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Microcontrollers –

Get to know about them and design

your own projects

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Table of Contents

Chapter 1: Microcontrollers Page No.

1.1 Introduction to Microcontrollers 9

1.2 Brief about microprocessors 10

1.3 Types of microprocessors 11

1.4 How are microcontrollers different from microprocessors 12

1.5 How are microcontrollers classified? 13

1.5.1 Classification according to number of bits

1.5.2 Classification according to memory devices

1.5.3 Classification according to instruction set

1.5.4 Classification according to memory architecture

1.6 Summary 16

Chapter 2: Microcontroller 8051

2.1 Introduction 17

2.1.1 History

2.2.2 Brief Idea

2.2 8051 Architecture 18

2.3 8051 Pin Description 21

2.4 8051 Application areas 23

2.5 Summary 24

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Chapter3- AVR Microcontrollers

3.1 Introduction 25

3.1.1 History

3.1.2 How are AVR microcontrollers different from 8051 microcontrollers?

3.1.3 How are AVR microcontrollers classified?

3.2 ATMega328 26

3.2.1 Key Features

3.2.2 Pin Description

3.3 ATMega32 28

3.3.1 Introduction

3.3.2 Key Features

3.3.3 Different sleep modes in ATMega32

3.3.4 Pin Description

3.3.5 Memory Structure

3.4 ATMega8 33

3.4.1 Introduction

3.4.2 ATMega8 architecture

3.4.3 ATMega8 pin description

3.4.4 ATMega8 sleep modes

3.5 Summary 39

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Chapter 4- PIC Microcontrollers

4.1 Introduction 40

4.1.1 Brief idea about PIC microcontrollers

4.1.2 Key features

4.2 Pin Description of PIC microcontroller 42

4.3 PIC microcontroller architecture 45

4.4 Summary 49

Chapter5- ARM microcontrollers

5.1 Introduction 50

5.1.1 History

5.1.2 ARM usage

5.1.3 ARM different versions and key features

5.2 ARM architecture 52

5.3 ARM7 54

5.4 Summary 55

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Chapter 6- Renesas microcontrollers

6.1 Introduction 56

6.2 Pin description 56

6.3 Architecture 57

6.4 Summary 59

Chapter 7- Microcontroller communication

7.1 Introduction 60

7.2 Inter system protocol 60

7.2.1 UART

7.2.2 USART

7.2.3 USB

7.2.4 Difference between inter system protocols

7.3 Intra system protocols 63

7.3.1 I2C protocol

7.3.2 SPI

7.3.3 CAN

7.4 Microcontroller communication with Computers 66

7.4.1 How is microcontrollers interfaced to computers/CPU?

7.4.2 RS232 Cable

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7.4.3 Max232

7.5 Summary 72

Chapter 8- Programming a microcontroller

8.1 Introduction to programming a microcontroller 73

8.2 Assembly level language programming 73

8.2.1 8051 RAM memory structure

8.2.2 Assembly level language coding

8.2.3 Steps in writing and executing a program

8.3 C Language program 76

8.3.1 Software used in microcontroller program

8.3.2 How to use Kiel software to write microcontroller program?

8.3.3 Steps in developing a microcontroller program

8.4 Summary 84

Chapter 9 – Microcontroller Interfacing

9.1 Microcontroller interfacing with matrix keypad 85

9.1.1 What is matrix keypad?

9.1.2 How is matrix keypad interfaced to 8051 microcontroller?

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9.2 Motor interfacing to microcontroller 86

9.2.1 Introduction to LM293D-Motor driver IC

9.2.2 How is motor interfaced to 8051 microcontroller?

9.3 Relay interfacing to 8051 microcontroller 88

9.3.1 Introduction to relay drivers

9.3.2 Interfacing relay with microcontroller using ULN2003

9.3.3 Interfacing relay with microcontroller using transistors

9.4 16 by 2 LCD display interfacing with microcontrollers 89

9.5 Summary 91

Chapter 10 – Designing your own microcontroller based projects

10.1 Step by step guide to build your own microcontroller projects 92

10.1.1 Introduction and theory about the project

10.1.2 Step1 - Circuit designing

10.1.3 Step 2- Microcontroller program coding

10.1.4 Step 3- Circuit drawing

10.1.5 Step 4 – Code dumping

10.1.6 Step 5- Simulating the circuit

10.2 Few microcontroller based projects 100

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10.2.1 Controlling loads using microcontroller

10.2.2 Motor speed control using microcontroller

10.2.3 GSM based monthly energy meter billing using microcontroller

10.2.4 Automatic dialing to any telephone on detecting burglary

10.3 Few microcontroller based circuits 105

10.3.1 Lamp switching using PIC microcontroller

10.3.2 Programmed message sending circuit

10.3.3 Intra system communication in automobiles

10.4 Summary 108

Ending Stuff 109

About the authors

Rights to readers

Legal Info

Ways to interact

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Chapter 1- Microcontrollers

1.1. Introduction to Microcontrollers

A microcontroller is a small, low-cost and self contained computer-on-a-chip that can be used as

an embedded system. It is a computer on‐a‐chip optimized to manage electric gadgets. It is

intended particularly for precise tasks like controlling a particular system. A micro-controller can

be abbreviated as µC, or MCU.

Also, a micro-controller is a fraction of a fixed in system, which is fundamentally a complete

circuit board. A fixed-in system is a computer system intended to carry out one or more

functions over and over again with real‐time work out limits. It is embedded as an element of a

full machine often counting hardware and motorized elements as well.

Examples of micro-controllers are the 8051, Intel’s 80196, Microchip’s PIC and Motorola’s

68HCxx series. Micro-controllers which are normally incorporated in toys, automobiles,

appliances and office machines are gears which amalgamate a number of constituents of a micro-

processor system on a solo microchip.

A few microcontrollers may utilize four-bit expressions and work at clock rate frequencies,

which usually include:

An 8 or 16 bit microprocessor.

A little measure of RAM.

Programmable ROM and flash memory.

Parallel and serial I/O.

Timers and signal generators.

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Analog to Digital and Digital to Analog conversion

1.2 Brief about microprocessors

A microprocessor is an electronic computer component crafted from miniature sized transistors

& some other circuitry elements on a solitary semi-conductor IC (integrated circuit) or micro

chip. The CPU (central processing unit) is the most renowned micro-processor, but numerous

other constituents in a computer contain them, like- the GPU (Graphics Processing Unit) on a

video card. In the race of personal computers, the names CPU & microprocessor are applied

inter-changeably. At the Center of all PCs and at maximum of the workstations a microprocessor

is incorporated. Microprocessors control the logic of approximately all digital machines, from

radios clock to fuel injection structures for automobile.

Figure 1.1 Microprocessor on board

There are mainly five types of microprocessors. These minute units provide computers with a

“brain”. Inside a usual silicon micro-processor, there will be a number of minute transistors and

tremendously tiny parts. All of these components are employed to assist a computer work as

planned.

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1.2.1 Types of Microprocessors

Complex Instruction Set Microprocessors:

This type of microprocessor is also known as CISM. CISM classify a micro-processor in which

each & every order can be executed together with several other low-level functions. These

functions are intended to carry out actions such as- uploading data into memory card, re-calling

or downloading data from memory card or a complex mathematics computation in a single

command.

Reduced Instruction Set Microprocessors:

Also known as RISC, this was intended to pace up computer microprocessors. These chips are

built up under the guideline that permits the microprocessor to do a smaller amount of things

within each command and this will permit it to complete more commands more rapidly.

Superscalar processors:

These types of processors resemble the hardware on the micro-processor so that it can perform

numerous instructions at the same time. These replica resources can be committed arithmetic

logic units or multipliers. Super scalars comprise of several operational units. Superscalar micro-

processors carry out more than one command throughout a single clock cycle by concurrently

transmitting numerous instructions to superfluous operational units in the processor.

The Application Specific Integrated Circuit:

Also known as ASIC microprocessor is intended for extremely precise purposes, which possibly

will comprise- automotive emissions control or Personal Digital Assistants computers. ASICs at

times is produced to specification, but can also be manufactured by making use of off-the-shelf

gears.

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Digital Signal Multiprocessors (DSPs):

DSPs are unique micro-processors employed to decode & encode video, or convert digital or

video to analog and vice-versa. These operations need a micro-processor particularly excellent at

carrying out mathematical calculations. DSP chips are generally employed in SONAR, mobile

telephones, RADAR, home theater audio gears and cable set-top boxes.

1.3 How are microcontrollers different from microprocessors?

The dissimilarity between the two is that a micro-controller integrates the features of a

microprocessor (ALU, CPU, Registers) together with the existence of extra characteristics such

as existence of ROM, RAM, counter, Input/ Output ports, etc. On the contrary, a micro-

controller controls the function of a device by employing fixed programs accumulated in ROM

that does no amend with duration.

From one more point of view, the major dissimilarity amid a usual micro-processor and a micro

controller parting there architectural terms is the area of their application. Usual microprocessors

such as the Pentium family or Intel Core family processors or alike processors are in computers

as a universally functioning programmable machine. In its life span it has to manage numerous

different assignments and programs specified to it. In contrast a micro-controller of PIC family

or 8051 family or any other have noticed their applications in tiny embedded systems such as-

control system of traffic signals or some sort of robotic system. Also these gadgets manage

similar task or similar program all through their entire life cycle.

Another difference is that the microcontroller generally has to handle instantaneous tasks

whereas on the contrary the micro-processors in a computer system perhaps will not handle an

instantaneous task at all times.

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1.4 How are microcontrollers classified?

The microcontrollers are characterized according to bus-width, instruction set, and memory

structure. For the same family, there may be different forms with different sources.

The types of microcontroller is shown in figure, they are characterized by their bits, memory

architecture, memory/devices and instruction set. Let’s discuss briefly about it.

1.4.1 Classification According to Number of Bits

The bits in microcontroller are 8-bits, 16-bits and 32-bits microcontroller.

8- Bit Microcontroller- In 8-bit microcontroller the internal bus is 8-bit. When in-house bus in

a MCU is 8-bit bus then the ALU carries out the logic & arithmetic operations on a byte at an

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order. The MCU is 8-bit micro-controller. The examples of 8-bit microcontrollers are Intel

8031/8051, PIC1x and Motorola MC68HC11 families.

16 bit Microcontroller- A 16 bit Microcontroller consists of a 16 bit bus and the ALU performs

arithmetic and logic operations on the 16 bit operand. It provides greater precision and

performance as compared to 8 bit MCU.

For example 8 bit microcontrollers can only use 8 bits, resulting in a final range of 0×00 – 0xFF

(0-255) for every cycle. In contrast, 16 bit microcontrollers with its 16 bit data width has a range

of 0×0000 – 0xFFFF (0-65535) for every cycle. A longer timer most extreme worth can likely

prove to be useful in certain applications and circuits. It can automatically operate on two 16 bit

numbers. Some examples of 16-bit microcontroller are 16-bit MCUs are extended 8051XA,

PIC2x, Intel 8096 and Motorola MC68HC12 families.

32 bit microcontroller- The 32-bit microcontroller uses the 32-bit instructions to perform the

arithmetic and logic operations. When in-house bus for the data transmitting function in an MCU

is 32-bit bus then the ALU carries out logic & arithmetic functions on operand words of 32 bits

at the orders. The MCU is 32-bit micro-controller. These supply better accuracy and

performance in comparison to the 16-bit MCUs.

These are used in automatically controlled devices including implantable medical devices,

engine control systems, office machines, appliances and other types of embedded systems. Some

examples are Intel/Atmel 251 family, PIC3x.

1.4.2 Classification According to Memory Devices

The memory devices are divided into two types, they are

Embedded memory microcontroller: When an embedded system has a microcontroller unit

that has all the functional blocks available on a chip is called an embedded microcontroller. It

has hardware and software embedded into a single unit. . Extremely few or no extra peripheral

unit or system exists for processing during the control or making use of the peripheral d For

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example, 8051 having program & data memory, I/O ports, serial communication, counters and

timers and interrupts on the chip is an embedded microcontroller.

External Memory Microcontroller: When an embedded system has a microcontroller unit that

has not all the functional blocks available on a chip, it is called an external memory

microcontroller. It has memory externally interfaced to the hardware. It is also known as

peripheral memory. For example, 8031 has no program memory on the chip is an external

memory microcontroller. An 8031 microcontroller comprises of a program memory which is

interfaced outwardly to it.

1.4.3 Classification According to Instruction Set

CISC: CISC is a Complex Instruction Set Computer. It allows the programmer to use one

instruction in place of many simpler instructions.

RISC: The RISC is stands for Reduced Instruction set Computer; this type of instruction sets

reduces the design of microprocessor for industry standards. It allows each instruction to operate

on any register or use any addressing mode and simultaneous access of program and data.

Example for CISC and RISC:

CISC: Mov AX, 4 RISC:

Mov AX, 0

Mov BX, 2

Mov BX, 4

ADD BX, AX

Mov CX, 2

Begin ADD AX, BX

Loop Begin

From above example, RISC systems shorten execution time by reducing the clock cycles per

instruction and CISC systems shorten execution time by reducing the number of instructions per

program. The RISC gives a better execution than the CISC.

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1.4.4 Classification According to Memory Architecture

Memory architecture of microcontroller are two types, they are namely:

Harvard Memory Architecture Microcontroller: In this type of architecture, the

microcontroller has different memory for program instructions and data. It consists of two

separate buses for instructions and data.

Von Neumann Memory Architecture Microcontroller: In this type of architecture, the

microcontroller has same memory for program instructions and data. It consist of only one bus to

carry both instructions and data.

1.5 Summary

Microcontrollers are digital integrated chips which contain the processor as well as the memory

embedded on the same chip. They are mostly used in embedded systems. Microcontrollers differ

from microprocessors in their architecture as well as their functioning. Different microcontrollers

can be classified based on the number of instruction bits, memory architecture, and instruction

set architecture and memory devices.

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Chapter2 - 8051 Microcontrollers

2.1 Introduction

2.1.1 History

The 8051 Microcontroller was designed in 1980’s by Intel. Its foundation was based on Harvard

Architecture and was developed principally for bringing into play in Embedded Systems. At first

it was created by means of NMOS technology but as NMOS technology needs more power to

function therefore Intel re-intended Microcontroller 8051 employing CMOS technology and a

new edition came into existence with a letter ‘C’ in the title name, for illustration: 80C51. These

most modern Microcontrollers need fewer amount of power to function in comparison to their

forerunners.

Microcontroller 8051

2.1.2 Brief Idea

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There are two buses in 8051 Microcontroller -one for program and other for data. As a result, it

has two storage rooms for both program and data of 64K by 8 sizes. The microcontroller

comprises of 8 bit accumulator & 8 bit processing unit. It also consists of 8 bit B register as

majorly functioning blocks. It also has a number of other 8 bit and 16 bit registers.

For internal functioning & processing, microcontroller 8051 comes with integrated built-in

RAM. This is prime memory and is employed for storing temporary data. It is unpredictable

memory i.e. its data can get be lost when the power supply to the microcontroller is switched

OFF.

2.2 8051 Architecture

Microcontroller 8051 block diagram is shown below. Let’s have a closer look at each & every

fraction or block of this design:

8051 architecture

CPU (Central Processor Unit)

Central Processor Unit or CPU is the ‘brain’ of any processing machine. It scrutinizes and

manages all processes that are carried out in the Microcontroller. User has no power over the

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functioning of CPU. It interprets all program instructions stored in storage space (ROM) and

carries out all of them and does the projected duty.

Interrupts

Interrupt is a sub-routine call that reads the Microcontroller’s key function or job and helps it to

perform some other program which is extra important at that point of time. The characteristic of

Interrupt is extremely constructive as it aids in emergency cases. Interrupts provides us a method

to postpone or delay the current process, carry out a sub-routine task and then all over again

restart standard program implementation.

The Micro-controller 8051 can be assembled in such a manner that it momentarily stops or break

the core program at the happening of interrupt. When sub-routine task is finished then the

implementation of core program initiates automatically as usual. There are 5 interrupt supplies in

8051 Microcontroller, two out of five are peripheral interrupts, two are timer interrupts and one

is serial port interrupt.

Memory

Micro-controller needs a program which is a set of commands. This program enlightens

Microcontroller to perform precise tasks. These programs need a storage space on which they

can be accumulated and implemented by microcontroller to act upon any specific process. The

memory which is brought into play to accumulate the program of Microcontroller is recognized

as Program memory or code memory. In common language it’s also known as Read Only

Memory or ROM.

Micro-controller also needs a memory to amass data or operands for the short term. The storage

space which is employed for momentarily data storage is known as Data Memory and we

employ Random Access Memory or RAM for this principle reason. Microcontroller 8051

contains code memory or program memory 4K so that is has 4KB Rom and it also comprise of

data memory (RAM) of 128 bytes.

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Bus

Fundamentally, Bus is a group of wires which functions as a communication canal or mean for

the transfer Data. These buses comprise of 8, 16 or more cables. As a result, a bus can bear 8

bits, 16 bits all together. There are two types of buses:

1. Address Bus:

Microcontroller 8051 consists of 16 bit address bus. It is brought into play to address memory

positions. It is also utilized to transmit the address from Central Processing Unit to Memory.

2. Data Bus:

Microcontroller 8051 comprise of 8 bits data bus. It is employed to cart data.

Oscillator

As we all make out that Microcontroller is a digital circuit piece of equipment, thus it needs

timer for its function. For this function, Microcontroller 8051 consists of an on-chip oscillator

which toils as a time source for CPU (Central Processing Unit). As the productivity thumps of

oscillator are steady as a result, it facilitates harmonized employment of all pieces of 8051

Microcontroller.

Input/output Port

A microcontroller is employed in embedded systems to manage the functions of devices. Thus to

gather it to other machinery, gadgets or peripherals we need I/O (input/output) interfacing ports

in Micro-controller. For this function Micro-controller 8051 consists of 4 input/output ports to

unite it to other peripherals.

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Timers/Counters

Micro-controller 8051 is incorporated with two 16 bit counters & timers. The counters are

separated into 8 bit registers. The timers are utilized for measuring the intervals, to find out pulse

width etc.

2.3 8051 Pin descriptions

For explaining the pin diagram and pin configuration of microcontroller 8051, we are taking into

deliberation a 40 pin Dual inline package (DIP). Now let’s study through pin configuration in

brief:-

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8051 pin diagram

Pins 1 – 8:- These pins form Port 1. Different from other ports, this port doesn’t provide any

other purpose. Port 1 is a domestically pulled up, quasi bi directional Input/output port.

Pin 9:- As made clear previously RESET pin is utilized to set the micro-controller 8051 to its

primary values, whereas the micro-controller is functioning or at the early beginning of

application. The RESET pin has to be set elevated for two machine rotations.

Pins 10 – 17:- recognized as Port 3. This port also supplies a number of other functions such as

timer input, interrupts, serial communication indicators TxD & RxD, control indicators for

outside memory interfacing WR & RD, etc. This is a domestic pull up port with quasi bi

directional port within.

Pins 18 and 19:- These are employed for interfacing an outer crystal to give system clock.

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Pin 20:- Titled as Vss – it symbolizes ground (0 V) association.

Pins- 21-28:- recognized as Port 2 (P 2.0 – P 2.7) – other than serving as Input/output port,

senior order address bus indicators are multiplexed with this quasi bi directional port.

Pin- 29:- Program Store Enable or PSEN is employed to interpret sign from outer program

memory.

Pin-30:- External Access or EA input is employed to permit or prohibit outer memory

interfacing. If there is no outer memory need, this pin is dragged high by linking it to Vcc.

Pin-31:- Aka Address Latch Enable or ALE is brought into play to de-multiplex the address data

indication of port 0 (for outer memory interfacing). Two ALE throbs are obtainable for every

machine rotation.

Pins 32-39: These pins are recognized as Port 0 (P0.0 to P0.7) pins – other than serving as

Input/output port, low order data & address bus signals are multiplexed with this port (to provide

the use of outer memory interfacing).

This pin is a bi directional Input/output port (the single one in microcontroller 8051) and outer

pull up resistors are necessary to utilize this port as Input/output.

Pin-40: termed as Vcc is the chief power supply. By and large it is +5V DC.

2.4 8051 application areas

The microcontroller 8051 has been in application in a large amount of machines, principally

because it is simple to incorporate in a project or to assemble a machine around it. The following

are the key spots of spotlight:

Energy Management

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Competent measuring device systems aid in calculating energy consumption in domestic and

industrialized applications. These meter systems are prepared competent by integrating

microcontrollers.

Touch screens

A high degree of microcontroller suppliers integrate touch sensing abilities in their designs.

Transportable devices such as media players, gaming devices & cell phones are some

illustrations of micro-controller integrated with touch sensing screens.

Automobiles

The microcontroller 8051 discovers broad recognition in supplying automobile solutions. They

are extensively utilized in hybrid motor vehicles to control engine variations. In addition,

works such as cruise power and anti-brake mechanism has created it more capable with the

amalgamation of micro-controllers.

Medical Devices

Handy medicinal gadgets such as glucose & blood pressure monitors bring into play micro-

controllers, to put on view the measurements, as a result, offering higher dependability in

giving correct medical results.

2.5 Summary

8051 Microcontroller is a 40 pin, 8 bit microcontroller based on Harvard architecture wherein the

program memory and data memory are different. The 8051 microcontroller consists of four Input

/ Output ports out of which one port pins can also be used as interrupt pins. The microcontroller

works with an oscillator frequency of 11MHz.

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Chapter 3- AVR Microcontrollers

3.1 Introduction

3.1.1 History

AVR microcontroller was developed by Alf-Egil Bogen and Vegard Wollan from Atmel

Corporation. The AVR microcontrollers are based on modified Harvard RISC architecture with

separate memories for data and program and speed of AVR are high when compared to 8051 and

PIC. The AVR is stands for Alf-Egil Bogen and Vegard Wollan’s RISC processor.

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3.1.2 How are AVR microcontrollers different from 8051 microcontrollers?

8051s are 8-bit controllers based on CISC architecture, AVRs are 8-bit controllers based on

RISC architecture

8051 consumes more power than AVR microcontroller

In 8051, we can program easily than the AVR microcontroller

The speed of AVR is more than the 8051 microcontroller

3.1.3 How are AVR microcontrollers classified?

AVR Microcontrollers are classified into three types:

Tiny AVR – Less memory, small size, suitable only for simpler applications

Mega AVR – These are the most popular ones having good amount of memory (up to 256

KB), higher number of inbuilt peripherals and suitable for moderate to complex applications

Xmega AVR – Used commercially for complex applications, which require large program

memory and high speed

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3.2 ATMega328

3.2.1 Key Features

28-pin AVR microcontroller

Flash program memory of 32kbytes

EEPROM data memory of 1kbytes

SRAM data memory of 2kbytes

I/O pins are 23

Two 8-bit timers

A/D converter

Six channel PWM

In built USART

External Oscillator: up to 20MHz

3.2.2 Pin Description

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ATMega328 pin diagram

Vcc: Digital supply voltage.

GND: Ground.

Port B: Port B is an 8-bit bi-directional I/O port. The Port B pins are tri-stated when a reset

condition becomes active or one, even if the clock is not running.

Port C: Port C is a 7-bit bi-directional I/O port with internal pull-up resistors.

PC6/RESET

Port D: It is an 8-bit bi-directional I/O port with internal pull-up resistors. The output buffers of

the Port D consist of symmetrical drive characteristics.

AVcc: AVcc is the supply voltage pin for the ADC.

AREF: AREF is the analog reference pin for the ADC.

3.3 ATMega32

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3.3.1 Introduction

These AVR microcontrollers are based on the advanced RISC architecture. ATmega32 is a low

power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. AVR can

execute 1 million instructions per second if cycle frequency is 1MHz.

ATMega32

3.3.2 Key Features

32 x 8 general working purpose registers.

32K bytes of in system self programmable flash program memory

2K bytes of internal SRAM

1024 bytes EEPROM

Available in 40 pin DIP, 44 lead QTFP, 44-pad QFN/MLF

32 programmable I/O lines

8 Channel, 10 bit ADC

Two 8-bit timers/counters with separate prescalers and compare modes

One 16-bit timer/counter with separate prescaler, compare mode and capture mode.

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4 PWM channels

In system programming by on-chip boot program

Programmable watch dog timer with separate on-chip oscillator.

Programmable serial USART

Master/slave SPI serial interface

Six sleep modes: Idle, ADC noise reduction, power-save, power-down, standby and extended

standby.

Internal calibrated RC oscillator

External and internal interrupt sources

Power on reset and programmable brown-out detection.

3.3.3 Different sleep modes in ATMega32

Power down mode- The power-down saves the register contents but freezes the oscillator. All

other chip functions will be disabled until the next external interrupt arises. Asynchronous timer

allows the user to maintain a timer based in power-save mode while the rest of the device is

sleeping.

AC Noise reduction mode- ADC noise reduction mode stops the CPU and all I/O modules

except ADC and asynchronous timer.

Standby mode- In standby mode, except crystal oscillator the rest of the device is sleeping. Both

the main oscillator and asynchronous timer continue to run in extended standby mode.

3.3.4 Pin Description of ATMega32

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ATMega32 Pin Diagram

Pin Descriptions:

VCC: Digital voltage supply

GND: Ground

Port A (PA7-PA0): This port serves as analog inputs to the A/D converter. It also serves as an

8-bit bidirectional I/O port if the A/D converter is not used.

Port B (PB7-PB0) & Port D (PD7-PD0): It is an 8-bit bidirectional I/O port. Its output buffers

have symmetrical drive characteristics with both high sink and source capability. As inputs, these

are extremely pulled low if the pull-up resistors are activated. It also serves various special

function features of the ATmega32.

Port C (PC7-PC0): It is an 8-bit bidirectional I/O port. If the JTAG interface is enabled, the

pull-up resistors on pins PC5 (TDI), PC3 (TMS), and PC2 (TCK) will be activated.

Reset: It is an input.

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XTAL1: It is an input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

XTAL2: It is an output from the inverting oscillator amplifier.

AVCC: It is the supply voltage pin for Port A and A/D converter. It should be connected to

VCC.

AREF: AREF is the analog reference pin for the A/D converter.

3.3.5 ATMega32 memory structure

In System Programmable Flash Program Memory:

ATmega32 contains 32Kbytes on-chip in system reprogrammable flash memory for program

storage. Flash is organized as 16k X 16 and its memory is divided into two sections Boot

program section and application program section.

ISP Programmer circuit

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ATMega32 Architecture

SRAM Data Memory

The Register file, I/O memory, and the internal data SRAM are addressed by the lower 2144 data

memory locations. The first 96 locations address the Register file and I/O memory, and the

internal data SRAM is addressed by the next 2048 locations. Direct, indirect with displacement,

indirect, indirect with pre-decrement, and in-direct with post decrement are the 5 different

addressing modes for the data memory covering. The 32 general purpose registers, 64 I/O

registers, and 2048 bytes of internal data SRAM are accessible by using these addressing modes.

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EEPROM Data Memory

It contains 1024 bytes of data EEPROM memory. It can be accessed as a separate data space in

which single bytes can be read and written.

I/O Memory:

All I/Os and peripherals are placed in the I/O space. The I/O locations are accessed by the IN and

OUT instructions, transferring the data between the 32 general purpose registers and the I/O

space. I/O registers with in the address 00-1F are directly bit accessible using the SBI and CBI

instructions.

3.4 ATMega8

3.4.1 Introduction

It is an 8 bit CMOS built microcontroller from the AVR family (developed by Atmel

Corporation in 1996) and is built on the RSIC (Reduced Instruction Set Computer) architecture.

Its basic advantage is it doesn’t contain any accumulator and the result of any operation can be

stored in any register, defined by the instruction.

ATMega8 Microcontroller

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3.4.2 ATMega8 architecture

ATMega8 architecture

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Memory

It consists of 8KB of flash memory, 1KB of SRAM and 512 Bytes of EEPROM. The 8K flash is

divided into 2 parts- lower part used as boot flash section, and upper part used as application

flash section. The SRAM contains 1K bytes along with 1120 bytes of general purpose registers

and I/O registers. The lower 32 address locations are used for 32 general purpose 8 bit registers.

The next 64 address are used for I/O registers. All the registers are connected directly to the

ALU. The EEPROM is used to store user defined data.

Input/output ports

It consists of 23 I/O lines with 3 I/O ports, named B, C and D. Port B consists of 8 I/O lines, Port

C consists of 7 I/O lines and Port D consists of 8 I/O lines.

Registers corresponding to any port X (B,C or D) are:

DDRX: Port X data direction register

PORTX: Port X data register

PINX: Port X input register

Timers and Counters

It consists of 3 timers with comparable modes. Two of them are 8 bit whereas the third one is 16

bit.

Oscillators

It incorporates internal reset and oscillator which makes it possible to eliminate the need for any

external input. The internal RC oscillator is capable of generating internal clock which can run at

any frequency of 1MHz, 2MHz, 4MHz or 8MHz as programmed. It also supports external

oscillator with maximum frequency of 16MHz.

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Communication

It provides both synchronous and asynchronous data transfer schemes through USART

(Universal Synchronous and Asynchronous Receiver Transmitter), i.e. communication with

modems and other serial devices. It also supports SPI(Serial Peripheral Interface) used for

communication between devices based on the master-slave method. Another type of

communication supported is the TWI(Two wire Interface).

It allows commutation between any two devices by using 2 wires along with a common ground

connection.

It also has a comparator module integrated in the chip to provide comparison between two

voltages connected to the two inputs of the Analog comparator through the external chips.

It also contains a 6 channel ADC out of which 4 have 10 bit accuracy and 2 have 8 bit accuracy.

Status Register: It contains information about the currently executed arithmetic instruction set.

3.4.3 ATMega8 Pin diagram

ATMega8 Pin Diagram

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Pins 23,24,25,26,27,28 and 1 are used for port C, whereas pins 9,10,14,15,16,17,18,19 are

used for port B and pins 2,3,4,5,6,11,12 are used for port D.

Pin 1 is also the Reset pin and applying low level signal for a time longer than the minimum

pulse length will generate a reset.

Pins 2 and 3 are also used for serial communication for USART.

Pins 4 and 5 are used as external interrupts. One of them will trigger when interrupt flag bit of

status register is set and the other will trigger as long as the interrupt condition prevails.

Pins 9 and 10 are used as external oscillator as well as timer counters oscillators where the

crystal is connected directly between the pins. Pin 10 is used for crystal oscillator or low

frequency crystal oscillator. If the internal calibrated RC oscillator is used as the clock source

and the asynchronous timer is enabled, these pins can be used as a timer oscillator pins.

Pin 19 is used as Master Clock output, slave clock input for SPI channel.

Pin 18 is used as Master clock input, slave clock output.

Pin 17 is used as Master data output, slave data input for SPI channel. It is used as a input

when enabled by a slave and is bidirectional when enabled by the master. This pin can also be

used as a output compare match output, which serves as an external output for the

timer/counter compare match.

Pin16 is used as a slave select input. It can also be used as a timer/counter1 compare match by

configuring the PB2 pin as an output.

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Pin15 can be used as an external output for the timer/counter compare match A.

Pins 23 to 28 are used for ADC channels. Pin 27 can also be used as Serial interface clock and

pin 28 can be used as serial interface data

Pins 13 and 12 are used as Analog Comparator inputs.

Pins 11 and 6 are used as timer/counter sources.

3.4.4 ATMega8 sleep modes

The Microcontroller operates in 6 sleep modes.

Idle Mode: It stops the functioning of the CPU, but allows operation of SPI, USART, ADC,

TWI, Timer/Counter, and Watchdog and interrupts system. It is achieved by setting SM0 to

SM2 bits of MCU register flag to zero.

ADC Noise Reduction Mode: It stops the CPU but allows functioning of ADC, external

interrupts, timer/counter2 and watchdog.

Power down Mode: It enables external interrupts, the 2-wire serial interface, watchdog while

disabling the external oscillator. It stops all generated clocks.

Power save Mode: It is used when Timer/Counter is clocked asynchronously. It halts all

clocks except clkASY.

Stand By mode: In this mode, the oscillator is allowed to operate, halting all other

operations.

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3.5 Summary

AVR microcontrollers are RISC based controllers, manufactured by Atmel group. They consist

of built is features like timers, analog to digital converters etc. Different AVR microcontrollers

are ATMega8, ATMega32, and ATMega328 etc. ATMega8 is a 28 pin microcontroller with

8KB of program memory and 1536 bytes of data memory. ATMega32 is a 40 pin

microcontroller with 32 programmable input/output lines. ATMega328 is a 28 pin

microcontroller with program memory of 32KB and data memory of 3KB.

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Chapter 4- PIC Microcontrollers

4.1 Introduction

4.1.1 Brief idea about PIC microcontrollers

PIC is a peripheral interface controller, developed by general instrument’s microelectronics, in

the year of 1993. It is controlled by the software. They could be programmed to complete many

task and control a generation line and many more. PIC microcontrollers are finding their way

into new applications like smart phones, audio accessories, video gaming peripherals and

advanced medical devices.

PIC microcontroller

There are many PICs, started with PIC16F84 and PIC16C84. But these were the only affordable

flash PICs. Microchip has recently introduced flash chips with types that are much more

attractive, such as 16F628, 16F877 and 18F452. The 16F877 is around twice the price of the old

16F84, but has eight times the code size, much more RAM, much more I/O pins, a UART, A/D

converter and a lot more.

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4.1.2 Key Features about PIC microcontrollers

Core Features:

High-performance RISC CPU

Up to 8K x 14 words of FLASH program memory

35 Instructions (fixed length encoding-14-bit)

368×8 static RAM based data memory

Up to 256 x 8 bytes of EEPROM data memory

Interrupt capability (up to 14 sources)

Three addressing modes (direct, indirect, relative)

Power-on reset (POR)

Harvard architecture memory

Power saving SLEEP mode

Wide operating voltage range: 2.0V to 5.5V

High sink / source current: 25mA

Accumulator based machine

Peripheral Features

3 Timer/counters (programmable pre-scalars): Timer0, Timer2 are 8-bit timer/counter with 8-

bit pre-scalar. Timer1 is 16-bit, can be incremented during sleep via external crystal/clock

Two capture, compare, PWM modules: Input capture function records the Timer1 count on a

pin transition. A PWM function output is a square wave with a programmable period and duty

cycle.

10-bit 8 channel analog-to-digital converter

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USART with 9-bit address detection

Synchronous serial port with master mode and I2C Master/Slave

8-bit parallel slave port

Analog Features:

10-bit, up to 8-channel Analog-to-Digital Converter (A/D)

Brown-out Reset (BOR)

Analog Comparator module (Programmable input multiplexing from device inputs and

comparator outputs are externally accessible).

4.2 Pin description

PIC pin diagram

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45

46

4.3 PIC Microcontroller architecture

The PIC microcontroller is based on RISC architecture. Its memory architecture follows the

Harvard pattern of separate memories for program and data, with separate buses.

PIC architecture

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1. Memory Structure

The PIC architecture consists of two memories- Program memory and the data memory

Program Memory: - It is a 4K*14 memory space. It is used to store the 13 bit instructions or the

program code. The program memory data is accessed by the program counter register which

holds the address of the program memory. The address 0000H is used as reset memory space and

0004H is used as interrupt memory space.

Data Memory: - The data memory consists of the 368 bytes of RAM and 256 bytes of

EEPROM

The 368 bytes of RAM consists of multiple banks. Each bank consists of general purpose

registers and special function registers.

The special function registers consists of control registers to control different operations of chip

resources like Timers, Analog to Digital Converters, Serial ports, I/O ports etc. For example, the

TRISA register whose bits can be changed to alter the input/output operation of port A.

The general purpose registers consists of registers used to store temporary data and the

processing results of the data. These general purpose registers are each 8 bit registers.

b. Working Register- It consists of memory space which stores the operands for each

instruction. It also stores the results of each execution.

c. Status Register- The bits of the status register denote the status of the ALU(arithmetic logic

unit) after every execution of the instruction. It is also used to select any one of the 4 banks

of RAM.

d. File Selection Register- It acts as a pointer to any other general purpose register. It consists

of the register file address and it is used in indirect addressing.

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Another general purpose register is the Program Counter register which is a 13 bit register. The 5

upper bits are used as PCLATH (Program Counter Latch) to independently function as any other

register and the lower 8 bits are used as the program counter bits. The program counter acts as a

pointer to the instructions stored in the program memory.

EEPROM- It consists of 256 bytes of memory space. It is a permanent memory like ROM but its

contents can be erased and changed during the operation of the microcontroller. The contents

into EEPROM can be read from or written to, using special function registers like EECON1,

EECON2, EEDATA etc.

2. I/O Ports- PIC16 series consists of 5 ports- Port A, Port B, Port C, Port D and Port E.

Port A – It is a 16 bit port, which can be used as input/output port based on the status of the

TRISA register.

Port B- It is an 8 bit port which can be used as both input and output. 4 of its bits when used as

input can be changed upon interrupt signals.

Port C- It is an 8 bit port whose operation (input or output) is determined by the status of the

TRISC register.

Port D- It is an 8 bit port which apart from being a I/O port acts as a slave port for connection to

microprocessor bus.

Port E- It is a 3 bit port which serves the additional function of control signals to the A/D

converter.

3. Timers

PIC microcontroller consists of 3 timers out of which Timer 0 and Timer 2 are 8 bit timers and

Time 1 is a 16 bit timer which can also be used as a counter.

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4. A/D Converter

The PIC Microcontroller consists of 8 channels, 10 bit Analog to Digital Converter. The

operation of A/D converter is controlled by the special function registers- ADCON0 and

ADCON1. The lower bits of the converter are stored in ADRESL (8 bits) and upper bits are

stored in ADRESH register. It requires an analog reference voltage of 5V for its operation.

5. Oscillators

Oscillators are used for timing generation. PIC microcontroller consists of external oscillators

like crystals or RC oscillators. In case of crystal oscillators, the crystal is connected between two

oscillator pins and the value of capacitor connected to each pin determines the mode of operation

of the oscillator. The different modes are low power mode, crystal mode and the high speed

mode. In case of RC oscillators, value of Resistor and Capacitor determine the clock frequency.

The clock frequency ranges from 30 KHz to 4 MHz

6. CCP module- A CCP module works in three modes-

Capture Mode- Captures the time of arrival of a signal or in other words captures the value of

Timer1 when CCP pin goes high.

Compare Mode- It acts as an analog comparator which generates an output when timer1 value

reaches a certain reference value.

PWM Mode: - It provides pulse width modulated output with 10 bit resolution and

programmable duty cycle.

7. Other special peripherals are like- Watchdog timer which resets the microcontroller incase of

any software malfunction, Brown out reset, which resets the microcontroller incase of any

power fluctuation and many more.

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4.4 Summary

PIC or peripheral inter phase microcontrollers are Harvard architecture based microcontrollers

and consist of RISC based processor. A PIC microcontroller consists of additional peripherals

like analog to digital converter, PWM module, timers etc. A PIC microcontroller has a fixed

instruction set of 35 instructions.

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Chapter 5-ARM Microcontrollers

5.1 Introduction

5.1.1 History

ARM stands for Advanced RISC (reduced instruction set computer) machine. ARM started as

part of Acorn makers of the BCC computer, and now designs chip for apple iPad. The first ARM

was established in Cambridge University in 1978. The Acorn group computers have developed

the first ARM commercial RISC processor in 1985. ARM was founded and became very popular

in 1990.

5.1.2 ARM usage

The ARM using more than 98% of the mobile phones in 2007 and 10 billion processors are

shipped in 2008. ARM is the latest technology which replaced by microcontroller and

microprocessors. Basically ARM is a 16 bit/ 32 bit Processors or Controllers. ARM is heart of

the advanced digital products like mobile phones automotive systems digital cameras and home

networking and wireless technologies.

5.1.3 ARM different versions and key features

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Version 1:

Software interrupts

26-bit address bus

Data processing is slow

It support byte, word and multiword load operations

Version 2:

26-Bit address bus

Automatic instructions for thread synchronization

Co-processor support

Version 3:

32-Bit addressing

Multiple data support (like 32 bit=32*32=64).

Faster than ARM version1 and version2

Version 4:

32-bit address space

Its support T variant:16 bit THUMB instruction set

It support M variant: long multiply means give a 64 bit result

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Version 5:

Improved ARM THUMB interworking

Its supports CCL instructions

It support E variant : Enhanced DSP Instruction set

It support S variant : Acceleration of Java byte code execution

Version 6:

Improved memory system

Its supports a single instruction multiple data

5.2 ARM architecture

ARM is based on reducing instruction set computer architecture; it means the core cannot

directly operate with the memory. All data operations must be done by registers with the

information which is located in the memory. Performing the operation of data and storing the

value back to the memory. ARM consists of 37 register sets, 31 general purpose registers and 6

are status registers. The ARM uses seven processing modes that are used to run the user task.

USER mode

FIQ mode

IRQ mode

SVC mode

UNDEFINED mode

ABORT mode

THUMB mode

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The user mode is a normal mode; which has least number of registers. It doesn’t have SPSR and

limited access to the CPSR.

The FIQ and IRQ are the two interrupt caused modes of the CPU. The FIQ is processing past

interrupt and IRQ is slandered interrupt. The FIQ mode has additional five banked registers to

provide more flexibility and high performance when critical interrupts are handling.

The Supervisor mode is the software interrupt mode of the processor to start up or reset.

The Undefined mode traps illegal instructions is executed. The ARM core consist 32-bit data bus

and faster data flow.

In THUMB mode the 32-bit of data divided into 16-bits and increases the processing speed.

Some of the registers are reserved in each mode for specific use by the core. The reserved

registers are

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SP (stack pointer).

LR (link register).

PC (program counter).

CPSR (current program status register).

SPSR (saved program status register).

The reserved registers are used for specific functions. The SPSR and CPSR contain the status

control bits specific properties. These properties are defining operating mode, ALU status flag,

Interrupt enable or disable flags. The ARM core is operated in two states - 32-bit state or

THUMBS state.

5.3 ARM 7

ARM 7 internal architecture

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The ARM7 is a 16/31 – Bit bus

The static Ram is 40 kb

On-chip flash programmable memory is 512kb

It is a high speed controller 60 MHz operation

Two 10 bit ADC converters provide a total of 14 analog inputs

One 10- bit D/A converter

Two 32 bit timers/counters

4- CCM (Capture Compare Modulation), 6-PWM, Watchdog timer

One RTC, 9 interrupts

One I2C protocol, SPI protocols, SSP protocol

Two UART serial communication protocols

5.4 Summary

ARM microcontrollers are based on advance RISC based processors. They are 32 bit

microcontrollers. They can be operated in two modes-thumb mode and normal mode. ARM

microcontroller families are ARM7, ARM9 and Cortex.

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Chapter 6- Renesas Microcontrollers

6.1 Introduction to Renesas Microcontrollers

Renesas is the latest automotive microcontroller family that offers high performance feature with

exceptionally low power consumption over a wide and versatile extension of items. This

microcontroller offers rich functional security and embedded safety characteristics required for

new and advanced automotive applications. The core structure of microcontroller CPU supports

high reliability and high performance requirements.

The RX Family of 32-bit microcontrollers is a feature rich, general purpose MCU covering a

wide range of embedded control applications with high speed connectivity, digital signal

processing and inverter control.

6.2 Pin Description of Renesas Microcontrollers

Renesas microcontroller pin description

It is a 20 pin microcontroller. The pin 9 is Vss, ground pin and Vdd, power supply pin. It has

three different kinds of interrupt, which are normal interrupt, fast interrupt, high speed interrupt.

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Normal interrupts store the significant registers on stack by using push and pop instructions. The

fast interrupts are automatically store program counter and processor status word in special

backup registers, so response time is faster. And high speed interrupts allocate up to four of the

general registers for dedicated use by the interrupt to expand speed even further. The internal bus

structure gives 5 internal busses to ensure data handling is not slowed down. Instruction fetches

occur via a wide 64-bit bus, so that due to the variable length instructions used in CISC

architectures.

6.3 Renesas Architecture

The RX microcontroller family uses a 32-bit enhanced Harvard CISC architecture to achieve

very high performance.

Renesas microcontroller architectural overview

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CPU- The main processor of the microcontroller is a 32 bit processor with maximum operating

frequency of 100MHz. It consists of 16 general purpose registers –R0 to R15, where R0 is also

the stack pointer register and the remaining registers are used as data or address registers. It also

consists of control registers like Interrupt stack pointer register, Program Counter, Processor

status word etc.

Memory- Memory module of the renesas microcontroller consists of 512KB ROM with two on-

chip programmable modules and off chip programmable modules, 96 KB of RAM and 32KB of

Flash memory.

Clock Generation Circuits- The renesas architecture consists of the main clock oscillator and

the sub clock oscillator. The CPU and other bus masters require a system clock frequency of 8 to

100MHz whereas the peripheral devices require a system clock frequency of 8 to 50MHz.

Additional Peripherals

Voltage Detection Circuit- This unit generates an interrupt signal to reset the microcontroller in

case the supply voltage falls below a fixed level.

A/D Converter- The microcontroller supports two in built analog to digital converter, one of 10

bit resolution and another with 12 bit resolution.

D/A Converter- The microcontroller consists of an inbuilt digital to analog converter with 2

channels and 10 bit resolution.

Timers- The microcontroller supports 7 timers- multifunction timer pulse unit ( 2 units with each

16 bit channel), Port output enable (controls the high impedance state of output pins),

Programmable pulse generator, 8 bit timers (produces pulses with variable duty cycle), compare

match timer and watchdog timer (1 channel of 14 bits).

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Communication devices- The microcontroller provides several peripherals for communication

like Ethernet Controller ( 10 to 100Mbps data rate), USB 2.0 host (12Mbps data rate), Serial

communication units like smart card interface, CAN(control area network) unit , serial peripheral

interface units.

6.4 Summary

Renesas microcontrollers are 32 bit microcontrollers based on Harvard architecture, with

variable instruction set. They consist of additional features like analog to digital converter,

digital to analog converter, watch dog timers etc. It consists of 512KB of flash Ethernet.

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Chapter 7- Microcontroller Communication

7.1 Introduction

By microcontroller communication, we refer to communication between two microcontrollers or

communication between a microcontroller and other devices. There a set of rules known as

protocols to govern this communication. The communication between a microcontroller and

devices on same chip/circuit is the intra system communication whereas the communication

between a microcontroller and devices on other chips/circuits is inters system communication.

7.2 Inter System Protocol

Inter System Protocol: The inter system protocol using to communicate the two different

devices. Like communication between computer to microcontroller kit. The communication is

done through a inter bus system.

Inter system protocol block diagram

Different categories of Inter system protocol:

UART Protocol

USART Protocol

USB Protocol

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7.2.1 UART Protocol

UART stands for universal asynchronous transmitter and receiver .UART Protocol is a serial

communication two wired protocol. The data cable signal lines are labeled as Rx and Tx. Serial

communication is commonly used for transmitting and receiving the signal. It transmits and

receives the data serially bit by bit without class pulses. The UART take bytes of data and sends

the individual bits in sequential manner. UART is a half duplex protocol. Half duplex means

transmitting and receiving the data but not at a same time. Most of the controllers have hardware

UART on board. It uses a single data line for transmitting and receiving the data. It has one start

bit, 8-bit data and one stop bit.

UART Protocol Structure

7.2.2 USART Protocol

USART stands for universal synchronous and asynchronous transmitter and receiver. It is a serial

communication two wire protocol. The data cable signal lines are labeled as Rx and TX. This

protocol is used to transmitting and receiving the data byte by byte along with the clock pulses. It

is a full-duplex protocol means transmitting and receiving data is simultaneously to different

board rates. Different devices communicate with microcontroller using this protocol. Ex:-

Telecommunications.

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USART protocol structure

7.2.3 USB Protocol

USB stands for universal serial bus. Again it is a serial communication two wire protocol. The

data cable signal lines are labeled D+ and D-. This protocol is used to communicate with the

system peripherals. USB protocol is used to send (receive) serial data to (from) the host and

peripheral devices. USB communication requires driver software which is based on the

functionality of the system. USB device can transfer data on the bus without any request to the

host computer.

Uses of USB protocol

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Now a day’s most of the devices are using this technique for communicating with USB protocol.

Like computer to communicate with ARM controller using USB. USB transfers the data in

different modes. First one is slow speed mode 10kbps to 100 kbps; second one is full speed

mode 500kbps to 10mbps, high speed mode 25mbps to 400 mbps. USB maximum cable length is

of 4 meters. Ex: Mouse, Keyboard, Hubs, switches, pen drive.

7.2.4 Differences between inter system protocols

7.3 Intra System Protocols

The Intra system protocol is used to communicate the two devices within the circuit board. While

using this intra system protocols, with out going to intra system protocols we will expand the

peripherals of the microcontroller. The circuit complexity and power consumption will be

increases by using intra system protocol. Using intra system protocols circuit complexity and

power consumption, cost is decrease and it is very secure to accessing the data.

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Intra System protocol block diagram

7.3.1 I2C Protocol

I2C stands for inter integrated circuit. I2C requires only two wires connecting all peripherals to

microcontroller.I2C requires two wires SDA (serial data line) and SCL (serial clock line) to carry

information between devices. It is a master to slave communication protocol. Each slave has a

unique address. Master device sends the address of the target slave device and read/write flag.

The address is match any slave device that device is ON, remaining slave devices are disable

mode. Once the address is match communication proceed between master and that slave device

and transmitting and receiving the data. The transmitter send 8-bit data, the receiver replies 1-bit

of acknowledgement. When the communication is completed master issues the stop condition.

The I2C bus was developed by Philips Semiconductors. Its original purpose is providing an easy

way to connect CPU to peripherals chips.

Peripheral devices in embedded systems are often connected to the microcontroller as memory

mapped devices. I2C requires only two wires for connecting all the peripherals to the

microcontroller.

These active wires, called SDA and SCL, are both bidirectional. SDA line is a serial data line

and SCA line is a serial clock line.

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I2C protocol clock signals

7.3.2 SPI Protocol

SPI stands for serial peripheral interface. It is one of the serial communication protocol

developed by Motorola. Some times SPI protocol is also called a 4-wire protocol. It requires four

wires MOSI, MISO, SS, and SCLK.SPI protocol used to communicate the master and slave

devices. The master first configures the clock using a frequency. The master then selects the

particular slave device for communication by pulling the chip select button. That particular

device is selected and starts the communication between master and that particular slave. The

master can select only one slave at a time. It is full duplex communication protocol. Not limited

to 8 bit words in the case of bit transferring.

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SPI protocol signals

7.3.3 CAN Protocol

CAN stands for controller area network .It is a serial communication protocol. It require two

wires CAN High (H+) and CAN low (H-). It was developed by the Robert bosh company in

1985 for in vehicle networks. It is based on a message oriented transmission protocol.

7.4 Microcontroller Communication with Computers

7.4.1 How is microcontroller interfaced to computers/ CPU?

The microcontroller is interfaced to microcontroller using serial port. A computer usually has

two serial ports and a parallel port. The serial ports denoting the transmitting and receiving port

are used for communication with the microcontroller through a RS232 standard cable. Usually a

level shifter IC Max232 is used as an intermediate between the RS232 cable and the

microcontroller.

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Microcontroller interfacing to Computer

7.4.2 RS232 Cable

Introduction

The RS-232(X) is a communication cable, commonly used for transferring and receiving the

serial data between two devices. It supports both synchronous and asynchronous data

transmissions. Many devices in the industrial environment are still using RS-232 communication

cable.

Rs-232 cable is used to identify the difference of two signal levels between logic 1 and logic 0.

The logic 1 is represented by the -12V and logic 0 is represented the +12V.

The RS-232 cable works at different baud rates like 9600 bits/s, 2400bits/s, 4800bits/s etc. The

RS-232 cable has two terminal devices namely Data Terminal Equipment and Data

communication Equipment. Both device will sends and receives the signals. The data terminal

equipment is computer terminal and data communication Equipment is modems, or controllers

etc.

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RS 232 Pin Description

RS232 Pin Diagram

It is a 25-pin connector, each pin has its own function is as follows.

PIN 1: (Protective Ground); It is a ground Pin.

PIN 2: Transmit Data.

PIN 3: Receive Data.

PIN 2 & PIN 3: These pins are most important pins for data transmitting and receiving. The 1 &

2-pins are used to data transmitting and pin-3 used to data receiving purpose.

PIN 4: Request to send.

Pin 5: Clear to send.

PIN 6: Data Set Ready.

PIN 20: Data terminal Ready.

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PIN 4, PIN 5, PIN 6, PIN 20: These pins are the handshaking pins(flow of control).Normally

terminals cannot transmit the data until clear to send transmission is received from the DCE.

PIN 7: This pin is the common reference for all signals, including data, timing, and control

signals. The DCE and DTE works properly across the serial interface and the pin-7 must be

connected both ends without interface would not work.

PIN 8: This pin also known as received line signal detect or carrier detect. This signal is

activated when a suitable carrier is established between the local and remote DCE devices.

PIN9: This pin is DTE serial connector; this signal follows the incoming ring to an extent.

Normally this signal is used by DCE auto answer mode.

PIN 10: Test Pin.

PIN 11: stand by select.

PIN 12: Data Carrier Detect.

PIN 13: Clear to send.

PIN 14: Transmit data.

PIN 15: Transmit clock.

PIN 17: Receive clock.

PIN 24: External Clock.

PIN 15, 17, 24; Synchronous modems use the signals on these pins. These pins are control bit

timing.

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PIN 16: Receive data.

PIN 18: Test Pin.

PIN 19: Request to send.

PIN 21: (Signal Quality Detector); This pin Indicates the quality of the received carrier signal

because the transmitting modem must be send 0 or either 1 at each bit time , the modem controls

the timing of the bits from the DTE.

PIN 22: (Ring Indicator): The ringing indicator means the DCE informs the DTE that the phone

is ringing. All the modems designed for direct connected to the phone network equipped with

auto answer.

PIN 23: Data Signal Rate Detector

7.4.3 Max232

Max 232 acts as a buffer driver for the processor. It accepts the standard digital logic values of 0

& 5 volts and converts them to the RS232 standard of +10 & -10 volts. Few Microcontrollers

have built in serial ports which allow for direct connection with the RS232 serial port of the PC.

However many microcontrollers give a 0 to 5V output and require a intermediate buffer circuit to

convert the 0 to 5 volts to +10 and -10V required by the RS232 port.

The Max 232 IC consists of two transmitter-receiver arrangement such that two serial ports can

be connected using the same chip. 5 capacitors of each 1microFarad are used to generate the

required RS232 standard voltage from the TTL/CMOS voltage. The transmitters convert the

TTL/CMOS level to RS232 level whereas the receiver receives the RS232 input and converts

them to TTL level voltage.

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Max 232 Pin diagram and block diagram

It is basically a 16 pin IC with the transmitter pins connected to the microcontroller and the port

such that the input transmitter pin get TTL input from the Microcontroller and the output

transmitter pin supply output to the RS232 port. The receiver pins are connected to the RS232

port such that the input receiver pin receive RS232 standard input from the PC port and the

output receiver pin supplies the TTL input to the Microcontroller.

Thus the transmitter takes input from the Microcontroller and gives output to the RS232 port

whereas the receiver takes input from the RS232 port and gives output to the Microcontroller.

The other pins are connected to 5 electrolyte capacitors such that one of the capacitors is used as

a voltage doubler to get +10V from 5Vs and another capacitor is used as a voltage inverter to get

-10V and the other three capacitors are used as bypass capacitors for Vcc, V+ and V- pins

respectively.

One of the basic advantages of Max 232 is that it operates with a 5V supply, which allows for a

single 5V supply to be used for both the IC and the Microcontroller.

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7.5 Summary

A microcontroller can communicate with devices on the same circuit board or devices on other

circuit board. When communicating with devices on the same circuit board, the communication

protocols used are called intra system protocols, example being I2C protocol. When

communicating with devices on different circuit board, the communication protocols used are

called inter system protocols, example being USB protocol. For a microcontroller to

communicate with a computer, R2C standard cables are used which is interfaced using Max232

level shifter IC.

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Chapter 8-Programming the Microcontroller

8.1 Introduction to programming a microcontroller

By the term programming a microcontroller, we refer to the set of instructions written and stored

in the microcontroller to carry out a particular task. These instructions or program can be written

using Assembly level language or C language.

8.2 Assembly Level Language Programming

8.2.1 8051 RAM Memory Structure

Assembly level programming is done in microcontrollers using registers. In 8051

microcontrollers, the RAM memory consists of 128Kbytes of memory space, addressed from

00H to FFH.

RAM structure

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00 to 1FH byte locations are used for 4 register banks. Each register bank consists of 8 bits and

stores temporary data. Register bank3 is also known as stack register. This temporary data can be

a byte of data or the address of that data.

20 to 2FH byte locations are bit addressable memory locations.

30 to 7FH are used as scratch pad RAM, used for reading/writing data.

80 to FFH are used for special purpose registers. These registers are the port registers(Port0,

Port1, Port2, Port3), SBUF and SCON registers(used for serial communication), TMOD, TCON

(used for timer and counter operations respectively), Accumulator(where the end result of any

execution is stored), PSW or flag register (used to select the register bank), DPTR(data pointer

register- used to store the address of the data) and PC (Program Counter Register- points to the

address of the instruction)

8.2.2 Assembly Level language coding

To write a program in microcontroller using assembly level language, we need to know about

instruction set and the addressing modes.

There are 4 addressing modes in 8051 microcontroller

Immediate Addressing mode- The immediate value of data is used, preceded by a ‘#’ sign.

Register Addressing mode- The register where the value is stored is used for any operation,

instead of the value itself.

Direct Addressing mode- The memory address of the value is used for operation directly. The

value stored in that memory address is executed upon or a value is send directly to the memory

address.

Register Addressing mode- Registers 0 and 1 can be used as pointers to data.

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An assembly level program consists of the following parts-

Label: - Defines a name or label for that particular instruction.

Directives- Directs any operation involving the operands. Examples are ORG, EQU, and END

etc

Mnemonics- Define the particular operation to be carried out. They are converted to Opcodes,

which are codes defining the instructions

Operands- Denote the values or registers upon which operation is carried out.

8.2.3 Steps in writing and executing a program

Writing and executing a program

Step1: Once a program is written on any editor using the assembly level language, it is

converted to machine level code by the assembler. Two files are created- a list file and an object

file.

Step 2- The object files are added together by the linker to form an absolute file.

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Step 3- This absolute file is then converted to hex file using object to hex converter.

Step 4- This hex file is burned into the ROM of the microcontroller. The ROM contains the

opcodes for each instruction.

Step 5- Once the microcontroller is powered up, it starts with 0000 location of ROM.

Step 6 - The instructions are executed one by one and program counter gets incremented

accordingly.

8.3 C Language Programming

Today, we can use many different programming languages such as C, JAVA, ORACLE and

others. These languages are called high level languages; to write the program in high level

language the programmer doesn’t need any knowledge on hardware which is used for high level

application development. The compiler plays a vital role in translating the high-level program to

machine level as the high level languages are used in native development.

8.3.1 Software used in microcontroller programming

The most popular software tool used for microcontroller programming is Kiel software. This

software is an integrated development environment (IDE) which is integrated with a text editor

to write programs, a compiler to convert the high level language to machine language.

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The uVision editors include all standard features like color syntax highlighting and quickly

identify the errors. The editor is available while debugging. The natural debugging environment

helps you quickly in identifying and correcting the errors in your program. After writing the

program in code editor save that file in .asm or .C format depending on which assembler you

have chosen.

8.3.1 How to use Kiel software to write microcontroller program

Guide to Start working with Keil Uvison:

1. Click on the Keil Vision Icon on Desktop.

The following steps involve in this process:

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Figure 1

2. Click on the Project menu from the title bar. Then click on New Project

Figure 2

3. Save the Project by typing suitable project name with no extension in your own folder sited

in either C:\ or D:\

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Figure 3

4. Then Click on save button above.

Select the component for u r project. i.e. Atmel……

Click on the + Symbols as for your requirement. Example here selected Atmel.

Figure 4

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5. Select AT89C51 as shown below

Figure 5

6. Then Click on “OK”

The Following steps involve in the above process:

Figure

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7. Then Click either YES or NO………mostly “NO”.

Now your project is ready to USE.

Now double click on the Target1, you would get another option “Source group 1” as shown in

next page.

Figure 7

8. Click on the file option from menu bar and select “new”

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9. The next screen will be as shown in text page

10. Now start writing program in either in “EMBEDDED C” or “ASM”.

For a program to be written in Assembly language, we must save it with an extension “.

Asm” and for “EMBEDDED C” based program we have to save it with extension “.C”

11. Now right click on Source group 1 and click on “Add files to Group Source”

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12. Now select as per your file extension given while saving the file.

Click only one time on option “ADD”.

Now Press function key F7 to compile. Any error will appear if so happen.

If the file contains no error, then press Control+F5 simultaneously.

13. Right click on the ‘target’ folder icon and select the ‘option for Target’ option.

14. A target window opens with a menu bar. Click on the ‘Target’ menu.

15. Set the crystal frequency for the microcontroller.

16. Click on the ‘Output’ menu. A window appears.

17. Click on the ‘create hex file’ button. A hex file is created.

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8.3.3 Steps in developing a microcontroller program using C language.

1. The program is written on the editor using the above given steps.

2. The program in high level language is converted to machine level language by the compiler. It

involves the formation of the list file and the object files.

3. The object files are linked together by the linker program to form the absolute file.

4. This absolute file is then converted to hex file by the Object to Hex converter.

8.4 Summary

Microcontroller 8051 is the most popular used series of microcontrollers for any simple

embedded system. It can be programmed using Assembly language program or high level

language like C. Once a program is written, it is converted to machine language and burned into

microcontroller hardware using any burner software.

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Chapter 9- Microcontroller Interfacing

9.1 Microcontroller interfacing with matrix keypad

9.1.1 What is a matrix keypad?

A keypad is the most widely used devices of digital circuits, microcontrollers or telephone

circuits. Many applications require large number of keys connected to a computing system.

Provided that it for the most part holds numbers then it can additionally be known as a numeric

keypad. In order to use it efficiently, we need a basic understanding of them. A matrix keypad

consists of arrangement of switches in matrix format in rows and columns with the

microcontroller I/O pins connected to the rows and columns of the matrix such that switches in

each row are connected to one pin and switches in each column are connected to another pin. A

keypad is generally a matrix arrangement of tact switches which are basically push button

switches.

9.1.2 How is matrix keypad interfaced to 8051 microcontroller?

Microcontroller interfacing to keypad

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From the circuit, pin 1.0 to pin 1.3 of port 1 of microcontroller are connected to rows of keypad

and pin 1.4 to pin 1.6 of port 1 of 8051 microcontroller are connected to columns of keypad.

When the numbers pressed in the matrix keypad load corresponding logical state at the input of

the microcontroller i.e., port 1. The program is so written that when say1111 is pressed then

microcontroller delivers a logic high command at the controller output. This output high logic

from the microcontroller is then fed to the relay driver IC input for ULN2003 output to go low to

switch ON the corresponding relay that in turn switches on the load as per the password sent

from the keypad. For example if 1111 is pressed the corresponding load 1 is switched ON and

while it is pressed again 1111 it switches OFF. Accordingly all other loads are operated as per

the passwords.

9.2 Motor interfacing to microcontroller

9.2.1 Introduction to LM293D- Motor driver IC

Microcontrollers can’t drive the motors directly. So we need some kind of drivers to control the

speed and direction of motors. The motor drivers will acts as interfacing devices between

microcontrollers and motors. Motor drivers will act as current amplifiers since they take a low

current control signal and provide a high current signal. This high current signal is used to drive

the motors. Using L293D chip is the easy way for controlling the motor using microcontroller. It

contains two H-bridge driver circuits internally.

This chip is designed to control two motors. L293D has two sets of arrangements where 1 set has

input 1, input 2, output1,output 2, with enable pin while other set has input 3, input 4, output 3,

output 4 with other enable pin.

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L293D has two set of arrangements where one set has input 1, input 2, output 1 and output 2 and

other set has input 3, input 4, output 3 and output 4, according to above diagram,

If pin no 2 and 7 are high then pin no 3 and 6 are also high. If enable 1 and pin number 2 are

high leaving pin number 7 as low then the motor rotates in forward direction.

If enable 1 and pin number 7 are high leaving pin number 2 as low then the motor rotates in

reverse direction.

9.2.2 How is motor interfaced to 8051 microcontroller?

As said above, a motor is interfaced to the microcontroller through a motor driver IC.

Microcontroller interfacing to motor

Three pins of port 1 of the microcontroller are connected to the input pins and enable pin of the

motor driver IC. These pins are the output pins of the microcontroller. The motor driver IC

operates drives a motor only when a high logic signal is applied to its enable input. Therefore

when pin of microcontroller goes high and the two input pins of the motor driver goes high or

low alternatively, the motor starts rotating in forward or reverse direction accordingly.

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9.3 Relay interfacing to 8051 microcontroller

9.3.1 Introduction to Relay Drivers

A relay coil requires about 12V to be energized, whereas the output pin of the microcontroller is

at TTL logic level (about 5V). For this reason a driver is needed to act as an interface between

the microcontroller and the relay. This relay driver can be a MOSFET or a relay driver IC

ULN2003

9.3.2 Interfacing relay with microcontroller using relay driver IC ULN2003

A relay driver IC ULN2003 is a 16 pin IC. It is a high voltage IC consisting of 7 Darlington

pairs of transistors. It consists of 7 input pins and 7 corresponding output pins. In other words it

can drive 7 relays.

Microcontrollers interfacing with relay using ULN2003

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Here pin of microcontroller is connected to input pin 1B of the microcontroller. When this input

goes high, i.e. a pulse is given to this pin; the output pin 1C of the driver goes low, i.e. connected

to ground. This output pin is connected to the relay such that current flows through the relay coil

and it gets energized.

9.3.3 Interfacing relay with microcontroller using transistor

A transistor can also be used as a relay driver. The basic idea is to use the switching operation of

the transistor.

One end of the relay coil is connected to 12V supply, whereas other end is connected to the

collector of the transistor. Base terminal of that transistor is connected to the output pin of the

microcontroller. When a pulse is applied to this pin, the transistor gets switched ON, the

collector and emitter terminals are shorted and get connected to ground. Current flows through

the relay coil and coil is energized.

9.4 16 by 2 LCD display interfacing to microcontroller

Many microcontroller devices are using smart LCD displays to output visual information. For an

8-bit data bus, the display requires a +5V supply plus 11 I/O lines. A 4 bit data bus requires

supply line as well as 7 extra lines. When the LCD display is not enabled, data lines are tri-state

which means they are in a state of high impedance and this means they do not interfere with the

microcontroller operation when display is not used.

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LCD interfacing to microcontroller

The three control lines are referred to as EN, RS and RW.

The EN (Enable) control line is used to send the data to the LCD. A high to low transition at

this pin will enable the module.

When RS or Register Select is low, the data is to be treated as a command instruction. When

RS is high, the data being sent is displayed on the screen. For Instance, to display any

character on the screen, we set RS high.

When RW or Read/Write Control line is low, the information on the data bus is being written

to the LCD. When RW is high, the program is effectively reading the LCD. RW line will

always be low.

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The data bus consists of 4 or 8 lines; it depends on the mode of operation selected by the user.

The lines of an 8 bit data bus are referred to as DB0, DB1, DB2, DB3, DB4, DB5, DB6 and

DB7.

9.5 Summary

Microcontrollers can be interfaced to many devices like motors, relays, displays etc. Interfacing a

microcontroller with input or output devices is necessary for proper functioning of any

embedded system. Devices like motors, relays are interfaced using a driver IC, where as keypad

and displays are interfaced directly.

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Chapter 10- Designing your own microcontroller based

projects

10.1 Step by step guide to build your own microcontroller based

projects

10.1.1 Introduction and theory about the project

I am sure there must be many of you, who would love to build your own embedded system or let

me say a simple project using a microcontroller. Now for this, you need to have a basic idea

about each step required to develop a microcontroller based project. So here I am explaining the

basic steps to build a microcontroller based project.

But before that, let us get an idea about the project we would like to design and the theory behind

it.

Aim of the project

To design a LED flash light system using Microcontroller

Theory

The LED flash light system can produce the light through light emitting diode. The incandescent

lights used in traditional flash light consume more energy and have very less life time. The LED

lights on the other hand, consume less energy and have long life.

Basic Idea behind the Design

The microcontroller generates the output logic pulses so that the LED light is switched ON and

OFF at certain intervals. It is a 40 pin microcontroller. The Crystal interfaced to input pins of the

microcontroller provide accurate clock signals at the crystal frequency.

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10.1.2: Step1- Circuit Designing

The 8051 microcontroller crystal operates at 11.0592 MHz frequencies because it can give exact

clock pulses for data synchronizing. Two capacitors are connected to the crystal oscillator with

range of 20pf to 40pf which is used to stabilize the clock signals. The 8051 microcontroller at

some times goes to block state or missing time calculation.

At that time we need to reset the microcontroller. When the microcontroller is reset, it takes

maximum 3sec time delay with the help of the 10k resistor and 10uf capacitor.

Circuit Components:

Hardware Components:

Yellow LED

Crystal

Reset

8051 microcontroller

Capacitors

Resistors

Software Components:

Keil compiler

Proteus software

Embedded C language

Circuit Connections

The 5v DC supply is given to the 40 pin of the microcontroller which drives the circuit. The

crystal is connected to the 18 and 19 pin of the microcontroller.

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The reset circuit is interfaced at 9 pin of the microcontroller. The Yellow LED is connected to

the pin P0.2 of the microcontroller.

10.1.3 Step 2: Microcontroller Program Coding

First open the Kiel uVison2 software. This shows the menu bar with file, edit, view, project

and tools option.

Select the project option and select the ‘new project option’ from the drop down menu. Give

a name to the project and click on ‘save’ button to save the project. A folder named ‘target’ is

created.

Select a microcontroller for your project. Here I am selecting ‘Atmel’. Select the exact type

of Atmel microcontroller from the drop down menu. Here 89C51 microcontroller is selected.

A folder with the name ‘source group’ is created in the ‘target’ folder.

Click on the ‘File’ menu on the menu bar. Select ‘new file’ from the drop down menu.

Kiel Window

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Write the code on the blank space.

The LED Flash Light program:

#include<reg51.h>

sbit LED= P0^2;

void delay( unsigned int a);

void main()

{ LED=0;

While (1)

{ LED=0;

delay(600);

LED=1;

delay(600);

}

}

void delay (unsigned int b)

{ unsigned int k;

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for(k=0;k<b;k++);

}

Save this code with ‘.C’ extension.

Right click on the ‘source group’ folder icon and select ‘add files to group’ option.

A window appears. Select the ‘C’ file to be added.

Select the ‘debug’ menu. It checks the program for any errors.

Right click on the ‘target’ folder icon.

Select the ‘option for Target’ option.

A target window opens with a menu bar. Click on the ‘Target’ menu.

Set the crystal frequency for the microcontroller.

Click on the ‘Output’ menu. A window appears

Click on the ‘create hex file’ button. A hex file is created.

10.1.4: Step 3: Circuit Drawing

This is circuit is designed with help of Proteus software. It is circuit design software which

contains a database of components which we can use to build the circuit. Each and every

component is available in the components library.

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Proteus window using the circuit

Open the Proteus software. A window with a menu bar appears.

Click on the file menu.

Select ‘new design’ from the drop down menu.

Click on the library menu.

Select ‘pick devices/symbol’ from the drop down menu.

Select the relevant comment by double clicking on it, so that the component appears on the

window.

Add all the components and draw the circuit with proper connections.

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Circuit Diagram

10.1.5: Step 4: Code Dumping

Loading the code to the microcontroller is called dumping. The microcontrollers understand only

binary language. So we need to load the hex code into the microcontroller. There are lots of

softwares available in the market for loading the code to the microcontroller. Here I am using

‘Willer’ programmer software to dump the code to the 8051 microcontroller. The programmer

kit comes with software along with the hardware kit.

This software needs to be installed onto the computer. The hardware kit comes with a socket, on

which the microcontroller is placed. Here are the steps to load the code onto the microcontroller.

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Willer Programmer hardware kit

Willer software window

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The hardware (programmer kit) is interfaced to the computer through a serial cable

The microcontroller is placed on the socket of the hardware kit. Press the lock button to

ensure the microcontroller is connected to the board.

Open the software installed in the computer. It will display some operating modes.

Select any mode. A window with a menu bar appears.

Click on the ‘file’ menu and select ‘load file’ option from the drop down menu

Click on the ‘auto’ button so that the hex file is loaded to the microcontroller.\

10.1.6: Step 5: Simulating the Circuit

Open the project in the proteus software.

Click on the ‘Debug’ menu.

Select the ‘start debugging’ option. The LED starts blinking, which indicates the circuit is

running.

After some time, select the ‘stop debugging’ option. The LED will now stop blinking.

10.2 Few Microcontroller based projects

10.2.1 Controlling loads using Microcontroller

This project is developed to demonstrate controlling of electrical appliances using

Microcontroller, based on control signals from cell phone. The basic idea involves converting the

tone signals generated by pressing any number on the cell phone, to pulses which are given to the

microcontroller to switch on or off the loads.

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Controlling loads using microcontroller

The mobile phone audio socket is connected to a decoder. When a call is received by the phone

or a number is pressed on the phone, the generated tone signal is decoded by the decoder to

obtain the electric signal in parallel form. The microcontroller receives this parallel data input at

one of its port. It is programmed such that it further processes the input to get the required load

number. Each output pin corresponds to a particular load. A relay driver IC is interfaced to

another port of the microcontroller. The microcontroller output is given to this relay driver and

based on the particular input pin of the relay driver IC going high, the corresponding output pin

goes low and the relay is energized. The particular load gets the supply and gets switched ON.

10.2.2 Motor Speed Control using Microcontroller

This project is designed to achieve speed control of a brushless DC motor by using a

microcontroller. The idea involves giving input to the microcontroller to increase or decrease the

speed and sensing the speed of the motor to achieve the desired speed.

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Motor speed control using microcontroller

Two push buttons are interfaced to pins of one of the port of the microcontroller. These push

buttons are used to set the desired speed of the motor. An optoisolator is also interfaced to the

microcontroller. When the microcontroller pin connected to the optoisolator goes low, the motor

driver (A MOSFET in this case) starts conducting and the motor starts rotating (as it gets proper

supply). A speed sensor arrangement consisting of IR LED and phototransistor is used which

senses the speed of the motor. The microcontroller is programmed such that on receiving an

interrupt signal from the sensor, it generates pulse width modulated signals to the optoisolator, to

achieve the desired speed of the motor.

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10 .2.3 GSM based monthly energy meter billing using Microcontroller

This project defines a system wherein the energy units calculated by the energy meter are sent by

the microcontroller through a GSM modem to the concerned power distribution department.

GSM based monthly energy meter using microcontroller

An energy meter is connected to an OPTO-isolator such that the number of energy units causes

the generation of a fixed number of light pulses by the

OPTO- LED. The output of this OPTO isolator is given to the microcontroller, such that a

certain number of pulses received at the input pin are considered to be one unit. The

microcontroller is programmed such it counts the number of pulses and accordingly counts the

number of units. A GSM modem is interfaced through a level shifter IC to the serial port pins of

the microcontroller. The number of units consumed is transmitted to the concerned number

through the GSM modem.

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10.2.4 Automatic Dialing to any telephone on detecting burglary

A system is developed which achieves automatic detection of burglary and instantly sends an

alert intimation to an authorized number. This whole operation is done by a microcontroller

wherein the detection is done by a hidden switch and a keypad interfaced to the microcontroller

is used to enter the authorized number.

Automatic dialing to any phone on burglary detection

A push button is interfaced to the interrupt pin of the microcontroller such that when it is pressed

(detecting the burglary), the microcontroller gets an interrupt signal. The microcontroller is

programmed such that on receiving the interrupt signal, it generates a parallel data output at one

its port. This parallel data corresponds to the number stored in the external memory of the

microcontroller. This data in parallel form is encoded to generate a tone signal which is inserted

into the telephone line by a relay.

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10.3 Few Microcontroller based circuits

10.3.1 Lamp switching using PIC Microcontroller

Lamp Switching using microcontroller

The circuit below consists of a lamp whose switching is controlled using a PIC microcontroller.

The Microcontroller is interfaced with an external crystal which provides clock input. The PIC is

also interfaced with a push button and on pressing the push button, the Microcontroller

accordingly sends a high signal to the base of the transistor, so as to switch on the transistor and

thus give proper connection to the relay to switch it on and allow passage of AC current to the

lamp and thus the lamp glows. The status of the operation is displayed on the LCD interfaced to

the PIC microcontroller.

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10.3.2 Programmed Message Sending Circuit

Programmed message sending circuit

On instruction from the LCD display, the mobile number is entered through the keypad and is

stored in the appropriate memory location. After that a number between 1 and 9 is entered

through the keypad and the Microcontroller accordingly sends the message corresponding to that

number.

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The message is send to the GSM modem through the RS 232 connector and the level shifter IC

arrangement which transmits the message to the given mobile number. The whole operation is

accordingly displayed on the LCD display.

After some time, the message “ GSM based message sending System” Is displayed and when

program button is entered, the display changes to the message-“Enter mobile number” After

entering the mobile number # is pressed that prompts to enter the message number. After putting

the message number and then # pressed again indicates that “message sending” and then displays

“message sent” after sometime and then resumes back to normal display.

If you are not getting any of these message means that SIM card is not getting signal / network

not available.

Standard power supply of 12 volt DC and 5 volt through a regulator are made from a step down

12 v transformer along with a bridge rectifier and filter capacitor.

10.3.3 Intra system communication in automobiles

In this application, we follow a CAN (Control Area Network) concept, generally used in cars,

automobiles and industries. As the name implies control area network means that microcontroller

is connected in a network fashion like computers so that it can exchange data among themselves.

Here we are using 2 microcontrollers connected in a network fashion by a pair of wire connected

to pin 10 and 11(i.e., P3.0, P3.1) of port 3 of each microcontroller pins for the transmission and

reception of data among themselves with the help of RS232 serial communication using a pair of

wire. The first microcontroller is interfaced to 4×3 matrix keypad, which is connected to input

ports of first microcontroller. The second microcontroller is interfaced to an LCD display to

receive data from the first microcontroller. A 16 by 2 LCD is used to display 16 characters in

two lines.

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Intra system communication in automobiles using microcontrollers

For each microcontroller, separate program is written in C. The hex files of it are burnt on to the

respective microcontroller. When we apply power to the circuit then the LCD displays a message

WAITING which means it is waiting for some data. For example a password as 1234, when 1 is

pressed from keyboard then LCD displays 1 and when 2 is pressed it displays 2 and same for 3

but when 4 is pressed from keyboard they are all displayed and data communication takes place

through the Rx and Tx pair.

10.4 Summary

Microcontroller is the main component in any embedded system. To build a simple embedded

system or a microcontroller based project, one has to first design the circuit, draw the circuit on

any simulation software. The program is to be written using any software like Kiel and then the

program is to be loaded onto the microcontroller using software. By following this simple

procedure, it is possible to build many simple microcontroller based projects and circuits.

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Ending Stuff

About the authors

The credit for each and every information given in this book goes to the team of Edgefx. We the

team of Edgefx , have been the pioneers in providing technical solutions and project kits to

millions of engineering students around the globe, since 1997. The credit for the projects and the

circuits goes to the technical team of Edgefx.

Right to readers

This book is intended to give relevant knowledge about microcontrollers, to the readers in the

simplest and basic way. Any person interested in this book has the authority to download, reprint

and distribute this book. However no person is given the permission to make any modifications

or alternations to the book and use it for his/her own monetary profit.

Legal Info

The copy right for the content and few images is solely authorized to the team of Edgefx. The

information written in each and every chapter is written based on relevant research and inputs by

the team of authors. The projects and circuits mentioned in the last chapter are the properties of

Edgefx team and are fully tested and authenticated.

Ways to interact with the team

If you are engineering student, looking for projects, feel free to click on the link given below:-

http://www.edgefxkits.in

111

If you want to look for technical solutions and information on any topic relevant to electronics,

electrical, robotics and communication, click on the link given below:-

http://www.elprocus.com/

You can also contact us at social media by liking our facebook pages

https://www.facebook.com/edgefx

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