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UNIVERSITY OF NAIROBI

FACULTY OF ENGINEERING

DEPARTMENT OF ELECTRICAL AND INFORMATION ENGINEERING

PROJECT: A MICROCONTROLLER BASED WIRELESS E-NOTICE BOARD

PROJECT INDEX: 06

NAME: LUBANGA DENNIS WASIOYA

REG. NO: F17/1353/2010

SUPERVISOR: PROF. ELIJAH MWANGI

EXAMINER: MR. C. OMBURA

A project report submitted to the Department of Electrical and Information Engineering in

partial fulfillment of the requirements for the award of the Degree of Bachelor of Science

in Electrical and Electronic Engineering of the University of Nairobi

Submitted on: 24TH

APRIL 2015

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DECLARATION OF ORIGINALITY

NAME: LUBANGA DENNIS WASIOYA

REGISTRATION NUMBER: F17/1353/2010

COLLEGE: College Of Architecture and Engineering

FACULTY: Engineering

DEPARTMENT: Electrical and Information Engineering

COURSE: Bachelor of Science in Electrical and Electronic

Engineering

PROJECT NAME: A Microcontroller Based Wireless E-Notice Board

1. I understand what plagiarism is and I am aware of the university policy in this regard.

2. I declare that this final year project report is my original work and has not been submitted

elsewhere for examination, award of a degree or publication. Where other people’s work

or my own work has been used, this has properly been acknowledged and referenced in

accordance with the University of Nairobi’s requirements.

3. I have not sought or used the services of any professional agencies to produce this work.

4. I have not allowed, and shall not allow anyone to copy my work with the intention of

passing it off as his/her own work.

5. I understand that any false claim in respect of this work shall result in disciplinary action,

in accordance with University anti-plagiarism policy.

Signature:………………………………………….

Date:………………………………… ………….

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DEDICATION

This project is dedicated to my dad, who financially and emotionally supported me through my

entire academic life, and my mom for being there for me always.

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ACKNOWLEDGEMENT

First of all, I would like to sincerely express my gratitude to the almighty God who gave me life,

strength and opportunity to get this far in my academic life.

I would also like to thank my supervisor, Prof. Elijah Mwangi, for his insight and valuable

assistance he provided me to make this project work.

I also express my gratitude to the department and especially the electronics laboratory

technicians for the assistance they gave me in completion of my project.

Lastly, I would like to thank my friends and classmates for their educational and any other

related insight they afforded me during the period I was undertaking this project.

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ABSTRACT

Notice boards are vital in all institutions as they are used to relay vital information to all the

concerned persons in the given institution. They are also common with advertising agencies. The

GSM based electronic notice board discussed in this paper presents a way to do away with paper

base notices. The GSM notice board enables notices to be posted without the authorized person

being physically at the location of the board as the notices are sent as text messages. The GSM E

notice board can set to only gives authorized access to the board so that the content going to the

board is controlled.

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TABLE OF CONTENTS

DECLARATION OF ORIGINALITY ........................................................................................ I

DEDICATION.............................................................................................................................. II

ACKNOWLEDGEMENT .......................................................................................................... III

ABSTRACT ................................................................................................................................. IV

TABLE OF CONTENTS ............................................................................................................ V

ABBREVIATIONS AND ACRONYMS ................................................................................. VII

LIST OF FIGURES ................................................................................................................. VIII

LIST OF TABLES ...................................................................................................................... IX

CHAPTER 1 .................................................................................................................................. 1

INTRODUCTION......................................................................................................................... 1

1.1 BACKGROUND ........................................................................................................................ 1

1.2 PROBLEM STATEMENT ........................................................................................................... 1

1.3 OBJECTIVES ........................................................................................................................... 1

1.4 SCOPE OF WORK .................................................................................................................... 2

1.5 ORGANISATION OF THE PROJECT ............................................................................................ 2

CHAPTER 2 .................................................................................................................................. 3

LITERATURE REVIEW ............................................................................................................ 3

2.1 THE MICROCONTROLLER ....................................................................................................... 3

2.1.1 Classification of microcontrollers .................................................................................. 3

2.1.2 Applications of Microcontrollers ................................................................................... 6

2.1.3 The PIC 16F690 ............................................................................................................. 6

2.2 GSM MODEM ...................................................................................................................... 9

2.3 DISPLAY UNIT ...................................................................................................................... 10

2.3.1 Classification of LCD’s ............................................................................................... 11

2.4 POWER SUPPLY .................................................................................................................... 12

2.5 PROGRAMMING LANGUAGE AND SOFTWARE ....................................................................... 12

2.5.1 Programming Language ............................................................................................... 12

2.5.2 Tools and Computer Software ..................................................................................... 13

CHAPTER 3 ................................................................................................................................ 15

DESIGN AND IMPLEMENTATION ...................................................................................... 15

3.1 SOFTWARE DESIGN .............................................................................................................. 15

3.1.1 The Microcontroller Unit ............................................................................................. 16

3.1.2 LCD Screen .................................................................................................................. 17

3.1.4 Computer Software Used ............................................................................................. 21

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3.2 HARDWARE IMPLEMENTATION ............................................................................................ 22

3.2.1 LCD Connections......................................................................................................... 22

3.2.2 GSM connections ......................................................................................................... 23

3.2.3 PIC connections ........................................................................................................... 24

3.2.4 The Power Supply Unit ................................................................................................ 25

CHAPTER 4 ................................................................................................................................ 26

RESULTS AND ANALYSIS ..................................................................................................... 26

4.1 STARTUP DISPLAY ............................................................................................................... 26

4.2 GSM MESSAGE DISPLAY ..................................................................................................... 27

CHAPTER 5 ................................................................................................................................ 28

CONCLUSION AND RECOMMENDATIONS ...................................................................... 28

5.1 CONCLUSIONS ...................................................................................................................... 28

5.2 REALIZATION ON LARGER SCREEN ....................................................................................... 28

5.3 RECOMMENDATIONS ............................................................................................................ 29

BIBLIOGRAPHY ....................................................................................................................... 31

APPENDIX .................................................................................................................................. 33

A. MICROCONTROLLER CODE ................................................................................................. 33

B. PIC16F690 INTERNAL ARCHITECTURE .............................................................................. 41

C. CIRCUIT DIAGRAM ................................................................................................................ 42

D. COST OF MATERIALS ............................................................................................................. 43

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ABBREVIATIONS AND ACRONYMS

GSM Global System of Mobile

SIM Subscriber Identification Module

PIC Peripheral interface Control

LCD Liquid Crystal Display

LED Light Emitting Diode

TFT Thin Film Transistor

RX receiver

TX Transmitter

GND Ground

ALU Arithmetic and Logic Unit

CISC Complex Instruction Set Computing

RISC Reduced Instruction Set Computing

PC Personal Computer

IDE Integrated development Environment

ASCII American Standard Code for Information Interchange

ETSI European Telecommunications standards Institute

2G Second Generation

EEPROM Electrically Erasable Programmable Read Only Memory

ROM Read only Memory

ISR Interrupt Service Routine

USART Universal Synchronous Asynchronous Receiver Transmitter

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LIST OF FIGURES

Figure 2. 1 Types of Microcontrollers ............................................................................................ 3

Figure 2. 2 Transmitting data using USART module [3] ............................................................... 8

Figure 2. 3 The GSM MODEM .................................................................................................... 10

Figure 2. 4 Internal structure of the LCD screen .......................................................................... 10

Figure 2. 5 A 20 by 4 LCD screen ................................................................................................ 12

Figure 2. 6 Pickit 3 ........................................................................................................................ 14

Figure 3. 1 Software design flowchart .......................................................................................... 15

Figure 3. 2 The STATUS register [9] ........................................................................................... 16

Figure 3. 3The OSCCON register [9] ........................................................................................... 19

Figure 3. 4 The INTCON Register [9] .......................................................................................... 20

Figure 3. 5 The PIE1 Register [9] ................................................................................................. 21

Figure 3. 6 Block Diagram of the Project ..................................................................................... 22

Figure 3. 7 Level Shifter Circuit [12] ........................................................................................... 24

Figure 3. 8 Pin Diagram of the Microcontroller [2] ...................................................................... 24

Figure 3. 9 Voltage Stabilizer Circuit [6] ..................................................................................... 25

Figure 4. 1 Proteus Simulation...................................................................................................... 26

Figure 4. 2 Practical Result ........................................................................................................... 26

Appendix Figure 1. 1 Internal Architecture of PIC16F690 [3] .................................................... 41

Appendix Figure 1. 2 Proteus Circuit Diagram ............................................................................ 41

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LIST OF TABLES

Table 3. 1: Bank Selection ............................................................................................................ 17

Table 3. 2: LCD Instructions ........................................................................................................ 18

Table 3. 3: Internal Clock setting .................................................................................................. 19

Table 3. 4: Baud Rate setting [12] ................................................................................................ 20

Table 3. 5: LCD pin Connections ................................................................................................. 23

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CHAPTER 1

INTRODUCTION

1.1 Background

Microcontrollers have become an integral part of modern systems as they provide the ability to

create stand alone systems which have revolutionize the technological world. The ability to

program microcontrollers to perform a given task under a certain circumstance and react

differently in another situation has made our work easier in many ways. In order to create any

system, a microcontroller is interfaced with several peripheral devices depending on what the

system designer wants to create. For example, to create a notice board as in this project, a display

unit and a GSM MODEM are connected to the microcontroller. The GSM MODEM is

responsible for the reception of the notices and sends the information to the microcontroller

which in turn sends the message to the display unit [1].

This is just one example of the systems that can be actualized by connecting a microcontroller to

some other devices. There are many systems that can be made using microcontrollers. This

project discusses the making of a wireless notice board and explains how it can be implemented

on a larger and economically viable way.

1.2 Problem Statement

A notice board is an important item in any institution as it is used to pass any information to

people in the institution. They are also very important in the advertising field as companies

market their products and services on these boards. All along, the notice boards have been

“physical” with the notices printed on a piece of paper and posted on the boards. The wireless E

notice board provides the unique opportunity of posting notices remotely from any location in

the world provided there area has GSM network coverage. However, notice boards can distract

motorists on the roads and lead to accidents. It is therefore important to regulate the information

one puts on these boards so as to ensure they are less distractive.

1.3 Objectives

The objectives of this project is to design a GSM E-Notice board based on the PIC

microcontroller that will have the following functionalities;

Receive a text message sent through the GSM network

Display the message on a LCD screen

Discuss how the project can be realized using the more economically practical TFT LCD

and LED screens

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1.4 Scope of Work

The project covers the following areas;

Using a PIC microcontroller to display text on an LCD screen

Connecting a GSM MODEM to a microcontroller and receive text messages from a

mobile phone through the GSM Network

If the received text is from an authorized source, display the text on the LCD screen, if

not authorized, discard the text message

The other functionalities of the GSM MODEM such as receiving calls and checking the signal

strength of the GSM network are not within the scope of this project

1.5 Organisation of the Project

The project is organized into five chapters as follows: the introduction, the literature review,

design and implementation, results then the conclusions and recommendations. After the

chapters there are the references and lastly the appendix.

The introduction to the project discusses the background of the project, problem statement,

objectives and the project scope.

The literature review section is where the various components of the project are discussed. These

components include the GSM MODEM, the microcontroller, the power supply and also the

programming language and the software used.

The design and implementation chapter focuses on the software and hardware implementation of

the project. The software part discusses how the modules are interfaced in the program code and

the hardware design focuses on the physical creation of the wireless E-Notice board system.

The fourth chapter is where the results of the project are presented and their analysis given. The

results of the project are divided into; simulated and practical. The simulated results are seen

from the software in the PC and the practical results are seen on the Breadboard from actual

circuitry.

The fifth chapter concludes the findings of the entire project and recommends what should be

done for further works in line with that project.

References of the project are given after the fifth chapter. The appendix has the MCU code used,

the circuit diagram, important figures and the breakdown of the project cost.

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CHAPTER 2

LITERATURE REVIEW

This chapter discusses the various components and aspects that have been used in this project.

These are the microcontroller, the LCD screen, the GSM/GPRS MODEM, the power supply,

software and other tools used.

2.1 The Microcontroller

By definition, a microcontroller is simply a computer on a chip. To be able to produce any

system, like a GSM E-Notice board, several peripheral devices are to be interfaced with the

microcontroller and a code is programmed into the microcontroller to enable the peripherals to

work in a certain way so that the system is complete [2]. The microcontrollers are of different

types and they are classified in different ways.

2.1.1 Classification of microcontrollers

Microcontrollers can be classified into many types based of various aspects some of them being;

bus width, instruction set, memory architecture, instruction set and family. Here we shall look at

all these classification aspects with special reference to the PIC 16F690. Figure 2.1 shows one

way of classifying microcontrollers.

Figure 2. 1 Types of Microcontrollers [1]

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2.1.1.1 Memory Architecture

Architecture is the conceptual design and operational structure of the microcontroller. There are

two main architectural designs which are considered to classify any microcontroller, the Von

Neumann and the Harvard architectures. The two architectural designs differ in the way data and

programs are accessed and stored.

2.1.1.1.1 Harvard Architecture

In this memory architecture, the program memory is completely separated from the data

memory. All PIC microcontrollers have the Harvard architecture. With the separate physical

memories, each memory has its special dedicated bus used for instruction and data flow. This

allows faster execution of commands and parallel flow of data is possible [2].

2.1.1.1.2 Von Neumann Architecture

In this design, the controller can either read an instruction or write one but not read and write at

the same time as the two processes use a single bus for instruction and data transfer. The

advantage of the von Neumann architecture is that it can handle both a program with very large

program memory requirements but little data space or one with very little program memory

requirement with very large data amount without any problem. It is also able to optimize

memory for both cases.

The architecture, however, has many disadvantages thus making it not very common among the

microcontrollers. First, since the memory is the same for the entire chip, if you happen to

misplace the place holder of the instruction to be executed next your computer may “hang”.

Also, some program data may be moved to the next memory location if it doesn’t fit in the

desired destination. This next location can contain data from another program and hence this will

intentionally overrun the data memory with program instructions [2].

2.1.1.2 Bus Width

Classifications according to the width of the internal data bus of the microcontroller lead to the

following types:

2.1.1.2.1 8-bit Microcontroller

A microcontroller is regarded as an 8-bit microcontroller when the ALU performs its operations

on a byte at an instruction. This simply means that the internal bus width is 8-bit long. Examples

of 8-bit microcontrollers are Intel 8051 family and Motorola MC68HC11 family. The

PIC16F690 microcontroller which is used in this project falls under this category.

2.1.1.2.2 16-bit microcontroller

The data bus width of this family of microcontrollers is 16- bit as the names suggest. Examples

of 16-bit microcontrollers are Intel 8096 family and Motorola MC68HC12 and MC68332

families. The capabilities of this microcontroller family are greatly improved as compared to the

earlier family.

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2.1.1.2.3 32-bit microcontroller

As the name suggest, the internal bus width is 32 bits long. Examples of this family are the Intel

80960 family and Motorola M683xx and Intel/Atmel 251 family Again their capabilities greatly

surpass those of the 16 bit bus width.

2.1.1.3 Instruction Set

Classification made taking into account the instruction sets, results in three distinct types of

microcontrollers i.e. CISC, RISC and SISC.

2.1.1.3.1 CISC

This is an acronym for Complex Instruction Set Computing. This architecture contains a large set

of instruction ranging from very complex to very simple. The disadvantage of the CISC

architecture is that it is easier to compute these complex computations by using short instructions

instead of the complex ones making the CISC architecture inefficient. This led to the

development of the RISC to efficiently work out the inefficiencies of the CISC. Examples of

systems with this architecture are the Intel Pentium processors [2].

2.1.1.3.2 RISC

RISC architecture, which stands for the Reduced Instruction Set computer, uses a small, highly

organized set of instructions as opposed to the complex instructions used by the CISC

architecture. This now the most common architecture used in microcontrollers [2].

Another possible architecture based on the instruction set is the SISC architecture which stands

for Special Instruction Set Computing. This type is not as common as the other two.

2.1.1.4 Memory Devices

This classification yields two types of microcontrollers; embedded memory microcontroller and

external memory microcontroller

2.1.1.4.1 Embedded Memory

This is a microcontroller which has all the functional blocks available on a chip. These functional

blocks are the data memory, I/O ports, Serial communication, counters and timers as well as

interrupts.

2.1.1.4.2 External Memory

Not all the functional blocks are available on the same chip. An example of such is the Intel 8031

where the program memory is not available on the chip and hence an external memory has to be

connected.

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Microcontrollers can also be classified by the family which is based on the manufacturer of the

microcontroller leading to a number of microcontroller types. The main types are AVR and PIC.

PIC,made by Microchip, is used in this project

2.1.2 Applications of Microcontrollers

Microcontrollers are vital in the building of various devices across the technological divide. The

applications of the microcontroller include:

Light sensing and control devices

Temperature sensing and control devices

Fire detection and safety devices

Industrial instrumentation devices

Process control devices

Voltage, current and power measurement

Measuring revolving objects

Hand held metering systems

Among many other applications

2.1.3 The PIC 16F690

The PIC 16F690 is a 20 pin microcontroller. This PIC belongs to the 16 series 8-bit mid-range

class of PIC microcontrollers with a typical range of interfaces which includes;

Digital input/output

Analog inputs (12 pins)

Multimode timers (3)

Serial ports

An internal clock (4MHz)

The chip has 4K of program memory, 256 bytes of SRAM and another 256 bytes of

EEPROM.The chip can be initialized to provide 18 I/O pins and the other two are for VDD and

VSS. The 18 pins are grouped into three ports, A (6pins), B (4 pins) and C (8 pins) [3].

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Other important features of the PIC16 F690 that are instrumental in the construction of the E-

Notice board are;

Serial ports (mostly the USART)

Interrupts

EEPROM Data Memory

2.1.3.1 Serial Ports

Serial ports allow the PIC to communicate with a wide range of other devices; in our case we

want the microcontroller to communicate with the LCDs and the GSM MODEM so as to send

messages to the Notice Board. The USART stands for Universal Synchronous/Asynchronous

Receiver/Transmitter. The use of the USART involves sending or receiving an 8-bit or 9-bit

packet of data i.e. a byte of data plus a parity bit where the parity bit is used for error checking

the byte sent. The error checking mechanism works such that if there are an odd number of ones

in the data byte sent or received then the parity bit will be 1 and if the number of 1s is even then

the parity bit will be 0. If there is an error in the sent or received data then the parity bits of the

two will not match and hence the receiver will detect an error [4].

The USART module has two modes of operation i.e. asynchronous operation and synchronous

operation.

In Asynchronous operation, the RX pin of the PIC microcontroller is connected to the TX pin of

the device (in our case the GSM MODEM) and the data is swapped. This connection is referred

to as Full Duplex connection.

In synchronous operation, clock and data lines are shared between a number of devices with the

master device responsible for providing the clock.

In both these modes, the rate at which data is sent by the transmitter should be equal to the rate at

which the receiver expects the same data. This rate is known as the Baud Rate, which for this

project is set at 9600. The baud rate is set using register SPBRG which is located in Bank 1.

In the PIC microcontrollers, the registers responsible for receiving and transmission of data are

the RCSTA (located in Bank 0) and the TXSTA (located in Bank 1). Data read is stored in the

RCREG register (located in Bank 1) whereas data to be transmitted is stored in the TXREG

register also in Bank 1

When the USART is to send data (8 OR 9- Bits long) the module adds a start bit (usually a 0) to

the front of the data to be sent and a stop bit (usually a 1) to the end of the data resulting in a 10

or 11-bit long data. This is then moved to the shift register which rotates the bits onto the

transmission pin (TX).

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This is shown on the figure below:

Figure 2. 2 Transmitting data using USART module [4]

The receiver module will constantly check the state of the RX pin to see if any data is received.

The RX pin is normally HIGH and the start bit of the sent data is a LOW. If the RX pin goes

LOW, this means the sent data has reached the RX pin. Three samples are taken in the middle of

the bit to ensure it really is the start bit then other samples of the subsequent bits are taken with

three samples in the middle of each bit. The timing of the sampling is dictated by the Baud Rate

of the devices. The stop bit must read a ‘1’ otherwise the data is declared a “Badly Framed” and

an error is registered.

When a HyperTerminal (like the GSM MODEM) is connected to the serial port, whatever

character is entered is sent as ASCII through the serial port. These characters can then be

displayed on the LCD.

Both modes (Synchronous and Asynchronous) support a feature called the Address Detect which

allows a number of devices to be connected to the PIC. In order to transmit, an address byte must

first be sent out to identify the intended recipient [4].

2.1.3.2 Interrupts

An interrupt is an externally or internally generated signal which forces the processor to suspend

its current operation and execute the Interrupt Service Routine (ISR). This is because the ISR is

given a higher priority than the background processes. In the programming of the E-Notice

board, an incoming message is viewed as an interrupt. Once the message is received, the

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processor leaves whatever it was doing, displays the message if it is from an authorized source or

discards the message if the source is not authorized [5].

2.1.3.3 EEPROM Data Memory

The EEPROM is a collection of General Purpose file registers whose contents remain intact even

when power to the microcontroller is cut off. Information that is vital to the functioning of a

system like the passwords and authorized phone numbers are stored in the EEPROM.

The file register EEADR (located in Bank 3) holds the address in the EEPROM which you wish

to read from or writes to while EEDATA file register holds the data you have just read or wish to

write in the EEPROM. The writing process involves the use of registers EECON1 and EECON2,

both of which are located in Bank 3. EECON1 is used to hold setting of the EEPROM whereas

the EECON2 is a special function register used in the EEPROM writing process.

In the creating of the Notice board, it is important that only authorized persons get to display

notices on the board. The EEPROM is important to this function as the programmer gets to give

certain users this opportunity by storing their phone numbers in the EEPROM. As mentioned

earlier the EEPROM memory for the PIC 16F690 is 256 bytes [5].

2.2 GSM MODEM

GSM, acronym for the Global System of Mobile Communication, are standards set by the

European Telecommunications Standard Institute (ETSI) to describe the protocols of the 2G

digital cellular networks used for mobile phones. By the year 2014, the GSM network was the

default mobile communication system in the world with over 90% of the market share for mobile

communication which translates to coverage in 219 countries and territories. Since the GSM

network covers our entire country, a GSM MODEM will be appropriate for use in this project.

The GSM MODEM is a specialized MODEM that accepts a SIM card and operates via

subscription to a mobile operator just like a mobile phone. The SIM card used in the GSM

MODEM is from the wireless carriers such as Safaricom, Airtel or Orange. The GSM MODEM

has the following capabilities when used in a system;

Reading, writing and deleting of messages

Sending of text messages

Monitoring the signal strength

Reading writing and searching entries in the phonebook

The GSM MODEM used in this project is the SIM 900 Mini Wireless Data Transmission

Module GSM/GPRS board kit w/Antenna.

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The figure 2.3 below shows the GSM MODEM that will be used in this project

Figure 2. 3 The GSM MODEM [6]

2.3 Display Unit

In this project, the display of the messages/notices is handled by the LCD, an acronym that

stands for Liquid Crystal Display. The LCD screen is an output device which enables the

messages or notice to be displayed for the intended audience to see it. The display on the screen

can be ASCII characters or dot based graphics depending on the message to be displayed.

The LCD screen is made up of a layer of pneumatic crystals sandwiched between two layers

polarized glass with a perpendicular axis of polarity. The angle of light vibration determines the

amount of light that passes through the layers and hence the characters displayed on the LCD.

Figure 2.4 shows the internal Structure of the LCD screen

Figure 2. 4 Internal structure of the LCD screen [7]

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The electric current supplied to the LCD affect the angle of twist of the liquid crystal hence the

amount of light that passes through the LCD. This is how the display of the different characters

is achieved using the LCD screen.

2.3.1 Classification of LCD’s

There are three criteria with which LCDs are classified by with each criterion resulting in several

types of LCDs.

2.3.1.1 According to how they are illuminated

LCDs can be illuminated either from the back, from an external source or from a combination of

the two methods

When the pixels of the LCDs are illuminated from behind the monitor screen and the LCD is

viewed from the front then the LCD is said to be transmissive. Transmissive LCDs are common

in appliances which require high level illumination such as laptop computers and television sets.

When the pixels are illuminated from the front of the screen, the same side as the user is said to

be a reflective LCD. This type of LCD is suitable for low power consumption applications and is

therefore common in digital watches and calculators. This is the type of LCD which is used in

this project.

When the pixels can either be illuminated from the front or from the back of the screen then the

LCD is said to be transflective. The term transflective is used to show that this particular LCD is

a combination of both the transmissive and the reflective LCDs. This LCD works either as a

reflective or a transmissive LCD depending on the ambient lighting available.

2.3.1.2 Colour or Monochrome LCDs

In the color LCDs, each pixel contains cells which are red, green or blue. A pixel can have sub

pixels each of which contain the three colors which are independently controlled and as a result

the LCD is capable of showing millions of colors for each pixel

The monochrome LCD is the most commonly used with microcontrollers

2.3.1.3 According to Display Technology

Basic on this criterion, LCDs are either alphanumeric or dot addressable. There are three

electrode configuration used for this display using the LCD.

The alphanumeric type, which uses a matrix composed of linear segments, is most common in

microcontroller applications. The seven and sixteen segment electrode configurations as shown

below are suitable for small digital devices such as watches and calculators.

The dot addressable type is necessary when there is need to display an entire character or for

graphical display. This type of LCD has more addressable elements hence its more complex that

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the earlier mentioned LCD. The matrix format LCD display is the most common in

microcontroller circuits.

The LCD that is used for this project is LCD screen which is shown in Figure 2.5

Figure 2. 5 A 20 by 4 LCD screen [7]

2.4 Power Supply

The PIC16F690 used in this project requires a constant +5V voltage to operate and this is

supplied by the mains supply. An adapter converts the 240V ac into a 12V dc which is then

passed through a voltage regulator circuit to produce a stable 5V dc supply suitable for the

working of this project [8] [9].

2.5 Programming Language and Software

This section is divided into two parts; programming language used and the tools/computer

software used in the project development.

2.5.1 Programming Language

A programming language is a constructed language designed to communicate instructions to a

machine. They are used to create programs that control how a machine functions in different

circumstances. This project is done in assembler language. This is a low level programming

language for a microcontroller or other programmable device. The assembler language has a very

strong association with the architecture of the microcontroller hence a good understanding of the

microprocessor architecture is required when programming using assembler [10].

Programming in assembler language has the following advantages:

Requires less memory and execution time.

Allows hardware specific complex jobs easier

Suits time sensitive jobs

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2.5.2 Tools and Computer Software

These are the hardware and computer software used during the project in various sections of

building the prototype and the eventual finished project. The tool used is the Pickit 3 whereas the

software programs used are MPLAB and Proteus.

2.5.2.1 MPLAB

This is software, developed by Microchip, which gives a platform for the writing and debugging

of the assembler language. The MPLAB software is furnished with an IDE which allows the user

to develop software of embedded systems. Software for an embedded system is referred to as

firmware as it cannot be easily changed and requires special equipment i.e. the programmer to

put it on the system it was designed for. The only disadvantage of the MPLAB software is that it

was designed PC. A user on Mac, UNIX or Linux systems cannot use MPLAB. This is however

not a problem to us because the project was done on a PC [12].

2.5.2.2 Proteus

Proteus is simulation software which enables us to see if the code that has been written serves the

intended purpose. The Proteus software enables us to draw the circuit of the particular project

including all the passive and active components required to make the circuit work. The code for

the particular section is input and when the circuit is run, experimental results of the project are

obtained. The only disadvantage of using Proteus is that it assumes all the components are ideal

and hence the experimental results are not necessary the same as the practical ones. This force

the designer to be as close as possible to the experimental results hence a good quality product is

obtained [12].

2.5.2.3 Programmer

Relating to microcontroller technology, the process by which a program is transferred to a chip is

called burning or blowing the chip. A device that burns a program onto a chip is called a

programmer. A programmer contains the following components:

A software package to run on a PC

A cable connecting the PC to the programmer

A programmer device

In this project the Pickit 3, which is designed specifically for MPLAB and the PIC

microcontrollers, was used.

14

A photo of the Pickit 3 with its accessories is shown in figure 2.6

Figure 2. 6 Pickit 3 [11]

15

CHAPTER 3

DESIGN AND IMPLEMENTATION

This section discusses how the wireless Electronic Notice board was designed and implemented

using the PIC 16F690. The section is broken down into the:

Software module.

Hardware module.

3.1 Software Design

Software design involves the use of software in the development of the project. The flowchart

shown in figure 3.1 outlines the software design procedure that was used to develop this system

Figure 3. 1 Software design flowchart

16

Software design was divided into four parts namely; the Microcontroller Unit, the LCD screen,

the USART functions and the Computer software used.

3.1.1 The Microcontroller Unit

For a microcontroller to function, it has to be connected to peripheral devices which are

connected to the ports of the microcontroller. The first thing to do in PIC programming is the

initialization of the ports and pin function assignment.

Initializing the ports of the PIC microcontroller is done by the use of two Special Function

Registers (SFRs); TRIS and PORT. Each port contain a number of pins and for the PIC 16F690

there are three ports A, B and C which contain 6, 4 and 8 pins respectively. A pin can be set,

becomes an input, or cleared, becomes an output, depending on what you want to connect to the

microcontroller. The block of code below is responsible for the initializing of PORTC which is

where the LCD Screen is connected:

Bcf STATUS, RP0

Clear PORTC

Bsf STATUS, RP0

Clear TRISC

Bcf STATUS, RP0

In the above piece of code, the first line selects the bank where the register PORTC is found i.e.

Bank0. Clearing the port, done with line two, initializes the port. The third line is responsible for

moving to Bank1 where the TRIS register is found, clearing TRIS means all the pins of port are

outputs (the direction of data is to the LCD), and finally the last line moves back to the default

Bank0. Bits 5 and 6 of the status register are responsible for the bank selection as shown in

figure 3.2.

Figure 3. 2 The STATUS register [12]

17

Using the Status register, the selection of the bank is as shown in the table one below [12]

Table 3. 1: Bank Selection

RP1 RP0 BANK SELECTED

0 0 Bank0

0 1 Bank1

1 0 Bank2

1 1 Bank3

Similar blocks of codes are written for PORTs A and B depending on the function allocated to

each pin. In the project, PORTC has the LCD screen connected in 8-bit mode hence all the 8 pins

of PORT C are used up by the LCD. PORT A has the E and RW pins of the LCD and finally

PORT B is where the GSM MODEM is connected because the TX and RX pins of the

microcontroller are located in this port.

3.1.2 LCD Screen

The LCD is made up of 16 pins which control the working of the unit. There are two pins

(labeled A and K) which are responsible for the backlight of the LCD, 8 data pins, D0 to D7,

which are connected to PORT C and finally 3 control pins which are connected to PORT A.

The working of the LCD makes use three different subroutines, called at different times to

perform different tasks. The first subroutine used is the delay, called before anything else in

order to allow the LCD to settle after power is supplied to the LCD. The other two subroutines

are for sending commands to the LCD and for displaying characters on the screen.

The difference between sending commands and sending data to the LCD is due to the state of the

RS pin of the LCD. When the pin is cleared, commands are sent to the LCD whereas setting the

pin allows data to be transferred to the LCD. The E pin is responsible for latching. The R/W pin

is always cleared as the LCD is only used in this project as an output [13].

18

The following table shows LCD commands and how they are used in the LCD initialization

Process.

Table 3. 2: LCD Instructions

Hex value Binary equivalent Description

0x01 00000001 Clear display

0x38 00111000 Set 8-bit, 4 lines, 5x7 matrix

0x0C 00001100 Display ON, cursor OFF, NO blinking

0x85 10000101 Set first line, Shift 5 spaces to the right

0x0C3 11000011 Second line, shift 3 spaces to the right

0x099 10011001 Third line, Shift 5 spaces to the right

0x0D4 11010100 Forth line, 5 spaces to the right

3.1.3 The USART function

The GSM MODEM is responsible for the reception of data sent via the GSM Network and

converting it to a format which the microcontroller can display via the LCD screen. In the

initialization of this module, PORT B is first initialized, the pins of this port are selected such

that TX is an output and RX is an input, configure the Internal clock then finally the Baud rate is

set [9].

For this project the internal clock is set at 4MHz and this is done by the OSCCON register. The

OSCCON register is made up of 3 frequency selection bits (IRCF2, IRCF1 and IRCF0), 2

frequency status bit (HTS and LTS) and 2 system clock control bits (OSTS and SCS)

19

Figure 3. 3The OSCCON register [12]

The 6th

, 5th

and the 4th

bits are responsible for the calibration of the internal clock and the table

below enables the generation of the binary value stored in the OSCCON register [3] [12].

Table 3. 3: Internal Clock setting

IRCF2 IRCF1 IRCF0 Frequency

1 1 1 8 MHz

1 1 0 4 MHz

1 0 1 2 MHz

1 0 0 1 MHz

0 1 1 0.5 MHz

0 1 0 0.25 MHz

0 0 1 0.125 MHz

0 0 0 0.031 MHz

Bit 0 of the OSCCON register is set to tell the microprocessor that the internal oscillator is used.

The binary value stored in the OSCCON register to effect this configuration is 0110001

The Baud rate for the working of the GSM MODEM is set at 9600 which is standard for USART

functionalities using microcontrollers. The setting of the Baud rate is done by the help of three

SFRs; Transmit Status and Control (TXSTA), Baud Rate Control (BAUDCTL) and Serial Port

Baud Rate Generator (SPBRG). To set the Baud Rate, the SNYC bit of the TXSTA register is

cleared, the BRGH bit and the BRG16 bit both of the BAUDCTL register are set. Using the

value calibrated for the internal clock and the formulae below, the baud rate is set and that value

saved in the SPBRG register.

20

The following equations are used in the calculation and setting of the Baud Rate [3] [12]

Eq. 3.1

Eq. 3.2

Eq. 3.3

Using these formulae and the table below the baud rate of 9600 was set using the decimal value

25 which was sent to the SPBRG register [3] [12].

Table 3. 4: Baud Rate setting [12]

Interrupts are used to receive and display the incoming message on the LCD. The INTCON

register is responsible for the initialization of the ISRs

Figure 3. 4 The INTCON Register [12]

21

Bits 7 (GIE) and bit 6 (PEIE) of the INTCON register are set to enable interrupts from peripheral

devices, in this case the GSM MODEM. Once peripheral interrupts are set, it is necessary to

specify the nature of the interrupt which is done using the PIE1 register.

Figure 3. 5 The PIE1 Register [12]

Setting the fifth bit (RCIE) of the PIE1 register results in any incoming message register as an

interrupt prompting the ISR subroutine to execute. All incoming messages were stored in the

RCSTA which sends them to the RCREG registered and from there the LCD subroutines were

used to send the contents of this register to the Screen.

3.1.4 Computer Software Used

The code for the microcontroller and how the peripherals are connected to each other was

written, cleaned and build in the MPLAB software. In this environment, the code is written either

in assembler or in C because MPLAB has compilers for both these languages. For this project,

only assembler was used and the eventual code was saved as .ASM file which is a file extension

associated with assembler code. When the assembler code is compiled, a Hex file is generated.

The Proteus software is where the simulated circuit is drawn using ideal components. The Hex

file produced from compiling is loaded to the PIC microcontroller and the system is run. Once

the system is run successfully on Proteus, it can now be transferred onto a breadboard.

22

3.2 Hardware Implementation

The block diagram for the hardware implementation is shown in figure 3.6.

Figure 3. 6 Block Diagram of the Project

The hardware section can be subdivided into; the display unit, the GSM MODEM Connections,

the power supply and the microcontroller.

3.2.1 LCD Connections

The data pins of the LCD module are connected to PORT C of the microcontroller whereas the

command lines are connected to PORT A. the R/W pin is grounded because the LCD is always

the output and never an input in this project [14].

23

The exact connections between the LCD and the PIC microcontroller are tabulated here:

Table 3. 5: LCD pin Connections

LCD

Terminal

PIC Terminal

(pin number)

Description

DO RC0 (16) Data pin

D1 RC1 (15) Data pin

D2 RC2 (14) Data pin

D3 RC3 (7) Data pin

D4 RC4 (6) Data pin

D5 RC5 (5) Data pin

D6 RC6 (8) Data pin

D7 RC7 (9) Data pin

RS RA5 (2) Control Pin

E RA1 (19) Control Pin

R/W GND (20) Control pin

VDD 5V (1) Power

VSS GND (20) Power

VO Connected to POT Display contrast Control

A 5V (1) Backlight Control

K GND (20) Backlight Control

3.2.2 GSM connections

The GSM MODEM is connected to PORT B of the microcontroller because the TX and RX pins

of the microcontroller are located in this port. The TX terminal of the GSM MODEM is

connected to the RX pin of the microcontroller. From the TX pin of the GSM MODEM, the

incoming message arrives at the RX pin (pin 12) as a voltage which is about 3V. This voltage is

registered by the microcontroller as logic ‘LOW’ and therefore nothing is received. To correct

24

this, GSM is connected to the PIC through a level shifter circuit which is responsible for raising

the voltage of the incoming voltage to 5V. The level shifter circuit is shown in figure 3.7 below.

Figure 3. 7 Level Shifter Circuit [15]

3.2.3 PIC connections

The pin diagram of the 16F690 is shown in figure 3.8 below

Figure 3. 8 Pin Diagram of the Microcontroller [3]

The pins used in connecting the microcontroller to the peripherals are as described below.

Pins 1 and 20 of the microcontroller are VDD and VSS respectively where the VDD supplies the 5V

required to power the PIC and the VSS is the Ground connection for the PIC.

The data pins of the LCD screen are connected to PORTC of the microcontroller. These pins are

denoted as RC0 to RC7 and their pin numbers are as indicated on the pin diagram of the

25

PIC16F690 shown in figure 3.8. The control pins of the LCD are connected on PORTA of the

microcontroller with E terminal of the LCD connected to pin 18 of the PIC and the RS terminal

connected to pin 2 of the PIC. The R/W terminal of the LCD is grounded because we are always

writing to the LCD and never reading from the screen. The LCD receives its power from the VDD

and the VSS terminals which are connected to pins 1 and 20 respectively.

The GSM MODEM is connected to PORTB of the PIC microcontroller. The microcontroller is

receiving from the GSM MODEM and as a result the TX pin of the MODEM is connected to the

RX pin of the PIC (pin 12).

3.2.4 The Power Supply Unit

The microcontroller and the LCD screen require a stable VDD of 5V so as to operate. The GSM

MODEM on the other hand requires a minimum of 4V and can work with up to 5.5 volts. To

supply the PIC and the LCD, a dc voltage of 12V is passed through a regulator circuit to achieve

a stable output of 5V. The 78L05 regulator circuit shown below is responsible for the stable 5V

output.

Figure 3. 9 Voltage Stabilizer Circuit [9]

This 5V output is used to power both the LCD and the PIC microcontroller. This voltage was

also used in the level shifter circuit as the VDD.

The GSM MODEM has its own voltage regulator circuit which gives out a stable 4V output

suitable for the MODEM.

26

CHAPTER 4

RESULTS AND ANALYSIS

This chapter shows the results of the projects and analysis of the results is also presented. This

section takes a look at the simulated and practical results of the project.

This chapter is divided into three sections; Startup display, GSM general message display and

authorized message display.

4.1 Startup Display

When the notice board is powered the following message is seen

Figure 4. 1 Proteus Simulation

Figure 4. 2 Practical Result

27

The practical result for the first part of this project was as expected and is also consistent with the

simulated result.

4.2 GSM Message Display

When the message “Hello!” is sent from the phone to the number specified by the on the

welcome screen. The results are

The first part of the code is the sender of the text, in this case the number 0725693725, the next

line show the date when the text was sent, the time the text was sent is on the third line then the

sent text is on the last line

28

CHAPTER 5

CONCLUSION AND RECOMMENDATIONS

5.1 Conclusions

This was accomplished with some difficulties especially time and the availability of the

components. The wireless e notice board was implemented using the GSM modem which made

it possible to display texts which were sent from a mobile phone using the GSM network. The

GSM modem does not filter the contents sent to it and hence the displayed message contains the

sender’s number, some at commands and some other information. The phone processors are able

to filter this information so that the displayed text is precisely what the recipient needs to see.

The simulation of the project was achieved using the Proteus software and the GSM messages

were simulated using terminal v.9. It was not possible to simulate the entire project working in

Proteus as the GSM modem is unavailable as a component in Proteus. This explains why the first

part of the results only show a message printed on the screen. The terminal software models the

working of the GSM modem and was therefore used for the second part.

5.2 Realization on larger Screen

To realize this e-notice board on a bigger and more economical TFT screen is another

microcontroller with a higher pin count should to be used. The PIC 16f690 has 18 I/O pins while

a 128 by 64 LCD, which is slightly bigger and has graphic capabilities, has 15 data pins. This

leaves 3 pins which are not enough for the control pins and any other peripherals. For larger

screens more data and control pins are required. With a higher pin count MCU and a larger

screen, a higher level programming language will be required because it will be friendlier to use.

The higher programming language will enable pictures and videos to be displayed. In a higher

level language, picture and video compression is easier than if it was to be done in assembler.

Video and picture compression enables files of large sizes to be sent cheaply and also increase

the processing time of the MCU being used.

29

5.3 Recommendations

With assembler language, the amount of material being sent to the screen from the GSM modem

is a lot and most of it is irrelevant to the target audience. When a higher level language is used

the content can be edited to be precise as possible. The display unit used in this project is a 20 by

4 LCD screen and this does not allow for graphic changes and picture to be displayed. For future

work of a similar project, a bigger screen should be used so display is not limited to text

messages only. 29 the GSM modem has other functionalities that can be used to make the notice

board more functional. For example the GSM modem has the capacity to read and write

messages, delete messages from the SIM card and it can also make and receive calls. Future

works should explore these functions.

30

31

BIBLIOGRAPHY

[1] M. Joshi, "EnTcians," Students of E&TC, 25 July 2013. [Online]. Available: electro-

mate.blogspot.com/2013/07/classification-of-microcontrollers.html. [Accessed 17 February

2015].

[2] T. Wilmhurst, Designing Embedded Systems with PIC Microcontrollers: Principles and

applications, Oxford: Elsevier, 2007.

[3] PIC16F631/677/685/687/689/690 Datasheet, USA: Microchip Technology, 2006.

[4] J. Morton, The PIC microcontroller: Your personal introductory course, Oxford: Jordan

Hill, 2005.

[5] M. Bates, PIC Microcontroller: An introductin to Microelectronics, Oxford: Elsevier, 2011.

[6] "Ali Express," [Online]. Available:

m.aliexpress.com/item/478350901.html?tracelog=storedetail2mobilesitedetail. [Accessed 18

February 2015].

[7] "Electronic Experimental Solutions," [Online]. Available:

www.gravitech.us/20chbllcd.html. [Accessed 17 February 2015].

[8] D. Ibrahim, PIC basic Projects: 30 projects using PICBASIC and PICBASIC PRO, Oxford:

Elservier, 2006.

[9] C. P. Sanchez.J, Microcrontroller Programming; The Microchip PIC, London: CRC Press,

2007.

[10] Michael.A.Covington, PIC Assembly language for the complete beginner, Athens:

Gernsback publications, 1999.

[11] "Ali Express," [Online]. Available:

m.aliexpress.com/item/1988030875.html?tracelog=storedetail2mobilesitedetail. [Accessed

18 February 2015].

[12] M. Verle, PIC Microcontrollers, Mikroelectronika.

[13] "PIC Tutorial Three- LCD modules," Winpicprog, june 2002. [Online]. Available:

www.winpicprog.co.uk/pic_tutorial.htm. [Accessed 12 March 2015].

32

[14] M. Bates, Interfacing PIC microcontrollers: Embedded design by interactive simulation,

Oxford: Elsevier, 2006.

[15] "SIM 900 modules," in SIM 900 datasheet.

[16] D. W. Smith, PIC in Practice: A Project based Approach, oxford: elsevier, 2006.

[17] "saving energy forcomputer monitors," [Online]. Available: www.hk-

phy.org/energy/commercial office_is03_e.html. [Accessed 17 February 2015].

33

APPENDIX

A. Microcontroller code ;====================================================================

; PROJECT NUMBER: 6

; MICROCONTROLLER BASED ANEMOMETER

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

; CODED BY: Dennis

; REG NO: F17/1353/2010

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

; fuses

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

radix hex

include "P16F690.INC"

__config _CP_OFF & _WDT_OFF & _BOR_ON & _PWRTE_ON &_INTRC_OSC_NOCLKOUT

&_MCLRE_OFF

errorlevel -302;surpress bank error messages

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

; VARIABLE DECLARATIONS

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

CBLOCK 0X20

passcode

Timer

Timer_X

ENDC

ORG 0x0000 ; Programstorage starting at address 0x0000 in program memory

GOTO START

send_lcd:; sending commands to the LCD

movwf PORTC

bcf PORTA,5

bsf PORTA,1

34

bcf PORTA,1

call delay10ms

return

Data_Write:; writing Characters to the lcd

movwf PORTC

bsf PORTA,5

bsf PORTA,1

bcf PORTA,1

call delay10ms

return

One_ms:; delay of one milisecond

movlw 0XF9

movwf Timer

Xms:

movwf Timer_X

LOOPX:

call One_ms

decfsz Timer_X,F

goto LOOPX

return

delay:

movlw 0XFA

call Xms

return

START:

;Initialising the Registers:

clrf PORTA;initialize portA

clrf PORTB;initialize portB

clrf PORTC;initialize portC

clrf STATUS; return to bank 0

35

bsf STATUS,

bcf OPTION_REG,7; pull up resistor are set

clrf TRISB; set port as all zeros

bsf TRISB,5 ;set bit 5 as a 1

; to enable the serial port clear sync bit of TXSTA and set the SPEN bit of

CLRF TRISC ;PORTC set for outputs

clrf TRISA; set pins port as output

banksel ANSEL ;go to bank 3

clrf ANSEL; set pins as digital

clrf ANSELH;set pins as digital

bcf STATUS,RP0; move back to bank0

;enable interrupts

;set internal oscillator at 8Mhz

bcf STATUS,RP0

bsf STATUS,RP0 ; move to bank 1

movlw b'01100000'; value for setting internal Clock

movwf OSCCON; send set value to OSCCON register

bcf STATUS,RP0;back to bank 0

;Set baud rate at 9600

BSF STATUS, RP0 ;select bank 1

MOVLW d'25' ;9600 baud @ 4 Mhz Fosc +0.16 err

MOVWF SPBRG

MOVLW b'00000100' ;brgh = 1

MOVWF TXSTA ;enable Async Transmission, set brgh

BCF STATUS, RP0 ;select bank 0

MOVLW b'10010000'

MOVWF RCSTA ;enable Async Reception

;LCD SET_UP

CLRF STATUS;BANK0 selected

MOVLW 0X14

36

CALL Xms ;20ms time delay allows LCD to complete initialisation process.

MOVLW 0x01 ;Display clear command

CALL send_lcd

MOVLW 0x38

CALL send_lcd;LCD set for 8-bit, 2-Line,5x8 dot matrix display.

MOVLW 0x0c

CALL send_lcd ;Display on,Cursor off, no Blinking.

MOVLW 0x04

CALL send_lcd

MOVLW 0x01

CALL send_lcd;Display cleared,DDRAM address=0

MOVLW 0x85

CALL send_lcd ;DDRAM address set to 0

;WELCOME message sent to screen

movlw 0x57 ;'w'

call Data_Write

movlw 0x45 ;'E'

call Data_Write

movlw 0x4C ;'L'

call Data_Write

movlw 0x43 ;'C'

call Data_Write

movlw 0x4F ;'O'

call Data_Write

movlw 0x4D ;'M'

call Data_Write

movlw 0x45 ;'E'

call Data_Write

movlw 0x21 ;'!'

call Data_Write

37

Line1:;move to line 2

movlw 0X0C3

call send_lcd

movlw 0X54 ; T

call Data_Write ;

movlw 0X4F ;O

call Data_Write ;

movlw 0X20 ; SPACE

call Data_Write ;

movlw 0X44 ; D

call Data_Write ;

movlw 0X49 ; I

call Data_Write ;

movlw 0X53 ; S

call Data_Write

movlw 0X50 ; P

call Data_Write;

movlw 0X4C ; L

call Data_Write ;

movlw 0X41 ; A

call Data_Write ;

movlw 0X59 ; Y

call Data_Write ;

movlw 0x20 ; Space

call Data_Write

movlw 0x48 ;H

call Data_Write

movlw 0x45 ; E

call Data_Write

movlw 0x52 ;R

38

call Data_Write

movlw 0x45 ;E

call Data_Write

;third line

movlw 0X099; COMMAND TO MOVE TO THIRD LINE

call send_lcd

movlw 0X54 ; T

call Data_Write

movlw 0X45 ; E

call Data_Write

movlw 0X58 ; X

call Data_Write

movlw 0x54 ; T

call Data_Write

; forth line

movlw 0X0D7; lcd command to move to line4

call send_lcd

movlw 0X30 ; 0

call Data_Write ;

movlw 0X37 ;7

call Data_Write ;

movlw 0X31 ; 1

call Data_Write ;

movlw 0X39 ; 9

call Data_Write ;

movlw 0X33 ; 3

call Data_Write ;

movlw 0X39 ; 9

call Data_Write ;

movlw 0X33 ; 3

39

call Data_Write ;

movlw 0X32 ; 2

call Data_Write

movlw 0X31 ; 1

call Data_Write

movlw 0X32 ; 2

call Data_Write

movlw d'100';delay

call LOOPX

movlw d'100';wait

call LOOPX

movlw d'100'; wait

call LOOPX

movlw d'100'; wait

call LOOPX

LOOP:

call Rcv_RS232 ; function to receive from GSM

goto LOOP;recheck the above function

XMIT_RS232: ;transmitting

btfss PIR1, TXIF ;xmit buffer empty?

GOTO XMIT_RS232 ;no, wait

MOVWF TXREG ;now send

RETURN

Rcv_RS232:

BTFSS PIR1, RCIF ; check for received data

GOTO Rcv_RS232

40

MOVF RCREG, W; move received data to RCREG

CALL Data_Write

RETURN

END; end of entire program

41

B. PIC16f690 Internal Architecture

Appendix Figure 1. 1 Internal Architecture of PIC16F690 [3]

42

C. Circuit Diagram

43

D. Cost of Materials

Table 1 Cost of Materials

ITEM No PARTICULARS COST

(Ksh)

1 GSM MODEM(SIM 900GSM/GPRS) 3000

2 20x4 LCD Screen(LM044L) 1100

3 Breadboard 200

4 Potentiometer(100K) 20

5 Voltage Regulator(LM7805) 30

6 Connecting Wires(Assorted pack) 350

7 Transistor-(2N7000) 20

8 PIC16F690 IC 450

9 Resistors(2-10ohms0) 20

10 20 pin dip socket 30

11 PICKIT 3 (Microchip) 2500

12 Printed circuit board (15x14)cm 500

TOTAL 8220