission from

one component to another on a mother board, system board or computer systems. [3][7]

The control bus on the other hand, decides which bus is required for data transmission. The

CPU utilises it to communicate with other entities inside the machine and a series of status

bits indicate the type of bus access required to take action. Signals that relate to read, write

and interrupt, allows the CPU to “visualize” and monitor the different parameters within a

computer system. Its exact composition varies amongst processors. [3][8]

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2.5. Microcontroller - Software program Microcontrollers can be programmed using a variety of programming languages, such as C,

Assembly or BASIC, for instance. However, the language that contributes with the finest

performance is known to be the assembly language. Assembly language has excellent

reviews and is mostly preferred regarding engineers. It works amazingly well when

programming inexpensive MCs, as it drives them to the best of their abilities. This type of

language has one thing that no other program encounters; that is complete control of all

instructions followed by the CPU, along with memory and time control throughout each

instruction of the program. An assembly program is composed by reviewing the main

concept that needs to be achieved in extreme detail, following the steps that a computer

requires to ‘understand’. In other words, the complexity of the assembler has to be reduced

by writing in well defined format. Every CPU uses a different type of assembly language;

Pentiums, PIC microcontrollers, Microprocessors and Motorola 68000’s, making it harder to

read/write, learn and understand. [9] Appendix 2 illustrates the PIC’s instruction set.

PIC16f84 is a high-tech microcontroller which is characterised as a micro-computer. Both,

the microcontroller and the microprocessor are much alike, having a sort of linkage with the

following:

Central processing unit (CPU)

Program memory (PROM)

Working memory (RAM)

Input / output (I/O)

Program counter

Registers – Special Function (SFR) & General Purpose (GPR)

Arithmetic Logic Unit (ALU)

Timers

Etc

Although a computer is designed in a higher level of complexity, the microcontroller is an

amazing design. The CPU is usually defined as the brain’s of a computer where most

calculations take place, sometimes referred as central processor or the heart of a computer.

As discussed earlier, the ‘16f84’ has a desirable advantage which consists of flash EEPROM.

In other words, flash EEPROM is considered to be a standard design which allows you to

erase or record data electrically, as well as, preserve any load of data when powered off. [3]

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2.6. Research of Program Development Programming this type of project in assembler requires knowledge on the software process

operations, such as:

- Registers

- Banks

- Program execution

2.61. Registers Registers are based inside the MC; allowing other functionalities/operators to read from it,

write on it or composite. Figure 5 illustrates the registers located in the PIC16F84, normally

used for mapping.

Figure 2.610 – Map Register

[10]

As illustrated above, the register consists of 2 divisions named ‘Bank 0’ and ‘Bank 1’. They

work together to perform different tasks, allowing data transfer flow correctly. Low bank (0)

is used for data manipulation, allowing the operator to set bits high or low. High bank (1)

controls the MC’s operation, allowing the user to decide which bits are set as ‘PORTA’ and

vice versa for ‘PORTB’. A normal operation using both banks consist of setting ‘PORTA’ bits /

pins as input/output (in bank 1), followed by setting up the bits to high or low (to 1 or 0) for

a response to a particular pin (in bank 0). Each register inside the MC correspond to a

specific address. These addresses are extremely important as it tells the PIC where

information should be stored (03h=STATUS address, notice that 03’h’ means the numbers

are in hexadecimal). The STATUS register is referred as the most common instruction

normally being used to allow the PIC to switch from ‘bank1’ to ‘bank0’ or vice versa. TRISA

& TRISB are two instructions used to identify which pin of ‘PORTA’ is set as I/O (TRISA) and

which pins of ‘PORTB’ are set as I/O (TRISB). [10] Ps. TRISA/B can both be set as inputs or

outputs, hence, I/O.

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A byte consists of 8 bits, where each bit corresponds to some sort of action. For example,

switching from bank 0 to bank 1 requires bit number 5 to be set to high (1), and vice versa

to switch back. More detailed information about each register and what each bit

corresponds to can be found in the PIC series datasheet (in this case PIC16f84, datasheet

ref- [10]).

Telling the PIC to set pins as I/O is relatively straight forward, a zero or a one sent to the

corresponding pin/bit does the job. Therefore, in relation to the PIC, PORTA consists of 5

pins, RA0 – RA4, the bits available for it ranges from 0 – 4, summing up to 5 in total. Pin,

RA0 links with bit 0, RA1 with bit 1 and so forth, for example, setting the ports to Input and

output – RA0 to RA2 as input and the rest as outputs. Figure 6 illustrates the literal transfer

required.

Figure 2.611 – Binary values determine I/O ports

PORTA RA4 RA3 RA2 RA1 RA0

Binary Values 0 0 1 1 1

Bit Value 4 3 2 1 0

Number of Bits 5 4 3 2 1

The table above illustrates values required for ‘TRISA’, ‘TRISB’ operates in the exact same

format. However, remember that TRISB has more pins, i.e. more bits [8, ranging from 0-7].

Once the I/O ports have been set to one of the TRIS registers, the next step involves moving

back from bank 1-to-bank 0; to permit communication between the registers from that

bank. This is done by clearing ‘STATUS’ bit 5, as mentioned in the previous sectors.

Therefore, when the ‘STATUS’ has been cleared, ‘PORTA’ can then be set, using the same

format setting the bit/pin number from the port to high (1) and so forth with ‘PORTB’. [10]

Before setting the ports to a high logic, another register has the necessity to be involved.

This register is known as the ‘working register’ (‘W’ register). The ‘W’ register allows literal

content values to be assigned to it, therefore, once the ‘W’ register has been assigned with

a value, it can then be added to another or be moved. Assigning two values to the ‘W’

register will then over-write the previous content. [3][10]

This is the basic process follow for the design of a simple program.

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Chapter III – Research Methodology

3.1. Design and Development of the circuit and software Reducing project simplicity is the best way to start. Therefore, designing the circuit through

a simple program aimed just to flash the LED reduces complexity. A block diagram regarding

the development of the circuit schematic and program is illustrated in figure 3.11 and 3.12.

Figure 3.11 – Circuit Block Diagram

LED Circuit – powered by transistor

Voltage Regulator Circuit(Applies 5V to MicroC)

Software program (microcontroller) including

external set-up (I.E-MCLR & Osc1+2)

INPUT SOFTWAREINPUT OUTPUT

Figure 3.12 – Program development block diagram

Develop basic program to Flash an LED

Set-up Timer0 and Prescaler

Design a 1 second delay subroutine

Set-up Input / Output Ports

Inherit from 1 sec delay subroutine and extend to 6

seconds delay

Inherit from 6 sec delay and develop a 4 Min delay

Inherit from 4 min delay and extend to 1Hr Delay

Use 10 min delay subroutines to test the

program

At this point in time any specs regarding timing

delays should be straight forward

Program development Block Diagram

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3.11 Circuit requirements - PIC16F84

- Oscillator circuit,

- Resistors

- MOSFET Transistor

- LED

- Voltage Regulator

- MCLR Set-up

Figure 3.13 illustrates a complete schematic of the circuit design.

Figure 3.13 – Circuit diagram

The circuit schematic will be explained in different parameters, each parameter was

explained with regards to the illustrated diagram.

External Oscillator Circuit – An external oscillator is required for asynchronous communications, it

generates clock pulses so that all operations internally are synchronized, the circuit illustrates two

27pF capacitors, however, as the crystal was reduced to 32768Hz, it

operates at low-power (LP), hence, capacitor values ranging from 68-

100pF was required, therefore, 68pF was used instead for everything

to operate accordingly. Datasheet provides more information

regarding the PIC.

MCLR circuit set-up – MCLR set-up is vital, as it should never be left floating. The MCLR pin is known

as a reset pin, it is used to power up the microcontroller with enough voltage drive to perform all

operations, though, if the voltage is lower than the maximum input low voltage, typically 1V for a 5V

operation, the system will reset. This only occurs when the MCLR pin is enabled, in the other hand, it

can be internally tied up to VDD and therefore, used as an input.

External

oscillator

circuit, -

Designed to

count directly

proportioned

to the internal

clock (Osc).

LED circuit -

powered by a

MOSFET

transistor,

controlled by

the PIC.

Voltage Regulator

Circuit - Designed

to provide a fixed

5volts input to the

circuit from a high

voltage supply.

MCLR circuit

set-up – Allows

the power

supply to settle.

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In this project, MCLR pin has been configured with RESET functionality, with a push button/ switch

to manually reset the system’s operation.

Voltage Regulator – Voltage regulator is an extremely useful source for protection regarding the

circuit. For instance, the circuit requires 5 volts in to power up the microcontroller and from 2 - 3

volts approximately to power up the LED, thus, if you plug a 10 Volts supply, the circuit /

components will be jeopardised. Therefore, the voltage regulator acts like a safety net that no

matter how much voltage is being supplied, the voltage will be reduced to 5 volts. (19)

LED Circuit – The LED is being powered by a transistor (MOSFET, N-Channel), as specified in the

project brief, however, a MOSFET / normal NPN transistor can be applied, though; a MOSFET has

been selected instead. Reason being, the MOSFET is voltage based and the NPN is current based.

This means that a MOSFET does not require a resistor between the PIC and the transistor, as

voltage is usually stable, current, in the other hand, may require some control

(resistor) to avoid the current spikes. The gate-source breakdown voltage is 2.5

volts approximately; hence, no further calculations are required to power-up the

LED, (as long as 2-3 volts is being supplied to it). Figure 3.13 proves 2.2 volts

approximately is being supplied. (16)

Following the concept explained earlier about programming a simple program is

demonstrated in figure 3.14, test 1. (17, 2002)

Figure 3.14 - Program test1

STATUS equ 03h ;Assigning STATUS to equal that address (03h)

TRISB equ 86h ;Assigning TRISB to equal address (86h)

PORTB equ 06h ;Assigning PORTB to equal address (06h)

Start

BSF STATUS, 5 ; moving to bank 1 via Status

MOVLW B'00000000' ; PORTB as Output

MOVWF TRISB ;Moving data to TRISB

BCF STATUS, 5 ;Moving back to bank 1 by clearing the status

BSF PORTB, 0 ;Setting bit '0' to high =1

MOVLW B'00000000' ;Moving all pins to the general purpose reg 'W' register

MOVWF PORTB ;Moving the literals to trisB to set the port

GOTO Start ;Going back to start - making a loop

Figure 3.15 is an illustration of the circuit schematic and LED performance regarding the

program.

Source

Gate

Drain

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Figure 3.15 – LED flashing, on & off

1

Circuit 2 demo (LED OFF)

2

The circuit illustration above demonstrates from the LED’s performance, that the program is

in good working condition. Further progression results more complex, as it requires a timer,

known as TMR0 in pseudo code, a prescaler set-up for the timer and delay subroutines to

delay the LED’s performance with regards to the project specifications. These parameters

will be explained and demonstrated in the following chapters.

VDD proves that

both circuits are

operated and

working, even

though the LED is

OFF on circuit 2.

This light

demonstrates

when the PIC

turns off the

LED, as it

lights up

when LED is

on and goes

off when LED

is off.

Remember

this blue

(off) light,

and LED (off)

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3.2. Timer0 Module & Set-up The timer module is a function within the PIC that can be used to control various entities’

performance when dealing with time, delays and interrupts.

The features available within this module include:

- 8-bit timer/counter

- Readable and writable

- Internal or External clock select

- Edge select for external clock

- Interrupt on overflow from FFh to 00h

The timer0 Module can be characterised using an illustrated diagram of its process and flow.

See figure 3.2.

Figure 3.21 - TMR0 Block Diagram

Timer mode can be selected by clearing the bit T0CS, this will cause the timer0 module to

increment without a prescaler, every instruction cycle. On the other hand, counter mode

can be selected instead by setting the bit T0CS (OPTION_REG [bit5]), causing the counter

mode to increment either on every rising or falling edge of the RA4/T0CKI pin. In order to

select the rising edge or falling edge, a special bit must be set or cleared, known as ‘Timer0

Source Edge’ bit select. Setting this bit located in the OPTION_REG [bit4], enables the rising

edge. [11].

Calculations are required to perform timer/counter functions. However, knowing the speed

at which the external oscillator (clock) is running at is significant. The timers in the PIC series

run at a speed of ¼ (0.25) to the clock speed. Therefore, knowing the crystal component

value identifies the calculation required for the exact speed the PIC is running at. Say the

crystal value is 1MHz, i.e. ¼ of 1 MHz = 250 KHz. At this frequency the clock is performing

quite fast. Therefore, lighting up an LED for 1 second involves the timer to count 250K

pulses. (17, 2002)

As explained previously the option register requires a set-up to perform the requirements

that are necessary for the delays. Slowing down the timer would increase the possibility of

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regaining accurate time measurements by reducing the number of cycles the

microcontroller is required to count to make 1 second. A varied factor of 2, 4, 8, 16, 32, 64,

128, 256 are available within the prescaler. These factors are known as prescaler ratios and

are used to divide the number of cycles per second by each corresponding ratio. If 250K

cycles would be equivalent to 1 second; setting the prescaler to 256 will cause a calculation

of 250K/256= 976.5625 (equivalent to 1 second once it is set). [11]

Due to the clock being so high in frequency, it increases complexity regarding the maths.

Reducing the internal clock frequency to 32 KHz slows down the process making delays

easier to perform. By using 32,768 KHZ as the external oscillator value allows the maths to

be straightforward and exact (whole digit; no fraction). ¼ of 32768Hz = 8192Hz, frequency =

1/time. Therefore, 8192Hz results as 8192 pulses, counting 8192 pulses will result as 1

second. However, 8192 pulses still results as a lot to count. This is when the prescaler is

introduced. [11] (17, 2002)

3.3. Prescaler Set-up The prescaler is known to be an 8-bit timer utilised as one of two possible timer modules;

timer0 module or watchdog timer [figure 11]. The prescaler can only be used for one or the

other, due to one bit being available as a prescaler set-up [PSA] in the option register. If the

bit PSA was cleared, a set-up will automatically be set for the timer0 module and vice versa,

bit set would automatically be set for the watchdog timer.

Once it has been decided, there are another 3 bits named PS2:PS0. These are then used as a

ratio set-up for the timer as mentioned previously. Figure 3.3 illustrates the prescaler rates

and option register functionalities on both timer modules. [12].

Figure 3.31 – Option Register functionalities & Prescaler rate

21 | P a g e

The illustration above demonstrates how to assign a definitive prescaler value for the WDT

& TMR0 module depending on the peripherals of the system. The prescaler values are

simply categorized into ratios to demonstrate the 3 bit binary format.

As illustrated on the figure above, it states how to choose different ratios by using diverse

binary values. [12].

Test 2 – Worked example 1 on time delays The code has been generated to create a 1 second time delay between each interval within

the LED (off [1sec] on [1sec]). Figure 3.32 demonstrates the code generated to perform a 1

second delay. (17, 2002)

Figure 3.32 – 1 Second time delay subroutine

DELAY1 CLRF TMR0 ;Start timer at Zero

LOOP1 MOVF TMR0,W ;Read timer0 into working Reg

SUBLW .32 ;Time - 32 = 1 seconds

BTFSS STATUS,ZERO_BIT ;Check time W=0

GOTO LOOP1

RETLW 0 ;Time is 32 = 1sec, Return

;====================================================================

; CONFIG SECTION

START BSF STATUS,5 ;Turns to bank1

MOVLW B'00011111' ;5 bits PORTA as inputs

MOVWF TRISA

MOVLW B'00000000' ;PORTB = output

MOVWF TRISB

MOVLW B'00000110' ;Prescaler, is/128,With regards-Fig3.31

MOVWF OPTION_REG ;Timer is 1/32

BCF STATUS,5 ;Back to bank 0

CLRF PORTA ;Clearing PORTA

CLRF PORTB ;Clearing PORTB

START2 BSF PORTB,1 ;Turn on LED

22 | P a g e

CALL DELAY1 ;wait 1 second

BCF PORTB,1 ; Turn off LED


GOTO START2 ;Repeat from start2

Evidence of approximately 1 second delay is demonstrated in figure 3.33

Figure 3.33 – 1 second delay illustration

At this point the program has successfully completed a delay of approximately 1 second;

therefore, 6 seconds delay should be easily done by just incrementing the .32 (equivalent to

1 second) on the instruction ‘SUBLW’ by performing the calculation, 32 * 6 = 192. I.e. 6

seconds delay is now set up. Hence, Delay1 can now be called Delay6. Figure 3.34 illustrates

the program demonstration.

At 1.001

seconds

light is still

on

At 1.25

seconds Light

is off

To freeze the timer exactly on the dot is

basically impossible; however, the exact value

lies between 1 and 1.2. As a result, one second

delay was a success.

23 | P a g e

Test 3, worked example 2 on time delay (6seconds)

Figure 3.34 – Time delay increased to 6 seconds



SUBLW .192 ;Time - 192 = 6 seconds (32*6)


GOTO LOOP1 ;Time still not 0

RETLW 0 ;Time is now 0 = 192= 6sec, Return

The idea of 6 seconds delay is the process of making a 4 minutes delay as well as, a 1 hour

delay. By calling the 6 seconds delay 5 times will provide a 30 seconds delay, consequently,

by generating a counter of .8 will then cause a 4 minutes delay (as 30 seconds is equal to ½ a

minute, therefore, ½ *8 = 4). Meaning that by incrementing the count to a higher value will

allow a time delay of a larger time scale. An hour delay will result as a count of 120 (i.e. 120

* ½ = 60 minutes) calling this delay 6 times will add-up to the required 6 hour delay, a count

of 240 will also have an advantage of using a smaller program. However, a long ‘count’

process requires more compensation regarding time offsets. This is the reason why setting

up small delays provides more accurate results. Figure 3.35 demonstrates test 4 on a 4

minute delay subroutine set-up. (17, 2002)

Test 4 – Figure 3.35 – Four minute delay

FOUR_MINS_DELAY

MOVLW .8 ;Time .8 / ½ minute = 4mins

MOVWF COUNT ;put .8 into COUNT

LOOP2 CALL DELAY6 ;wait 6 seconds

CALL DELAY6 ;wait 6 seconds



CALL DELAY6 ;wait 6 seconds = 30 sec

DECFSZ COUNT ;decrementing by 1 from count

GOTO LOOP2 ;Still not Zero

RETLW 0 ;Time is now Zero = 4mins, time to execute

24 | P a g e

Manipulating the count value speeds up the process when testing, as 1 hour delays become

more time consuming. Figure 3.36 illustrates a 4 minute delay from 2 displays and figure

3.37 illustrates the program designed for a 1 hour delay.

Figure 3.36 – Circuit test when calling 4 minute delay

1 2

Test 5 - Figure 3.37 – 1 hour delay

HR_DELAY MOVL .120 ;Time 120 (30 seconds * 120 =3600 /60mins =

60mins = 1hr delay)

MOVWF COUNT ;put 120 in to count

LOOP CALL DELAY6 ;wait 6 second




CALL DELAY6 ;wait 6 second, = 30 seconds

DECFSZ COUNT ;Decrementing count by 1

GOTO LOOP ;Time still not Zero

RETLW 0 ;Time is now zero = 1 hour, time to execute.

(17, 2002)

Test 6 – Testing both delays together

As mentioned previously, manipulating the program is required to speed up the testing

process, therefore, instead of testing at every 1 hour interval; it will be every 10 minutes

after the 4 minutes delay has been executed (a ‘COUNT’ value of 20 [* ½ = 10]). The

expected result should appear as the LED lighting up every 10 minutes for a time scale of 4

minutes. Figure 3.38 illustrates a demonstration of the program execution being simulated.

25 | P a g e

Figure 3.38 – Program executing with an LED response

1 2

According to the illustration, it can be seen that the time scale calculation was working as

instructed, however, a slight miscalculation was experienced. The problem is related to the

‘COUNT’ value provided on the delay subroutine designed to act every 10 minutes. Reason

being, having provided the first delay to light up the LED, already uses 4 minutes of the 10

minute time scale i.e. a 6 minute subroutine is required instead, reducing the time scale

length from 14 to 10 minutes. Figure 3.39 shows a new rearranged program fitting the

required time scale. This error provided a positive outcome regarding miscalculations of

delays; due to knowing a 56 minutes delay is required with a 4 minutes delay to make 1

hour (simple mistakes can easily be made, therefore, testing is crucial).

Figure 3.39 – Rearranged program

The program calls a four minute delay (shown previously), then waits 6 minutes

(SIX_MIN_DELAY) before calling it again and then repeats the process.

SIX_MIN_DELAY MOVL .12 ;Time 12 (30 seconds * 12 =360 /60mins = 6mins)






CALL DELAY6 ;wait 6 second, = 30 seconds



RETLW 0 ;Time is now zero = 6 minutes, time to execute.

Figure 3.310 illustrates the rearranged program’s performance.

26 | P a g e

Figure 3.310 - Test example

1 2

3 4

During the practical assessment of the new program, a series of acceptable results were

discovered. Finally, allowing the program to be developed with a 56 minute delay

subroutine (.112 ‘COUNT’ value) that creates a time scale of 1 hour. These 1 hour delays can

be called as many times, depending on the purpose of the event. However, always keeping

in mind that setting the port linking with the LED will provide a response, it will not respond

otherwise. Figure 3.311 shows the complete program, excluding delay subroutines (start-to-

end), appendix 3 illustrates the whole program.

Figure 3.311 – 6 Hour delay program with 4 minutes of ‘LED’ performance START BSF STATUS,5 ;Turns to bank1

MOVLW B'00011111' ;5 bits of PORTA as inputs

MOVWF TRISA ;put input ports in TRISA


MOVWF TRISB ;put output ports in TRISB

MOVLW B'00000111' ;Prescaler is set to /256




27 | P a g e



CALL FOUR_MINS_DELAY ;Four mins delay


CALL DELAY56 ;wait 56mins, 1ST HOUR Delay


CALL DELAY56 ;wait 56mins, 2ND HOUR


CALL DELAY56 ;wait 56mins, 3RD HOUR


CALL DELAY56 ;wait 56mins, 4TH HOUR






END

As illustrated on the program, it can be seen that there are several ways on how to create

delays. The program generally contains three delays;

- A delay making up for 6 seconds

- A delay making up for 56 minutes

- A delay making up for 4 minutes

With the aid of these three delays, TMR0 and prescaler set-up, the project brief was

successfully achieved and proven to be ‘fully working’. As displayed, the delays are being

called 6 times in this program to compensate for 6 hours. Due to the count-down occurring

from ‘.112’, it makes it possible to start counting from any number between 0-255 (as the

counter only counts in bytes, and 1 byte = 1 memory location ranging from 0-255), counting

further will require 2 memory locations, making it more complex to append. Therefore, 2

hour delay could simply be appended into the counter. ‘120 = 1 hour, i.e. 240 = 2 hours; as a

result, ‘.240 - .8 (the 4 minutes delay) = .232’. A 2 hour delay combined to make 6 hours,

offers the advantage of making the program slightly smaller in length and memory,

providing a faster execution. The disadvantage relates to a larger offset when ending the

counter (as mentioned previously), precision is key in engineering, therefore, the use of one

hour delay will result as more accurate towards the desired outcome. Appendix 4 provides a

flow chart of the program, usually the flow chart should be made before the program is

even thought about, as it provides an idea of what is required in program development.

28 | P a g e

3.4 Print Circuit Board Design The PCB is an important parameter regarding the design, as it is what provides the design

with a fully linked up circuit for real world application. The PCB was developed using ‘Easy-

PC’ software. It provides a great amount of functionalities and is extremely user friendly,

hence, Easy-PC. Firstly, before being able to design the PCB, the system needs to know what

circuit is being implemented before the PCB transformation. Therefore, a project schematic

design needs to be created. Figure 3.41 will illustrate the steps necessary to begin the

design.

Figure 3.41 – Instructions towards a PCB design

Schematic design created & saved to file.

29 | P a g e

After saving schematic this window appears, allowing the circuit design to be created as a

schematic diagram. Therefore, choosing components from the libraries is required. Figure

3.42 provides instructions for a circuit design.

Figure 3.42 – Instructions to a circuit design

Once the circuit has successfully been developed, having met the requirements to convert it

to a PCB ‘Integrity Check’, translating schematic to design is required. Figure 3.43

demonstrates the next process regarding the complete schematic diagram.

Add component (Provides the ability

to search components from libraries)

Add schematic connection (provides

abilities to link components)

Add component and schematic connections

are the most common functions used, to

find out what each of the others do/mean,

just placing the pointer over the icons will

determine what they are.

30 | P a g e

Figure 3.43 – Full schematic design translated to PCB

Once the schematic has successfully been translated to a PCB design, building it up as

compact as possible is significant. Components can be selected and dragged to the PCB

schematic sheet from the component bin, having dragged all components, routing the

components is necessary with no overlaps regarding the nets (routes). If they do overlap,

there is a functionality that allows the nets to be placed at the bottom/top layer of the

board, solving many problems. Figure 3.44 illustrates the PCB design with relevant

instructions included to aid users.

Rainbow icon allows the

background sheet /

components colour to

be changed personally.

Integrity checks that the

circuit is linked

appropriately.

31 | P a g e

Figure 3.45 – PCB design and instructions

The following design in figure 3.46 will illustrate the final PCB with no sharp corners, a

copper layer (top and bottom) and fully labelled. The ( ) symbolises a demonstration of

the eliminated sharp corners, though it does not show all eliminated corners to provide a

good visual display of the schematic.

Figure 3.46 – PCB Schematic Design

Top Layer schematic with copper poured.

Side bar – provides; Layers,

Component bin, Add

component and Notes.

Shows all created files within

same project.

Left side icons follows the same concept as circuit schematic, placing pointer over

any icon provides a brief instruction regarding its operation. Icons in this side bar

are more sophisticated, also displaying copper pouring icon and more.

Design conclusion - The

idea of building a good PCB

revolves around; making it

compact and tidy, using a

design approach that

would reduce noise as

much as possible. I.e.

copper layers (bottom &

top), no sharp corners

cause it radiates.

32 | P a g e

Middle layer drill holes and zero nets.

Bottom Layer schematic with copper poured and direct routes from pin to pin present

(made to reduce complexity of overlapping routes).

Routes demonstrate the no sharp corners rule, to reduce noise interference as much as

possible. Figure 3.47 illustrates the design with all present layers in the same visual display,

followed by a high quality 3D view of the PCB final design.

Figure 3.47 – PCB schematic & 3D view

33 | P a g e

Last but not least, the board requires some sort of design to allow easy mounting, therefore,

arranging a way of employing it to an existing device is necessary. Figure 3.48 illustrates the

solution.

Figure 3.48 – PCB mounting solution

The solution as illustrated was solved by inserting drilling holes on each corner of the PCB

design for mounting purposes. A system design rule check was performed also, proving that

the PCB is in perfect condition with absolutely no errors. PCB is now ready for reproduction.

Figure 3.49 – Final design

Layer

thickness

can also be

reduced for

ease of

application

.

This was done

by deleting

unwanted layers

from –

Settings>Design

Technology>

Layers (Adv.

making a

compact mount)

Size: 35.2 x 36.5mm, Length: 143.41mm

34 | P a g e

3.5 Design Demonstration The design was built to demonstrate that the circuit was in full working condition. However,

the program has been manipulated with a much smaller time scale, ranging from 4 seconds

on, and 1 second off. Figure 3.51 illustrates the circuit model built on a breadboard, being

powered by a 9 volt battery (also proving a portable design).

Figure 3.51 – Circuit demonstration

1

2

3

Demonstration proves that the circuit is working accordingly to the designed program. It can

be seen that a slight offset regarding the timing is present, due to the creation of the

program being constructed & tested on a simulator, as shown in previous chapters; the

simulator contains a slight offset when compared to real-time. However, when analysing

the time of trigger, the time-offset can be repaired by applying a slight delay to compensate

the time required. Although, achieving an exact value is probably impossible, an

approximate value of +/- 5 percent is achievable. Figure 3.52 shows the program used

regarding the real-time test (3.51, Circuit Demo).

35 | P a g e

Figure 3.52 – Demonstration of program used





GOTO LOOP1 ;Time is still not Zero








;====================================================================

;CONFIG SECTION

START

BSF STATUS,5 ;Turns to bank1


MOVWF TRISB ;Output are set to TRISB

MOVLW B'00000111' ;Prescaler is /256


BCF STATUS,5 ;Turns to bank1

S2

BSF PORTB,1 ;Set (turn on) RB1

CALL DELAY2 ;Call delay2 subroutine

BCF PORTB,1 ;Clear (turn off) RB1

CALL DELAY6 ;Call delay6 subroutine

GOTO S2 ;Go back to loop

End

The program was used for testing; therefore, a small program to cover the demonstration

requirements was developed. All related programs in this project demonstrate a learning

curve with the most fundamental parameter to program development being composed

from loops/subroutines.

36 | P a g e

Chapter IV – Cost of Materials

4.1. Cost and Materials This chapter provides the evidence of costs and materials being inexpensive and affordable,

in relation to microcontrollers and components regarding the full design. Figure 4.1

illustrates a table listing the bills of materials (BOM) when buying in package amounts.

Figure 4.1 – Cost of materials in bundle packages

BOM Required items Package amount Cost Total Cost

PIC - Microcontroller 1 5 £3 3.00

VoltReg 7805 1 5 £3.50 3.50

Push Button 1 5 £2.00 2.00

Battery 1 1 £2.50 2.50

Capacitors 68pF 2 10 £0.99 0.99

Capacitors 0.1uF 2 10 £0.99 0.99

Capacitors 100uF 1 10 £0.99 0.99

Capacitors 10uF 1 10 £0.99 0.99

Crystal 32Khz 1 1 £2.98 2.98

Resistors 100ohm 1 50 £0.99 0.99

Resistors 4 ohm 1 50 £0.99 0.99

Resistors 10Kohm 1 50 £0.99 0.99

MOSFET Transistors 1 1 £1.89 1.89

LED 1 10 £0.99 0.99

Total cost £23.79

Regarding the BOM pricing statistics, it proves the system design as being a low-cost

prototype. If only one was to be designed and manufactured, pricing would result at lower

costs, however, is it worth just buying one of each component, accidents does happen

(components might be faulty). Figure 4.12 illustrates the BOM pricing statistics in a more

detailed format, including the costs as individual components (not all components can be

bought individually). Maplin electronics specialist is an extremely reliable source for

components and other electrical equipment.

Figure 23 - BOM

(18)

As a result, it can be proven that although building just one prototype of the design would

be slightly cheaper, building them in bulk would be more cost effective.

37 | P a g e

Chapter V – Lateral Thinking

5.1 Lateral Thinking – Other Possible Uses The project may result as a very useful project with many possible uses. Nowadays, using

timers to perform executions or to trigger an event at different time intervals are of great

assistance for businesses / farms / etc. Jobs as such might be very easy to undertake,

therefore, why spend money on maintenance when a device can do a better job itself and

be consistent.

Programs are usually developed to complete or operate the easy jobs that for years were

performed by people themselves. A program is usually created to the level and specification

of user’s interest, and unlike people, the device will not require lunch break, fag break, toilet

break or anything else. It will perform the task using 100% of its ability every day or hour;

until the program is changed or updated to undertake other commitments, it is going to

operate as instructed. An example of a program being used at businesses may result from

locking a building automatically every day at the programmed times for security purposes.

These commitments can be fulfilled with no struggle and at low-cost, whereas, a person

would have to go around a building performing them and will await a pay cheque regularly.

This project for example can be used in many different fields and events, these events may

vary from the following;

- A locking system for a building

- Home / business security

- A green house

- Gardening (sprinklers)

- Temperature measures

- Alarms

- Street Lights

- And more

All these possible uses revolves around day-to-day routines/events, providing the solution

of affordable maintenance in a broad range of fields, making the project very useful

outdoors.

38 | P a g e

Chapter VI - Conclusion

6.1. Conclusion The project goal was an important field to study; gaining knowledge and understanding the

PIC series was relevant, to achieve a successful design. The ‘Assembly Language’ for

instance, became a self-teaching experience. However, it demonstrated that revising the

insides of the microchip in detail provided a very good understanding of how the

microcontroller acts when asked to commit or perform an endeavour. Therefore,

programming became slightly easier to learn.

Learning the ‘Assembly Language’ was significant as the language provides the facility of

working with a reduced number of instructions, yet, choosing an approach and actually

programming the microchip was extremely complex. After reviewing different articles and

books, programming became the strategy of an abbreviated ‘ladder’. A ladder, described in

a form of success, for each step closer to the top, meant a step closer to the finish.

Following specific steps of the report is guaranteed to teach a great deal of programming,

changing the way of thinking by providing the essential tools required to develop your own

circuit and program from a different specification at low-costs.

As results have shown; they proved that the project was successfully completed towards the

specified goal.

39 | P a g e

Chapter VII - Bibliography

Bibliography

[1] Electronic Circuits and Diagram-Electronics Projects and Design. (2013, October 23). Retrieved December

8, 2014, from http://www.circuitstoday.com/microcontroller-invention-history

[2] Al-Aubidy, P. (n.d.). Microcontroller Architecture. Retrieved December 4, 2014, from

http://www.philadelphia.edu.jo/academics/kaubaidy/uploads/ES-Slids-lec3.pdf

[3] Author: Caerwyn Ash – Course Notes

[4] Processor, M. (2009, September 10). Microprocesser. Retrieved December 6, 2014, from

http://microprocesser.blogspot.co.uk/2009/09/cpu-operation.html

[5] Input Process Output. (n.d.). Retrieved December 6, 2014, from

http://ict.stmargaretsacademy.org.uk/computing/hardware/ipo.html

[6] Inman, K., & Fritsky, L. (2014, December 1). What is an address bus. Retrieved December 6, 2014, from

http://www.wisegeek.com/what-is-an-address-bus.htm

[7] Husted, H. (2014, November 29). What Is a Data Bus? Retrieved December 7, 2014, from

http://www.wisegeek.org/what-is-a-data-bus.htm

[8] Lanz, C., & Wiley, M. (2014, December 3). What is a Control Bus? Retrieved December 7, 2014, from

http://www.wisegeek.com/what-is-a-control-bus.htm#didyouknowout

[9] Covington, M. (2004, January 1). PIC Assembly Language for the Complete Beginner. Retrieved December

9, 2014, from http://www.covingtoninnovations.com/noppp/picassem2004.pdf

[10] Microchip PIC16F84 Data Sheet. (2001, January 1). Retrieved December 9, 2014, from

http://ww1.microchip.com/downloads/en/DeviceDoc/35007b.pdf

[11] Book: PIC Microcontrollers. (n.d.). Retrieved December 9, 2014, from

http://www.mikroe.com/chapters/view/5/chapter-4-timers/)./

[12] PIC Instructions. (n.d.). Retrieved December 9, 2014, from http://tutor.al-williams.com/pic-inst.html

[14] Difference between Microprocessor and Microcontroller. (n.d.). Retrieved December 10, 2014, from

http://ww1.microchip.com/downloads/en/DeviceDoc/35007b.pdf

40 | P a g e

http://www.zseries.in/embedded lab/8051 microcontroller/difference between microprocessor and

microcontroller.php#.VK7fGCusVGl

[15] RAM & ROM. (n.d.). Retrieved January 29, 2015, from http://www.diffen.com/difference/RAM_vs_ROM

[16] Z. S. (n.d.). VN2222LL. Retrieved January 28, 2015, from Datasheet Catalog - datasheetcatalog.com :

http://pdf.datasheetcatalog.com/datasheet/zetexsemiconductors/vn2222ll.pdf

[17] D. W. (2002). PIC In Practice: A Project Approach. Oxford: Newnes.

[18] M. (n.d.). Maplin electrical components. Retrieved February 3, 2015, from The electronics specialist -

Maplin: http://www.maplin.co.uk/search?text=electrical+components&x=0&y=0

[19] L. D. (n.d.). Sparkfun - LM7805 Datasheet. Retrieved February 25, 2015, from Sparkfun:

https://www.sparkfun.com/datasheets/Components/LM7805.pdf

Images Ref:

Figure 1 –

[1] Electronic Circuits and Diagram (2013, October 23). Retrieved December 8, 2014, from

http://www.circuitstoday.com/microcontroller-invention-history

Figure 2 –

[13] Google images – Different microcontrollers in various applications

https://www.google.co.uk/search?q=microcontrollers&espv=2&biw=1242&bih=606&source

=lnms&tbm=isch&sa=X&ei=DKyAVLvMNJCR7AaN-IDwBQ&ved=0CAYQ_AUoAQ

Figure 2 (ii) –

[15] Google images – Devices using microcontrollers

https://www.google.co.uk/search?q=microcontrollers+used+in+a+variety+of+devices&espv

=2&biw=1366&bih=667&source=lnms&tbm=isch&sa=X&ei=V2jkVL__C8OC7gbwvICIBQ&ved

=0CAcQ_AUoAg#tbm=isch&q=devices+using+microcontrollers+&imgdii=_.

The rest of the images were obtained from articles and websites, carrying its own reference

from bibliography list.

#Kind regards

http://www.circuitstoday.com/microcontroller-invention-history

https://www.google.co.uk/search?q=microcontrollers&espv=2&biw=1242&bih=606&source=lnms&tbm=isch&sa=X&ei=DKyAVLvMNJCR7AaN-IDwBQ&ved=0CAYQ_AUoAQ

https://www.google.co.uk/search?q=microcontrollers&espv=2&biw=1242&bih=606&source=lnms&tbm=isch&sa=X&ei=DKyAVLvMNJCR7AaN-IDwBQ&ved=0CAYQ_AUoAQ

41 | P a g e

Chapter VIII - Appendix

Appendices

Appendix 1 – PIC detailed block diagram

[2]

Appendix 2 – Instruction set

42 | P a g e

Appendix 3 – Complete Program

;====================================================================

; Main.asm file generated by New Project wizard

;

; Created: Tue Nov 18 2014

; Processor: PIC16F84A

; Compiler: MPASM (MPLAB)

;Product name: LED on/off with 0.5 sec delay

;Jordan Lee Mauro Buhagiar

;Date: 18/11/2014

;version:1.0

;====================================================================

;====================================================================

; DEFINITIONS

;====================================================================

#include p16f84a.inc ; Include register definition file

;use delay(clock=4MHz) ;defines oscillator

;fusesxt, nowatt, noprotect, noput

;xt oscillator, no watchdog time

;no code protection, no power up timer

;byte portb=6 ;defines memory location

;================================================================

; VARIABLES

;================================================================

; RESET and INTERRUPT VECTORS

;================================================================

; CODE SEGMENT

43 | P a g e

;================================================================

PGM code

Start

;=============================================================== ;Equates Section

;================================================================

TMR0 equ 1 ;TMR0 is address 1

STATUS equ 3 ; STATUS is address 3

PORTA equ 5 ; PORTA is address 5

PORTB equ 6 ; PORTB is address 6

TRISA equ 85h ; " " " 85h

TRISB equ 86h ; " " " 86h

OPTION_REG equ 81h ; " " " 81h

ZERO_BIT equ 2 ; " " " 2

COUNT equ 0CH ; File 0C = COUNT, a Reg that counts

events

;================================================================

ORG 0 ;Start at address 0

GOTO START

;================================================================

;Configuration Bits

__CONFIG H'3FF0' ;Selects LP Oscillator, Watch Dog Timer -

OFF, PUT on

;CODE protection disabled

;================================================================

;SUBROUTINE SECTION

DELAY56

MOVLW .112 ;Time 112 (30 seconds * 112 =3360

/60mins = 56mins delay

44 | P a g e









RETLW 0 ;Time is now zero = 56 minute, time to

execute

FOUR_MINS_DELAY

MOVLW .8 ;Time .8 (8 * 30 seconds[1/2]= 4 mins)

MOVWF COUNT ;Store value .8 in count

LOOP2 CALL DELAY6 ;wait 6 second





DECFSZ COUNT ;decrementing by 1 from count

GOTO LOOP2 ;Still not Zero

RETLW 0 ;Time is now Zero = 4mins, time to execute






RETLW 0 ;Time is 192 = 6sec,Return

;================================================================

;CONFIG SECTION

START

45 | P a g e

BSF STATUS,5 ;Turns to bank1

MOVLW B'00011111' ;5 bits PORTA as inputs

MOVWF TRISA ;Inputs are defined as TRISA


MOVWF TRISB ;Outputs are defiend as TRISB

MOVLW B'00000111' ;Prescaler is /256








CALL DELAY56 ;wait 56mins 1ST HOUR Delay


CALL DELAY56 ;wait 56mins 2ND HOUR


CALL DELAY56 ;wait 56mins 3RD HOUR


CALL DELAY56 ;wait 56mins 4TH HOUR






;================================================================

END

46 | P a g e

Appendix 4 – Program Flow Chart

START

Delay 56(Mins)

Set LED on

Delay 4(Mins)

Call Delay 4(Mins)

Sub Routines

Set LED Off

Call Delay 56(Mins)

1 Hour Delay Achieved with LED

operating for 4 mins

Call Delay 4 and Delay 56, 4 more times in series to

make 6 Hours delay and repeat Cycle

Call Delay 4(Mins)

Call Delay 56(Mins)

1 hour Delay achieved, LED still

off

At this point LED has operated for 4 minutes & 6 hours

delay has been achieved. & Repeats

Documents

Embedded Microcontrollers LED Based Program Design