1. INTRODUCTION TO EMBEDDED SYSTEMS

An embedded system is a special-purpose system in which the computer is completely encapsulated

by the device it controls. Unlike a general-purpose computer, such as a personal computer, an

embedded system performs pre-defined tasks, usually with very specific requirements. Since the

system is dedicated to a specific task, design engineers can optimize it, reducing the size and cost of

the product. Embedded systems are often mass-produced, so the cost savings may be multiplied by

millions of items.

Physically, embedded systems range from portable devices such as digital watches and MP3 players,

to large stationary installations like traffic lights, factory controllers. Complexity varies from low,

with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted

inside a large chassis or enclosure.

Embedded systems contain processing cores that are either microcontrollers or digital signal

processors (DSP). The key characteristic, however, is being dedicated to handle a particular task.

Since the embedded system is dedicated to specific tasks, design engineers can optimize it to reduce

the size and cost of the product and increase the reliability and performance. Some embedded systems

are mass-produced, benefiting from economies of scale.

Robotics and automation are a part of embedded systems itself. Robot development and automation

needs study of embedded systems.

Examples of Embedded System:-

I. automatic teller machines (ATMs)

II. avionics, such as inertial guidance systems, flight control hardware/software and other

integrated systems in aircraft and missiles

III. cellular telephones and telephone switches

IV. computer equipment such as routers and printers

V. engine controllers and antilock brake controllers for automobiles

VI. home automation products, like thermostats, air conditioners, sprinklers, and security

monitoring systems

VII. handheld calculators

VIII. household appliances, including microwave ovens, washing machines, television sets

IX. medical equipment

X. handheld computers

XI. videogame consoles

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2.SOFTWARE DEVELOPEMENT

2.1 ECLIPSE

2.1.1 INTRODUCTION

Developing programs using a text editor such as TextPad is simple and straightforward.While such

editors allow students to begin programming with a minimum of distractions, asprograms become

larger and more complicated, a more sophisticated tool for developingprograms is quite valuable. In

this chapter, we examine one particular tool for developinglarge programs, the Eclipse system. Eclipse

can be used to develop programs in Java and inC/C++ (plus various other languages as well). In this

chapter, we examine how to install Eclipse.

2.2 INTERACTIVE DEVELOPMENT ENVIRONMENTS

Interactive development environments (IDE) provide a wealth of features to support the programmer

that are not available in a simple editor. There are many IDE’s currently available, some are shareware

and some must be purchased and are often expensive. Most IDE’s provide similar facilities, such as

the ability to view different classes at the same time, debuggers that step through a program line-by-

line in order to assist in locating errors, etc. One of the newest and most popular IDE’s is the Eclipse

IDE which is available at no cost from the Eclipse website (http://www.eclipse.org/).

2.3 THE ECLIPSE IDE

Eclipse is an IDE (actually it is more than an IDE but we will concentrate on Eclipse as an IDE) that

was initially controlled by IBM but then IBM released the source code for Eclipse, making the project

open source. Eclipse development is taking place in several cities, including Winnipeg, Ottawa, and

Zurich, although there is also a large community of programmers who provide extensions to Eclipse in

order to improve the Eclipse environment. The facilities in Eclipse can be extended by defining “plug-

ins” which provide additional features or support additional languages.. Eclipse runs on most

operating systems, including Unix, Linux, Windows, and Mac OS X.

[2]

2. 4 TINA PRO :-

THE COMPLETE ELECTRONICS LAB FOR WINDOWS

INTRODUCTION:-TINA is a powerful yet affordable software package for designing,

simulating and analyzing electronic circuits. It works equally well with linear and nonlinear analog

circuits, digital and mixed circuits. Analysis results can be displayed as sophisticated diagrams or on a

range of virtual instruments. Comprehensive DTP tools and powerful text and equation editors can be

used to produce professional reports and presentations. The standard library contains over 20000

components and can be extended by the user. Electronics engineers will find TINA an invaluable, easy

to use and high performance

tool. TINA can also be used in the training environment. It includes unique tools for testing students’

knowledge, monitoring progress and introducing troubleshooting techniques. With optional hardware

it can be used to test real circuits for comparison with the results obtained from simulation. Of great

importance to educators, the package includes all the tools needed to prepare

educational materials. The circuit diagrams and the calculated or measured results can be printed or

saved to files in standard Windows WMF format. These output files can be processed by a number of

well known software packages (Microsoft Word, Corel Draw etc.). Net lists can be exported and

imported in Pspice format and also to drive popular PCB packages such as ORCAD, TANGO, PCAD,

PROTEL, REDAC and EDS.

TINA has special operating modes for training and for examination. In these modes, under TINA’S

control, the students solve problems assigned by the teacher. The solution format depends on the types

of problems: they can be selected from a list, calculated numerically, or given in symbolic form. The

interpreter - providing a number of solution tools - can also be used for problem solving. If the student

cannot solve the problem, he/she can turn to the multi-level Advisor. The package includes all the

tools needed to produce educational materials. A collection of examples and problems worked out by

teachers is also part of the package. Another special educational function of TINA is the software or

hardware simulation of circuit faults to practice troubleshooting. Using TINA, you can transform

existing PC classrooms into contemporary electronics training labs at low cost.

[3]

THE BASIC SCREEN FORMAT:-

1. The menu bar

2. The cursor or pointer

3. The Schematic window

4. The Tool bar

5. The Component bar6. Find component tool7. Open files tab8. The TINA Task bar9. The Help line

3.PCB DESIGNING

3.1 INTRODUCTION:-

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PCB Stands for "Printed Circuit Board." A PCB is a thin board made of fiberglass, composite epoxy,

or other laminate material. Conductive pathways are etched or "printed" onto board, connecting

different components on the PCB, such as transistors, resistors, and integrated circuits.

PCBs are used in both desktop and laptop computers. They serve as the foundation for many internal

computer components, such as video cards, controller cards, network interface cards, and expansion

cards. These components all connect to the motherboard, which is also a printed circuit board.

While PCBs are often associated with computers, they are used in many other electronic devices

besides PCs. Most TVs, radios, digital cameras, cell phones, and tablets include one or more printed

circuit boards. While the PCBs found in mobile devices look similar to those found in desktop

computers and large electronics, they are typically thinner and contain finer circuitry.

HISTORY :

The inventor of the printed circuit was the Austrian engineer Paul Eisler (1907–1995) who,

while working in England, made one circa 1936 as part of a radio set. 

MATERIAL:

Conducting layers are typically made of thin copper foil. Insulating layers dielectric are

typically laminated together with epoxy resin  prepreg. The board is typically coated with  a solder

mask that is green in color. Other colors that are normally available are blue and red. There are

quite a few different dielectrics that can be chosen to provide different insulating  values depending

on the requirements of the circuit. Some of these dielectrics are polytetrafluoroethylene (Teflon),

FR-4,  FR-1, CEM-1 or CEM-3. Well known prepreg materials used in the PCB industry are FR-2

(Phenolic cotton paper), FR-3 (Cotton paper and epoxy), FR-4 (Woven glass and epoxy), FR-5

(Woven glass and epoxy), FR-6(Matte  glass and polyester), G-10(Woven glass and epoxy), CEM-

1 (Cotton paper and epoxy), CEM-2 (Cotton paper and epoxy), CEM-3 (Woven glass and 

epoxy),CEM-4 (Woven glass  and epoxy), CEM-5 (Woven glass and polyester).

Thermal expansion is an important consideration especially with BGA and naked die technologies,

and glass fiber offers the best dimensional stability.

3.2 TYPES OF PRINTED CIRCUIT BOARDS

Single Sided Board:-This is the least complex of the Printed Circuit Boards, since there is only a

single layer of substrate. All electrical parts and components are fixed on one side and copper traces

are on the other side.

Double Sided Board:-This is the most common type of board, where parts and components are

attached to both sides of the substrate. In such cases, double-sided PCBs that have connecting traces

on both the sides are used. Double-sided Printed Circuit Boards usually use through-hole construction

for assembly of components.

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Multi Layered Board:-Multi layered PCB consists of several layers of substrate separated by

insulation. Most common multilayer boards are:  4 layers, 6 layers, 8 layers, and 10 layers. However,

the total number of layers that can be manufactured can exceed over 42 layers. These types of boards

are used in extremely complex electronic circuits.

3.3 PCB DESIGN STEPS IN OrCad 10.5

3.3.1 ENTRY OF SCHEMATIC DIAGRAM

Schematic diagram provides the functional flow and the graphical representation of an electronic

circuit. The entry of schematic diagram is the first step in PCB design using OrCad.

A schematic diagram consists of:-

Electrical connections(nets)

Junctions

Integrated circuits symbols

Discrete components symbols like resistors, capacitors etc.

Input / output connectors

Power and ground symbols

Buses

No connection symbols

Components reference names

Text

3.3.2 THE SCHEMATIC PAGE EDITOR:

The schematic page editor is used to display and edit schematic pages. So that one can parts; wires;

buses and draw graphics. The schematic page editor has a tool palette that you can use to draw and

place everything you need to create a schematic page. One can print from within the schematic page

editor, or from the project window.

[6]

Fig 7.1 Schematic Page Editor

3.3.3 THE PART EDITOR:

The part editor is used to create and edit parts.

From the view menu of the part editor you can choose either part or package. In part view one can:-

Create and edit parts and symbols, then store in new or existing libraries.

Create and edit power and ground symbols, off-page connector symbols, and title block

Use the tool palette’s electrical tools to place pins on parts, and its drawing tools to draw parts

and symbols.

3.3.4 THE SESSION LOG:

The session log lists the events that have occurred during the current Capture session, includes

message resulting from using capture’s tools. To display context-sensitive help for an error message,

put the cursor in the error message line in the session log press F1.The ruler along the top appears in

either inches or mill meters, depending on which measurement system is selected in the window panel.

Your tab setting are saved and used each time you start capture.

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Fig 7.2 Session Log window

One can search for information in the session log using the find command on the Edit menu. You can

also save the contents of the of the session log to a file, which is useful when working with Orcad’s

technical support to solve technical problems. The default filename is SESSION.TXT.

3.3.5 THE TOOLBAR:Capture’s toolbar is dock able (that means you can select and drag the

toolbar to new location) as well as resizable, and displays tool tips for each tool; by choosing a tool

button you can quickly perform a task. If tool button is dimmed, you can’t perform that task in the

current situation.

Fig 7.3 Toolbar

Some of the tools operate only on what you have selected, while others give you a choice of either

operating on what is selected or expanding the scope to entire project.

You can hide the toolbar, then display it again when u need it. For hiding select from the schematic

page editor’s view menu, choose TOOLBAR.

3.3.6 THE TOOL PALETTE:Capture has two tool palettes: one for the schematic page editor and

one for the part editor. Both tool palettes are dock able and resizable. They can also display tool tips

that identify each tool. The drawing tools on the two tool palettes are identical, however, each tool

palette has different electrical tools after you choose a tool, and you press the right mouse button to

display a context- sensitive pop-up menu.

[8]

3.3.7 THE SCHEMATIC PAGE EDITOR TOOL PALETTE:

The first group of tools on the tool palette is electrical tools, used to place electrical connectivity

objects. The second group of tools is

Drawing tools, used to create graphical objects without electrical connectivity.

Fig7.4 schematic page editor tool palette

3.3.8 THE PART EDITOR TOOL PALETTE:

The first group of tools on the part palette is electrical tools, used to place pins and symbols. They

have been already explained above within the schematic page editor tools. The second group of tools

is drawing tools, used to create graphical objects without objects any electrical connectivity and is

described:

Pin Tools: Place pins on part

Pin Array: Place multiple pins on part

3.4 CREATING NET LIST FILE

Net-list file is a document file which contains information about the logical interconnections between

signals and pins. Before one create a net list file, be sure one’s project is completed, annotated and it is

free from electrical rule violations.

A net list file consists of nets, components, connectors, junctions, no connection symbol, power and

ground symbols.

3.4.1 CREATION OF NET LIST IN CAPTURE:

Select your design in the project manager.

From the tools, choose create net list. The net list dialog box displays.

Choose a net list format tab.

If necessary, set the part value and PCB foot print combined property strings to reflect the

information you want in the net list.

Click ok to create the net list.

In the net list file text box, enter a name for the output file. If the selected format creates an

additional file, enter its file name in the second text box.

3.5 LAYOUT PLUS

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Layout plus is one part for the PCB design in which we place as well as route the components an set

unit of measurement, grids, and spacing in OrCad. Within other soft wares you also have to place and

route the components in similar way. For the placement and routing of the components we normally

use auto-placement and auto-routing. Unfortunately, in a lot of soft wares some critical signals have to

be routed manually before auto-routing. In layout plus we also define the layer stacks, pad stacks and

via's.

3.5.1 STEPS FOR BOARD DESIGN:

At first, we have created a net list from our schematic diagram by using capture.

Layout plus includes design rules in order to guide logical placement and routing. That means,

load the net list into layout to create the board. At the same time you have to specify the board

parameters.

Specify board parameters: Specifying global setting for the board, including nits of

measurements, grid, and spacing

Place components: Use the components tool in order to place manually the components which

are fixed by the system designer on the board or otherwise use auto-placement.

Route the board: Use different routing technologies to route the board and take advantage of

push and shove (a routing technology), which moves track you are currently routing as well as

you can also auto route the board.

Provide finishing of the board: Layout supplies an ordered progression of commands on the

auto menu for finishing your design. These commands include design rule check, cleanup

design, rename components, back annotate, run post processor, and create reports.

3.5.2 THE DESIGN WINDOW:

The design window provides a graphical display of printed circuit board, it is primary window you use

when designing your board. It also provides tools to facilitate the design process such as to update

components and design rule violation.

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Fig 7.5 design window

3.5.3 MAIN WINDOW:

Method to create a board with Layout Plus:

Ensure that net list with all footprints and necessary information has been created.

Create a directory in which the schematic design, net list, and boar will co-exit and put the

schematic design and net list. OrCad provides a directory for this purpose.

From the layout session frame’s file menu, choose New. The load template file in the dialog

box displayed.

Fig 7.6 main window

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3.5.4 DESIGN STEPS:

Select the technology template (.TCH), then choose the open button and load the net list in

other box.

Then apply the auto ECO.

If necessary, respond to link footprints to component dialog.

Draw the board outline by using the obstacle tool in the tool bar.

3.5.5 SETTING BOARD PARAMETERS:

There is some parameter which should be set before placing the components on board. They are as

follows:-

Set Datum

Create a board outline

Set units of measurements

Set system grid

Add mount holes

3.5.6 CREATING OF BOARD OUTLINE:

Board outline is the graphical representation of the size of the actual PCB board. So it is the main step

in layout, to draw the board outline of the actual size of PCB board.

3.5.7 PLACEMENT OF COMPONENTS:

Placement of components means that to place the components in designed box. A designer should

follow the following steps before going for it:-

Optimize the board for component placement.

Load the placement strategy file.

Place components on the board.

Optimize placement using various placements

Components can be placed by using two techniques:-

1) Manual placement of components

2) Auto placement of components

Choose the components tool bar button. From the pop up men, choose the queue for placement. The

components selection criteria dialog box appears. Enter the reference designator of the components

that you want to place in the appropriate text box, and click ok. Drag the components to desired

location, place it there.

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3.5.8 CONDUCTOR ROUTING IN LAYOUT:-

After placing all the components the other main step is to route the board from the electrical

connections between the components. One may route board manually or automatically by auto router.

100% auto routing can be achieved only when components are placed in the order of functional flow

of electronic circuit. The main routing tool available in OrCad is as flow:-

Add/edit route mode

Edit segment mode

Shove track mode

Auto path route mode

3.5.9 DESIGN RULE CHECK:-

In manual designs every thing was checked as a possible source of error. Components sizes, hole

sizes, conductor widths and clearance, land-to-hole-ratio, board areas to be free of components,

clearance to the edges, positional accuracy and of course electrical interconnections had tad to be

personally reviewed with a great deal of care. After completing the design of printed circuit board with

the help of an EDA-Tool, a designer has again to verify the PCB in order to find out errors.

[13]

4.THE 8051 MICROCONTROLLER4.1 INTRODUCTION

The microcontroller incorporates all the features that are found in microprocessor. The microcontroller

has built in ROM, RAM, Input Output ports, Serial Port, timers, interrupts and clock circuit. A

microcontroller is an entire computer manufactured on a single chip. Microcontrollers are

usually dedicated devices embedded within an application. For example, microcontrollers are used as

engine

controllers in automobiles and as exposure and focus controllers in cameras. In order to serve these

applications, they have a high concentration of on-chip facilities such as serial ports, parallel input

output ports, timers, counters, interrupt control, analog-to-digital converters, random access memory,

read only memory, etc. The I/O, memory, and on-chip peripherals of a microcontroller are selected

depending on the specifics of the target application. Since microcontrollers are powerful digital

processors, the degree of control and programmability they provide significantly enhances the

effectiveness of the application. The 8051 is the first microcontroller of the MCS-51 family

introduced by Intel Corporation at the end of the 1970s. The 8051 family with its many enhanced

members enjoys the largest market share, estimated to be about 40%, among the various

microcontroller architectures. The microcontroller has on chip peripheral devices. In this unit

firstly we differentiate microcontroller from microprocessor then we will discuss about Hardware

details of 8051 and then introduce the Assembly level language in brief.

MICROCONTROLLERS

Microcontroller (MC) may be called computer on chip since it has basic

features of microprocessor with internal ROM, RAM, Parallel and serial

ports within single chip. Or we can say microprocessor with memory and

ports is called as microcontroller. This is widely used in washing machines,

vcd player, microwave oven, robotics or in industries.

Microcontroller can be classified on the basis of their bits processed like

8bit MC, 16bit MC.

8 bit microcontroller, means it can read, write and process 8 bit data. Ex.

8051 microcontroller. Basically 8 bit specifies the size of data bus. 8 bit

microcontroller means 8 bit data can travel on the data bus or we can read,

write process 8 bit data.

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4.2 MICROCONTROLLER FAMILIES

8051- These microcontrollers are old but still trendy and most of the companies fabricate these

microcontrollers. The older types of 8051 have 12 clocks per instruction that make it sluggish whereas

the recent 8051 have 6 clocks per instruction. The 8051 microcontroller does not have an in built

memory bus and A/D converters. In 1980, Intel fabricated the single chip microcontroller 8051 with

Harvard architecture.

PIC- Programmable Interface Controller is usually referred as PIC. They are slightly older than 8051

microcontrollers but excel cause of their small low pin count devices. They perform well and are

affordable.  The Microchip technology fabricated the single chip microcontroller PIC with Harvard

architecture. The programming part is very tedious and hence it is not recommended for beginners.

AVR(Advanced Version RISC) - In 1996, Atmel fabricated this single chip microcontroller with a

modified Harvard Architecture. This chip is loaded with C- compiler, Free IDE and many more

features. This microcontroller is a bit difficult for the starters to handle.

4.3 DIFFERENCE BETWEEN MICROCONTROLLER AND MICROPROCESSOR:-

It is very clear from figure that in microprocessor we have to interface additional circuitry for

providing the function of memory and ports, for example we have to interface external RAM for data

storage, ROM for program storage, programmable peripheral interface (PPI) 8255 for the Input Output

ports, 8253 for timers, Sartor serial port. While in the microcontroller RAM, ROM, I/O ports, timers

and serial communication ports are in built. Because of this it is called as “system on chip”. So in

micro-controller there is no necessity of additional circuitry which is interfaced in the microprocessor

because memory and input output ports are inbuilt in the microcontroller. Microcontroller gives the

satisfactory performance for small applications. But for large applications the memory requirement

is limited because only 64 KB memory is available for program storage. So for large

applications we prefer microprocessor than microcontroller due to its high processing speed.

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4.4 PIN DIAGRAM OF 8051:-

Pins 1-8 (Port 1) - Each of these pins can be configured as an input or an output.

Pin 9 (Reset) - A logic one on this pin disables the microcontroller and clears the contents of most

registers. In other words, the positive voltage on this pin resets the microcontroller. By applying logic

zero to this pin, the program starts execution from the beginning.

Pins 10- 17 (Port 3) -Similar to port 1, each of these pins can serve as general input or output.

Besides, all of them have alternative functions:

Pin 10 (RXD) - Serial asynchronous communication input or Serial synchronous communication

output.

Pin 11(TXD) - Serial asynchronous communication output or Serial synchronous communication

clock output.

Pin 12 (INT 0) - Interrupt 0 input.

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Pin 13(INT 1) - Interrupt 1 input.

Pin 14(T0) - Counter 0 clock input.

Pin 15(T1) - Counter 1 clock input.

Pin 16(WR) -Write to external (additional) RAM.

Pin 17 (RD) -Read from external RAM.

Pin 18 and 19(X1, X2) - Internal oscillator input and output. A quartz crystal which specifies

operating frequency is usually connected to these pins. Instead of it, miniature ceramics resonators can

also be used for frequency stability. Later versions of microcontrollers operate at a frequency of 0 Hz

up to over 50 Hz.

Pin 20 (GND) - Ground.

Pin 21-28 (Port 2) - If there is no intention to use external memory then these port pins are configured

as general inputs/outputs. In case external memory is used, the higher address byte, i.e. addresses A8-

A15 will appear on this port. Even though memory with capacity of 64Kb is not used, which means

that not all eight port bits are used for its addressing, the rest of them are not available as

inputs/outputs.

Pin 29 (PSEN) - If external ROM is used for storing program then a logic zero (0) appears on it every

time the microcontroller reads a byte from memory.

Pin 30 (ALE) - Prior to reading from external memory, the microcontroller puts the lower address

byte (A0-A7) on P0 and activates the ALE output. After receiving signal from the ALE pin, the

external register memorizes the state of P0 and uses it as a memory chip address. Immediately after

that, the ALU pin is returned its previous logic state and P0 is now used as a Data Bus. As seen, port

data multiplexing is performed by means of only one additional (and cheap) integrated circuit. In other

words, this port is used for both data and address transmission.

Pin 31 (EA) - By applying logic zero to this pin, P2 and P3 are used for data and address transmission

with no regard to whether there is internal memory or not. It means that even there is a program

written to the microcontroller, it will not be executed. Instead, the program written to external ROM

will be executed. By applying logic one to the EA pin, the microcontroller will use both memories,

first internal then external (if exists).

Pin 32-39 (Port 0) - Similar to P2, if external memory is not used, these pins can be used as general

inputs/outputs. Otherwise, P0 is configured as address output (A0-A7) when the ALE pin is driven

high (1) or as data output (Data Bus) when the ALE pin is driven low (0).

Pin 40 (Vcc) - +5V power supply.

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4.5 MICROCONTROLLER 8051 ARCHITECTURE

It is 8-bit microcontroller, means MC 8051 can Read, Write and Process 8 bit data. This is mostly

used microcontroller in the robotics, home appliances likemp3 player, washing machines, electronic

iron and industries. Mostly used blocks in the architecture of 8051 are as follows:

Address bus-For a device (memory or I/O) to be recognized by the CPU, it must be assigned an

address. The address assigned to a given device must be unique. The CPU puts the address on the

address bus, and the decoding circuitry finds the device.

Data bus-The CPU either gets data from the device or sends data to it.

Control bus-Provides read or write signals to the device to indicate if the CPU is asking for

information or sending it information.

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4.6 Memory and Registers

The 8051 microcontroller has a total of 256 bytes of RAM in which 128 is visible or useraccessible

and extra 128 is for special function registers. The user accessible RAM is used for temporary data

storage. The user accessible RAM is from the address range 00 to 7Fh.From the user accessible RAM,

32 bytes of RAM is used for registers and rest for Stack operations. The 32 Bytes of RAM is divided

into four register Banks i.e. Bank0, Bank 1, Bank 2, Bank3. Each of these banks have 8 Registers i.e.

R0 to R7 each.

RAM locations from 0 to 7 are set aside for bank 0 of R0 – R7 where R0 is RAM location 0, Rl is

RAM location 1, and R2 is location 2, and so on, until memory location 7, which belongs to R7 of

bank 0. The second bank of registers R0 – R7 starts at RAM location 08 and goes to location 0FH.

The third bank of R0 – R7 starts at memory location 10H and goes to location 17H. Finally, RAM

locations 18H to 1FH are set aside for the fourth bank of R0 – R7.

Generally for normal operations, Register bank Bank0 is set by default. But we can switch to other

banks by using PSW Commands.

SFRs (Special Function Register) - These Registers are in extra 128 bytes of the memory. This part

of memory is not user accessible and these registers are used for special purposes. These

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registers range from 80h to FFh. There are a total of only 21 SFRs in this range and all other addresses

from 80h to FFh are invalid and there use can cause errors and not valuable results.

Some of the SFRs are TCON, SBUF, ACC, B, SCON, TMOD SP, P0, PSW, TL0, and TL1. These all

the registers have some specific function that has to be performed after they are programmed.

Byte Addressable SFR with byte address

SP – Stack printer – 81H

DPTR – Data pointer 2 bytes

DPL – Low byte – 82H

DPH – High byte – 83H

TMOD – Timer mode control – 89H

TH0 – Timer 0 Higher order bytes – 8CH

TL0 – Timer 0 Low order bytes – 8AH

TH1 – Timer 1 High bytes = 80H

TL1 – Timer 1 Low order byte = 86H

SBUF – Serial data buffer = 99H

PCON – Power control – 87H.

DPTR - Data Pointer in 8051

16 bit register; it is divided into two parts DPH and DPL.

DPH for Higher order 8 bits, DPL for lower order 8 bits.

DPTR, DPH, DPL these all are SFRs in 8051.

4.7 Timers and Counters:

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The 8051 has two timers T0 and T1, which may be configured and used individually. The 8052 has an

additional Timer T2.All these counters count up on negative going edges at their inputs. These can be

used as event counters (where they count the number of negative transitions on a pin connected to

some external source), or as Timers, where they count up once every twelfth clock cycle. A special

use of timers is for generating baud rates for the serial port. The usage of these timers is somewhat

different from common general purpose timer/counters such as the 8253 and 8254. This difference

stems partly from the fact that we cannot afford to have a large numbers of pins dedicated to the

functioning of these timer counters. Thus, just two multifunction pins are used as external inputs in

8051. Gating is accomplished by control bits in the special function registers, and using the external

interrupt pins as gate inputs. There are no output pins associated with the timers. The processor can

be interrupted by the timers and as a part of the interrupt service routine, the processor can performing

IO function through its ports. When used as baud rate generators, the output

goes directly to the serial port hardware within the microcomputer.

8051 timers always count up. Each counter has a 16 bit count register in the SFR area. The low and

high bytes can be accessed as separate bytes. When their

count rolls over from the maximum count to 0000, they set the corresponding

timer flag (TF1 or TF0) in TCON. The 8051 can be set up so that an interrupt occurs whenever TF1

or TF0 is set. when 8051 branches to the interrupt vector, it automatically clears the TF

flag.

Timer means which can give the delay of particular time between some events. For example on or

off the lights after every 2 sec. This delay can be provided through some assembly program but in

microcontroller two hardware pins are available for delay generation. These hardware pins can be

also used for counting

some external events. How much times a number is repeated in the given table is calculated by the

counter.

• In MC8051, two timer pins are available T0 and T1, by these timers we can

give the delay of particular time if we use these in timer mode.

• We can count external pulses at these pins if we use these pins in counter

mode.

• 16 bits timers are available. Means we can generate delay between 0000H

to FFFFH.

[21]

• Two special function registers are available.

• In the same way for T1.

• TMOD, TCON registers are used for controlling timer operation.

Basic registers of the timer

Timer 0 and Timer 1 are 16 bits wide

each 16-bit timer is accessed as two separate registers of low byte and high byte.

Timer 0 registers

low byte register is called TL0 (Timer 0 low byte) and the high byte register is referred to as TH0

(Timer 0 high byte)

can be accessed like any other register, such as A, B, R0, R1, R2, etc.

"MOV TL0, #4 FH" moves the value 4FH into TL0

"MOV R5, TH0" saves TH0 (high byte of Timer 0) in R5

Timer 1 registers

also 16 bits

split into two bytes TL1 (Timer 1 low byte) and TH1 (Timer 1 high byte)

accessible in the same way as the registers of Timer 0.

TMOD (timer mode) register

timers 0 and 1 use TMOD register to set operation modes (only learn Mode 1 and 2)

8-bit register

lower 4 bits are for Timer 0

upper 4 bits are for Timer 1

[22]

lower 2 bits are used to set the timer mode

(only learn Mode 1 and 2)

upper 2 bits to specify the operation

(only learn timer operation)

Clock source for timer

timer needs a clock pulse to tick

if C/T = 0, the crystal frequency attached to the 8051 is the source of the clock for the timer

frequency for the timer is always 1/12th the frequency of the crystal attached to the 8051

XTAL = 11.0592 MHz allows the 8051 system to communicate with the PC with no errors

In our case, the timer frequency is 1MHz since our crystal frequency is 12MHz

Using Windows calculator to find TH, TL

Windows scientific calculator can be use to find the TH, TL values

Lets say we would like to find the TH, TL values for a time delay that uses 35,000 clocks of 1.085ms

open scientific calculator and select decimal

enter 35,000

[23]

select hex - converts 35,000 to hex 88B8H

select +/- to give -35000 decimal (7748H)

the lowest two digits (48) of this hex value are for TL and the next two (77) are for TH

C/T bit in TMOD register

used as a timer, the 8051's crystal is used as the source of the frequency

used as a counter, pulse outside the 8051 increments the TH, TL registers

counter mode, TMOD and TH, TL registers are the same as for the timer

timer modes are the same as well

C/T bit in TMOD register

C/T bit in the TMOD register decides the source of the clock for the timer

C/T = 0, timer gets pulses from crystal

C/T = 1, the timer used as counter and gets pulses from outside the 8051

C/T = 1, the counter counts up as pulses are fed from pins 14 and 15

pins are called T0 (Timer 0 input) and T1 (Timer 1 input)

these two pins belong to port 3

Timer 0, when C/T = 1, pin P3.4 provides the clock pulse and the counter counts up for each clock

pulse coming from that pin

Timer 1, when C/T = 1 each clock pulse coming in from pin P3.5 makes the counter count up

TCON register

[24]

TR0 and TR1 flags turn on or off the timers

bits are part of a register called TCON (timer control)

upper four bits are used to store the TF and TR bits of both Timer 0 and Timer 1

lower four bits are set aside for controlling the interrupt bits

"SETB TRl" and "CLR TRl“

"SETB TCON. 6" and "CLR TCON. 6“

Timer Func tions

When used as timers, the 8051 timers count up every 12th clock cycle. This is

selected by clearing the corresponding C/T flags in the TMOD special function

register, placed at the address 89H.

Timer modes

[25]

Table 9–2 Equivalent Instructions for the Timer Control Register (TCON)

The timers may operate in one of four modes:

Mode 0 In this mode, the timers act as 13 bit counters. This mode is largely meant for providing

compatibility with an older microcontroller from Intel(8048). This mode is practically never used in

fresh designs. Except for the counter size, this mode is identical to mode 1.

Mode 1 In this mode, the timers are 16 bits in size. This is a commonly used mode. It is common

to configured the timer to cause an interrupt when it overflows. The interrupt routine then reloads the

timer.

Mode 2 This mode provides an 8 bit counter with auto-reload. It uses the high byte of the count

register to store the count value and the low byte as the actual counter. The counter is automatically

re-loaded from TH when it overflows. Thus, there is no software overhead for re-loading the

registers. This is convenient for generating baud rates etc. The timing resolution is much lower in

this mode (only 8 bits). Therefore crystal frequencies have to be carefully chosen to generate

accurate baud rates. Crystals of 11.059MHz are often used rather than 12 MHz for this reason.

Mode 3 In this mode Timers T0 and T1 behave quite divergently. T0 acts as two independent 8 bit

counters. Count register TL0 uses the resources (such as the RUN flag, overflows flag) in TCON,

TMOD etc. meant for T0. Similarly,TH0 uses the resources meant for T1. Thus, TR1 will enable

running the 8 bit counter made up of TH0. TF1 will be set whenever TH0 overflows.T1 now has no

control bits at all! It can only be used for services which require no control, no gating and no

interrupts. Thus, T1 can be used for Baud rate generation, while we still have two timers available

(both with 8 bit resolution).

Serial Port

• There are two pins available for serial communication TXD and RXD.

• Normally TXD is used for transmitting serial data which is in SBUF register,

RXD is used for receiving the serial data.

• SCON register is used for controlling the operation.

• There are four modes of serial communication which has been discussed in

next chapter.

OSSCILLATORS

[26]

It is used for providing the clock to MC8051 which decides the speed orbaud rate of MC.

We use crystal which frequency vary from 4MHz to 30 MHz, normally we

use 11.0592 MHz frequency.

INTERRUPTS

Interrupts are defined as requests because they can be refused (masked) if

they are not used, that is when an interrupt is acknowledged. A special set

of events or routines are followed to handle the interrupts. These special

routines are known as interrupt handler or interrupt service routines (ISR).

These are located at a special location in memory.

INT0 and INT1 are the pins for external interrupts.

[27]

ARCHUTECTURE OF 8051:-

ALU Arithmetic Logical Unit: This unit is used for the arithmetic calculations.

Accumulator: This register is used for arithmetic operations. This is also bit addressable and 8 bit

register.

B-Register: This register is used in only two instructions MUL AB and DIV AB. This is also

bit addressable and 8 bit register.

PC-Program Counter

• Points to the address of next instruction to be executed from ROM

• It is 16 bit register means the 8051 can access program address from

0000H to FFFFH. A total of 64KB of code. 16 bit register means.

[28]

STACKS IN 8051:-

[29]

5.PROGRAMMING AND INTERFACING:-5.1 INPUT DEVICES INTERFACING

5.1.1 SWITCH

Fig-2.1-Various Types Of Switches

Fig. 1 Switches are used to open/close a circuit

Fig. 2  S1 is a "single pole on/off" switch in the off position

Fig. 3 This is a "2 pole on/off" switch which completely isolates the lamp from the supply in the off

position. This may be important if it is a high voltage supply. The dotted line indicates that S1a and

S1b are part of the same switch "ganged" together and operate simultaneously.

Fig. 4 This is a "single pole changeover" switch. Either lamp 1 or lamp 2 is on.

Fig. 5this is a "2 pole changeover" switch. The unlit lamp is completely isolated from the supply.

Again S1a and S1b are part of the same switch

Fig. 6this is a "single pole 5 way" switch. It can select 1 of 5 circuits. You can have 2p 5w, 3p 4w

etc

Fig. 8 This is a "changeover" slide switch. When operated a-b opens and b-c closes

[30]

1 INTERFACING WITH AT89S52-

In 8051 PORT 1, PORT 2 & PORT 3 have internal 10k Pull-up resistors whereas this Pull-up resistor

is absent in PORT 0. Hence PORT 1, 2 & 3 can be directly used to interface a switch whereas we have

to use an external 10k pull-up resistor for PORT 0 to be used for switch interfacing or for any other

input. Figure 2.2 shows switch interfacing for PORT 1, 2 & 3. Figure 2.3 shows switch interfacing to

PORT 0. 

Fig 2.2 - Switch Interfacing For Port 1, 2 & 3

For any pin to be used as an INPUT PIN a HIGH (1) should be written to the pin if you don’t do this

the pin will always be read as LOW.In the above figure when the switch is not pressed the 10k resistor

provides the current needed for LOGIC 1 closure of switch provides LOGIC 0 to the controller

PIN.Let's write a small program where whenever a switch is pressed a LED is turned ON. Consider

that switch is connected to P2.0 & an LED connected to P2.1.

Program of switch interfacing-

Main()

{

P2_0==1;

SETB P2_1==0;

While(1)

{

If(P2_0==0)

{

P2_1==1;

}

Else

{

P2_1==0;

}

}

[31]

OUTPUT DEVICES INTERFACING

5.2.1 LED INTERFACING

C CODE FOR BLINKING LEDS CONNECTED ON PORT2:

#include<at89s8252.h>

void delay(unsigned int i);

void main(void)

{While(1){P2=0x00;Delay(0xffff);P2=0x00;Delay(0xff);}}void delay(unsigned int i){while(i!=0){i--;}}

Fig:-3.1-Hardware Interfacing Of Led With At89s52

[32]

3.1.2 C CODE FOR RUNNING LED CONNECTED ON PORT2:

#include<at89s8252.h>

void delay(unsigned int i);

void main (){P0=0x00;while (1){delay(0xffff);P2_0=1;delay(0xffff);P2_0=0;P2_1=1;delay(0xffff);P2_1=0;P2_2=1;delay(0xffff);P2_2=0;P2_3=1;delay(0xffff);P2_3=0;P2_4=1;delay(0xffff);P2_4=0;P2_5=1;delay(0xffff);P2_5=0;P2_6=1;delay(0xffff);P2_6=0;P2_7=1;delay(0xffff);P2_7=0;P2_0=1}}void delay(unsigned int i){while (i!=0){

i--;

}

}

5.2.2 LCD(JHD162A) INTERFACING:

[33]

On most displays, the pins are numbered on the LCD’s printed circuit board, but if not, it is quit easy

to locate pin1. Since the pin is connected to ground, it often has a thicker PCB track connected to it,

and it is generally connected to the metal work at some point.

Fig:-3.2-Jhd162a LCD(16x2)

Three command control inputs. When this line is low, data bytes transferred to the display are treated

as commands, and data bytes read from the display indicate its status. By setting the RS line high,

character data can be transferred to and from the module.

Pin 5 is (R/W) line. This line is pulled low in order to write commands or character data to the

module, or pulled high to read character data or status information from its registers.

Pin 6 is Enable (E) line. This input is used to initiate the actual transfer of commands or character data

between the module and the data lines. When writing to the display, data is transferred only on the

high to low transition of this signal. However, when reading from the display, data will become

available shortly after the low to high transition and remain available until the signal falls low again

C CODE FOR LCD DISPLAY//Program to study basics of LCD#include"AT89S8252.h"//macro directives of LCD#define LCD P1#define RS P3_3#define EN P3_4//prototyping various functions of LCDvoid delay(unsigned int d);void lcd_cmd(unsigned char c);void lcd_init(void);void cursor_position(unsigned char p);void display(unsigned char h);//program to display character 'A'void main(){

lcd_init();cursor_position(0);

[34]

display('A');}

//defining delay functionvoid delay(unsigned int d){

while(d!=0)d--;

}//subprogram to send various commands to LCDvoid lcd_cmd(unsigned char c){

delay(300);LCD=c;RS=0;EN=1;EN=0;

}//subprogram too initialize LCDvoid lcd_init(void){

lcd_cmd(0x01);lcd_cmd(0x38);lcd_cmd(0x0C);

}

//subprogram to set cursor positionvoid cursor_position(unsigned char p){

lcd_cmd(0x80+p);}

//subprogram to display data on LCDvoid display(unsigned char h){

delay(300);LCD=h;RS=1;EN=1;EN=0;

}

C CODE FOR STRING DISPLAY ON LCD:

void main()

[35]

{

while(1)

{

unsigned char name[]={"hello&"};

unsigned char group[]={"Group 3&"};

lcd_init();

cursor_position(0);

string_display(name);

cursor_position(40); //to display string on second row of LCD

string_display(group);

}

}

//function to display string

void string_display(unsigned char *s)

{

while(*s!='&')

{

display(*s);

delay(0xffff);

s++;

}

}

5.2.3 SEVEN SEGMENT DISPLAY

The 7 segment display is used as a numerical indicator on many types of test equipment.

[36]

Fig:-3.4-Basic Diagram Of A Seven Segment Display

It is an assembly of light emitting diodes which can be powered individually. They most commonly

emit red light. They are arranged and labeled as shown in the figure 3.4.

Powering all the segments will display the number 8. Powering a,b,c d and g will display the number

3. Numbers 0 to 9 can be displayed. The d.p represents a decimal point. The one shown is a common

anode display since all anodes are joined together and go to the positive supply. The cathodes are

connected individually to zero volts. Resistors must be placed in series with each diode to limit the

current through each diode to a safe value.

Early wrist watches used this type of display but they used so much current that the display was

normally switched off. To see the time you had to push a button. Common cathode displays where all

the cathodes are joined are also available. Liquid crystal displays do a similar job and consume much

less power. Alphanumeric displays are available which can show letters as well as numbers

C CODE TO INTERFACE SEVEN SEGMENT WITH AT89S52 AND DISPLAY NUMBERS 0

TO 99

#include"at89s8252.h"

void delay(unsigned int d);

void bcd(unsigned int x);

void main()

{

unsigned char i;

while(1)

{

for(i=0;i<100;i++)

{

bcd(i);

}

[37]

}

}

void delay(unsigned int d)

{

while(d!=0)

{

d--;

}

}

5.2.4 RELAY INTERFACING

The electromagnetic relay consists of a multi-turn coil, wound on an iron core, to form an

electromagnet.  When the coil is energised, by passing current through it, the core becomes

temporarily magnetised.

Fig:-3.5-Basic Relay Circuit

The magnetized core attracts the iron armature. The armature is pivoted which causes it to operate one

or more sets of contacts. When the coil is de-energized the armature and contacts are released. The

coil can be energized from a low power source such as a transistor while the contacts can switch high

powers such as the mains supply. The relay can also be situated remotely from the control source.

Relays can generate a very high voltage across the coil when switched off.

This can damage other components in the circuit. To prevent this a diode is connected across the coil.

The cathode of the diode is connected to the most positive end of the coil.

[38]

Fig:-3.6-Basic Relay Leads

The spring sets (contacts) can be a mixture of normally open , normally closed and  change over.The

actual contact points on the springsets are available for high current and low current operation. Relays

are devices which allow low power circuits to switch a relatively high Current/Voltage ON/OFF. For a

relay to operate a suitable pull-in & holding current should be passed through its coil. Generally relay

coils are designed to operate from a particular voltage often its 5V or 12V.

The function of relay driver circuit is to provide the necessary current (typically 25 to 70ma) to

energize the relay coil.

Fig:-3.7- Basic Relay Interfacing With At89s8252

Figure 3.7 shows the basic relay driver circuit. As you can see an NPN transistor BC547 is being used

to control the relay. The transistor is driven into saturation (turned ON)  when a LOGIC 1 is written on

the PORT PIN thus turning ON the relay. The relay is turned OFF by writing LOGIC 0 on the port

pin.

[39]

5.2.5 MOTORS INTERFACING

4.1 L293D DUAL H-BRIDGE MOTOR DRIVER

L293D is a dual H-Bridge motor driver, So with one IC we can interface two DC motors which can be

controlled in both clockwise and counter clockwise direction and if you have motor with fix direction

of motion the you can make use of all the four I/Os to connect up to four DC motors. L293D has

output current of 600mA and peak output current of 1.2A per channel. Moreover for protection of

circuit from back EMF output diodes are included within the IC. The output supply (VCC2) has a

wide range from 4.5V to 36V, which has made L293D a best choice for DC motor driver.

.

Fig 4.1- Interfacing A Dc Motor Using L293d

As you can see in the circuit, three pins are needed for interfacing a DC motor (A, B, Enable). If you

want the o/p to be enabled completely then you can connect Enable to VCC and only 2 pins needed

from controller to make the motor work.

As per the truth mentioned in the image above its fairly simple to program the microcontroller. Its also

clear from the truth table of BJT circuit and L293D the programming will be same for both of them,

just keeping in mind the allowed combinations of A and B. We will discuss about programming in C

as well as assembly for running motor with the help of a microcontroller

.

C CODE FOR INTERFACING STEPPER MOTOR

[40]

#include<8051.h>

#define s4 P0_0

#define s2 P0_1

#define s3 P0_2

#define s1 P0_3

void delay(unsigned int a);

void full_stepping(void);

void main()

{

P0=0x00;

while(1)

{

full_stepping();

}

}

void full_stepping(void)

{

s1=1;s2=1;s3=0;s4=0;

delay(1500);

s1=0;s2=1;s3=1;s4=0;

delay(1500);

s1=0;s2=0;s3=1;s4=1;

delay(1500);

s1=1;s2=0;s3=0;s4=1;

delay(1500);

}

void delay(unsigned int a)

{

while(a!=0)

{

a--;

}

}

5.2.6 INTERFACING CONVERTERS (ADC)

[41]

5.1 ADC-0804 INTERFACING WITH AT89S52:

The ADC0804 family is CMOS 8-Bit, successive-approximation A/D converters which use a modified

potentiometer ladder and are designed to operate with the 8080A control bus via three-state outputs.

These converters appear to the processor as memory locations or I/O ports, and hence no interfacing

logic is required. The differential analog voltage input has good common mode- rejection and permits

offsetting the analog zero-input voltage value. In addition, the voltage reference input can be adjusted

to allow encoding any smaller analog voltage span to the full 8 bits of resolution.

5.1.1 Features

• 80C48 and 80C80/85 Bus Compatible - No Interfacing Logic Required

• Conversion Time < 100us

• Easy Interface to Most Microprocessors

• Differential Analog Voltage Inputs

• TTL Compatible Inputs and Outputs

• On-Chip Clock Generator

• 0V to 5V Analog Voltage Input Range (Single + 5V Supply)

• No Zero-Adjust Required

5.1.2 ADC-0804 PIN DIAGRAM

Fig.-5.1-adc-0804 pin diagram

Hardware interfacing of ADC-0804

[42]

R 21 0 K

C 61 0 u F 1 6 V

V C C

C 1 31 0 4

EOC

SOC

V C C

C 1 41 u f / 1 6 v

R 62 2 0 E

U 4A D C 0 8 0 4

+ I N6

-I N7

AG

ND

8V R E F / 2

9

GN

D10

D B 71 1 D B 61 2 D B 51 3 D B 41 4 D B 31 5 D B 21 6 D B 11 7 D B 01 8

C L K R1 9

VC

C/V

RE

F20

C L K I N4

I N TR5

C S1

R D2

W R3

V C C

R 51 0 K

R 1 71 0 K

C 71 5 0 p F

U 2 1TL 4 3 1

23

1

C 81 u f / 1 6 v

C 9C A P

R SE N

L C D

C O N 1 6 _ 0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

V C CR S E N R 5 5

5 6 E

Temprature monitoring system

U 2 2 L M 3 5 / S O

G N D3

V C C1

2

O U TP U T

R 5 31 k

V C C

U 2

A T8 9 S 8 2 5 2

R S T9

XTA L 21 8 XTA L 11 9

GN

D20

P S E N2 9 A L E / P R O G3 0

EA

/VP

P31

VC

C40

P 1 . 0 / T21

P 1 . 1 / T2 -E X2

P 1 . 23

P 1 . 34

P 1 . 4 / S S5

P 1 . 5 / M O S I6

P 1 . 6 / M I S O7

P 1 . 7 / S C K8

P 2 . 0 / A 82 1

P 2 . 1 / A 92 2

P 2 . 2 / A 1 02 3

P 2 . 3 / A 1 12 4

P 2 . 4 / A 1 22 5

P 2 . 5 / A 1 32 6

P 2 . 6 / A 1 42 7

P 2 . 7 / A 1 52 8

P 3 . 0 / R XD1 0

P 3 . 1 / TXD1 1

P 3 . 2 / I N T0 1 2

P 3 . 3 / I N T11 3

P 3 . 4 / T01 4

P 3 . 5 / T11 5

P 3 . 6 / W R1 6

P 3 . 7 / R D1 7

P 0 . 0 / A D 03 9 P 0 . 1 / A D 13 8 P 0 . 2 / A D 23 7 P 0 . 3 / A D 33 6 P 0 . 4 / A D 43 5 P 0 . 5 / A D 53 4 P 0 . 6 / A D 63 3 P 0 . 7 / A D 73 2

C 43 3 p F

C 53 3 p F

Y 2

C R Y S TA L

12

3

4

V C CV C C

Fig.-5.2- hardware interfacing of adc-0804 for temperature monitoring

When interfacing is being done then gets lowered then only it allows the controller to read the

data, otherwise controller can not read the data.

is always grounded.

is software controlled.

C- CODE FOR TEMPERATURE MONITORING SYSTEM

#include <at89s8252.h>

#define SOC P3_2

#define EOC P3_5

unsigned char read_adc(void);

void disp_dec(unsigned int digit);

code unsigned char table[16]={'0','1','2','3','4','5','6','7','8','9'};

void main(void)

{

unsigned char e;

P2=0xff;

Init_lcd();

while(1)

{ cursor_position(0x00);

[43]

e=read_adc(); disp_dec(e); }} unsigned char read_adc(void) { unsigned char n; SOC=0; SOC=1; while(EOC==1) {

n=P2; }

return n;

}

void disp_dec(unsigned int digit)

{

unsigned int temp;

if(digit<100)

{

temp=digit/10;

display(table[temp]);

temp=digit-temp*10;

display(table[temp]);

}

if(digit>99 && digit<1000)

{

temp=digit/100;

display(table[temp]);

digit=digit-(temp*100);

temp=digit/10;

display(table[temp]);

digit=digit-(temp*10);

temp=digit;

display(table[temp]); }

5.2.7 COMMUNICATION

[44]

6.1 Serial communication between At89s52 and PC

One of the 8051s many powerful features is its integrated UART, otherwise known as a serial port. The

fact that the 8051 has an integrated serial port means that you may very easily read and write values to

the serial port. If it were not for the integrated serial port, writing a byte to a serial line would be a

rather tedious process requring turning on and off one of the I/O lines in rapid succession to properly

"clock out" each individual bit, including start bits, stop bits, and parity bits.

6.1.1 SETTING THE SERIAL PORT MODE -

The first thing we must do when using the 8051s integrated serial port is, obviously, configure it. This

lets us tell the 8051 how many data bits we want, the baud rate we will be using, and how the baud

rate will be determined.

First, lets present the "Serial Control" (SCON) SFR and define what each bit of the SFR represents:

Table 6.1-Scon Register

[45]

Bit NameBit

AddressExplanation of Function

7 SM0 9Fh Serial port mode bit 0

6 SM1 9Eh Serial port mode bit 1.

5 SM2 9Dh Mutliprocessor Communications Enable (explained later)

4 REN 9ChReceiver Enable. This bit must be set in order to receive

characters.

3 TB8 9Bh Transmit bit 8. The 9th bit to transmit in mode 2 and 3.

2 RB8 9Ah Receive bit 8. The 9th bit received in mode 2 and 3.

1 TI 99h Transmit Flag. Set when a byte has been completely transmitted.

0 RI 98h Receive Flag. Set when a byte has been completely received.

SERIAL TRANSMISSION INTERFACING

SPT RXD

SPT TXD

U 5

A T8 9 S 8 2 5 2

R S T9

XTA L 21 8 XTA L 11 9

GN

D20

P S E N2 9

A L E / P R O G3 0

EA

/VP

P31

VC

C40

P 1 . 0 / T21

P 1 . 1 / T2 -E X2

P 1 . 23

P 1 . 34

P 1 . 4 / S S5

P 1 . 5 / M O S I6

P 1 . 6 / M I S O7

P 1 . 7 / S C K8

P 2 . 0 / A 82 1

P 2 . 1 / A 92 2

P 2 . 2 / A 1 02 3

P 2 . 3 / A 1 12 4

P 2 . 4 / A 1 22 5

P 2 . 5 / A 1 32 6

P 2 . 6 / A 1 42 7

P 2 . 7 / A 1 52 8

P 3 . 0 / R XD1 0P 3 . 1 / TXD1 1

P 3 . 2 / I N T01 2

P 3 . 3 / I N T11 3

P 3 . 4 / T01 4

P 3 . 5 / T11 5

P 3 . 6 / W R1 6P 3 . 7 / R D1 7

P 0 . 0 / A D 03 9

P 0 . 1 / A D 13 8

P 0 . 2 / A D 23 7

P 0 . 3 / A D 33 6

P 0 . 4 / A D 43 5

P 0 . 5 / A D 53 4

P 0 . 6 / A D 63 3

P 0 . 7 / A D 73 2

C 1 63 3 p F

C 1 73 3 p F

Y 4

C R Y S TA L

123

4

V C CV C C

R 41 0 K

C 1 81 0 u F 1 6 V

V C C

C 1 91 0 4

C 2 01 0 U F / 1 6 V

C 2 11 0 U F / 1 6 V

V C C

V C C

C 2 21 0 U F / 1 6 V

C 2 31 0 4

C 2 4 1 0 U F / 1 6 V

U 6

M A X2 3 2

C 1 +1

C 1 -3

C 2 +4

C 2 -5

VC

C16

GN

D15

V +2

V -6

R 1 O U T1 2

R 2 O U T9

T1 I N1 1

T2 I N1 0

R 1 I N1 3

R 2 I N8

T1 O U T1 4

T2 O U T7

J 7

S E R I A L P O R T O F P C

123

Fig.7.1-Max232 Interfacing With At89s52 For Serial Transmission

C- CODE FOR SERIAL TRANSMISSION(FROM MICROCONTROLLER TO PC)

#include<at89s8252.h>

void Init_SPT(void);

void transmit_serial(unsigned char a);

void delay(unsigned int i);

void main(void)

{

Init_SPT();

while(1)

{

delay(0XFFFF);

transmit_serial('N');

delay(0XFFFF);

transmit_serial('E');

delay(0XFFFF);

transmit_serial('T');

delay(0XFFFF);

transmit_serial('M');

delay(0XFFFF);

transmit_serial('A');

delay(0XFFFF);

[46]

transmit_serial('X');

delay(0XFFFF);

}

}

void Init_SPT(void)

{

TMOD=0x20;

TH1=0xfd;

TR1=1;

SCON=0x40;

}

void transmit_serial(unsigned char a)

{

SBUF=a;

delay(500);

TI=0;

}

void delay(unsigned int i)

{

while(i!=0)

{

i--;

}

}

ELECTRONIC VOTING MACHINE USING 8051

MICROCONTROLLER

[47]

List of Contents

Abstract 50

1. Background 51

2. Microcontroller 56

2.1 Introduction 56

2.2 History 56

2.3 Definition of a Microcontroller 58

2.4 Microcontrollers vs Microprocessors 58

2.5 Memory Unit 58

2.6 Central Processing Unit 59

2.7 Bus 59

2.8 Input Output Unit 59

2.9 Serial Communication 60

2.10 Timer Unit 60

2.11 Watch Dog 61

2.12 Analog to Digital Converter 61

3. Introduction to 16X2 LCD Display 63

3.1 Pin description 63

3.2 DDRAM - Display Data RAM 64

3.3 BF - Busy Flag 64

3.4 Instruction Register (IR) and Data Register (DR) 64

3.5 Commands and Instruction set 64

3.6 Sending Commands to LCD 64

4. Project Description 65

4.1 Block diagram 65

4.2 General working 65

4.3 C language code 68

5. Project Methodology 72

5.1 Components 72

5.2 Software used 72

5.3 Equipments used 72

[48]

6. Result and Conclusion 73

7. Applications 73

8. Future Scope 73

9. References and Bibliography 74

ABSTRACT

India is world’s largest democracy. It is perceived to be charismatic one as it

accommodates cultural, regional, economical, social disparities and still is able to stand on its own.

Fundamental right to vote or simply voting in elections forms the basis of Indian democracy.

[49]

In India all earlier elections be it state elections or centre elections a voter used to cast his/her

vote to his/her favorite candidate by putting the stamp against his/her name and then folding the

ballot paper as per a prescribed method before putting it in the Ballot box. This is a long, time-

consuming process and very much prone to errors. This situation continued till election scene was

completely changed by electronic voting machine. No more ballot paper, ballot boxes, stamping,

etc. all this condensed into a simple box called ballot unit of the electronic voting machine.

EVM is capable of saving considerable printing stationery and transport of large volumes of electoral

material. It is easy to transport, store, and maintain. It completely rules out the chance of invalid

votes. Its use results in reduction of polling time, resulting in fewer problems in electoral

preparations, law and order, candidates expenditure, etc. and easy and accurate counting without

any mischief at the counting centre. It is also eco friendly. Our EVM consists of one microcontroller

AT89S52. The unit consists of one LCD, 6 push buttons, couple of switches, an LED and a buzzer,

etc. The port 0 of microcontroller is used for interfacing the led, port 2 is used for control

switches, port 3 is used for Interfacing push buttons for voting.

BACKGROUND

Democracy and Voting

Democracy has come to be accepted as the most preferred form of political system all over the

world. However, the success of a democratic structure is to be judged by the successes that can be

[50]

solely attributed to this system. There are various challenges before democracy. These are

foundational challenges, challenge of expansion and deepening of democracy. All of these are

dependent on how the democracy is perceived by people who form the government, participate in

formation of government and are benefited by it. As we all know that India is world’s largest

democracy. It is perceived to be charismatic one as it accommodates cultural, regional, econo mical,

social disparities and still is able

to stand on its own. India follows a federal form of government. It means that governance power is

not residing with one authority, but is distributed at various levels. In India power is distributed

between states and central authority.

What forms the basis of such vast and complex system of governance?

One needs not to be an Einstein to guess the answer. It is fundamental right to vote or

simply voting in elections.

Indian constitution provide every adult above the age of 18 years irrespective of his/her

religion, region, caste, creed, color, economic status, education and sex the essential right

to vote and elect her/his candidate to represent her/him.

Hence voting can be termed as backbone of not just democracy in India but all around the

world. Voting can be done in various ways. In early Roman Empire voting used to be

done by raising hands in favor or against. In board rooms voting is done in similar way,

some write their vote down, some choose to speak, some choose to cast vote using latest

technology.

Voting Techniques

In India all earlier elections be it state elections or centre elections a voter used to cast

his/her vote to his/her favorite candidate by putting the stamp against his/her name and

then folding the ballot paper as per a prescribed method before putting it in the Ballot

box. This is a long, time-consuming process and very much prone to errors.

This method wanted voters to be skilled voters to know how to put a stamp, and

methodical folding of ballot paper. Millions of paper would be printed and heavy ballot

boxes would be loaded and unloaded to and from ballot office to polling station. All this

continued till election scene was completely changed by electronic voting machine. No

more ballot paper, ballot boxes, stamping, etc. all this condensed into a simple box called

ballot unit of the electronic voting machine.

The marking system of voting was introduced in 1962 to make it possible for a

substantial number of illiterate voters to indicate easily their preferences in choosing their

representatives. Over the years, there was a pronounced increase in the volume of work:

crores of ballot papers had to be printed and lakhs of ballot boxes had to be prepared,

transported, and kept in storage; and a great amount of time was taken up by the conduct

[51]

of elections. To overcome these difficulties, the Election Commission of India (ECI)

thought of electronic gadgets. The Electronics Corporation of India Ltd. (ECIL),

Hyderabad, and Bharat Electronics Ltd. (BEL), Bangalore, developed the electronic

voting machine in 1981.

The Electronic Voting Machine

The complete EVM consists mainly of two units - (a) Control Unit and (b) Balloting Unit

with cable for connecting it with Control unit. A Balloting Unit caters upto 16 candidates.

Four Balloting Units linked together catering in all to 64 candidates can be used with one

control unit. The control unit is kept with the Presiding Officer and the Balloting Unit is

used by the voter for polling.

The Balloting Unit of EVM is a small Box-like device, on top of which each candidate

and his/her election symbol is listed like a big ballot paper. Against each candidate's

name, a red LED and a blue button is provided. The voter polls his vote by pressing the

blue button against the name of his desired candidate.

How the Vote is cast with this EVM?

The entire process is very easy to understand:

• Like in earlier system, your name is called and you are asked to sign or put your

thumb impression in a register.

• After your identification is done by Election Officer, an ink mark is put on your

finger, same as earlier.

• Then the Election Officer gives you a slip that bears the Voter register number

where you signed or put your thumb impression.

• You hand over this slip to the presiding officer who confirms the serial number

and permits you to vote by pressing the button of the Control Unit of EVM.

• You are not given any ballot thereafter, and are sent to the EV Machine placed

behind a card board in a corner. The machine is placed in such a way that your

polled vote will be a secret. On the Balloting Unit of EVM, you press the button placed in front

of your favorite candidate and release.

Compare and Contrast: Paper Voting and EVM

We have so far discussed three different voting systems. These systems are being used or

considered obsolete because of certain positive and negative points. These are

summarized as follows:

[52]

Device type

Ballot paper : Papers and boxes

EVM : Embedded system with Assembly code

Visual Output

Ballot paper : Stamp on paper

EVM : Single LED against each candidate's name

Operating System/ Software

Ballot paper : No operating system

EVM : None, the Assembly code to register number of votes is all it has

Hence it is simple automation of voting, no complexities.

Records/ Audits

Ballot paper : Manual counting to be done by officials, lengthy, time consuming

Process. Inaccurate due to human errors.

EVM : The Voting unit doesn't store anything, the control unit records the number of votes cast for

each candidate against his serial number.

No record to link person-to-vote.

Control and Operation

Ballot paper: Manual operation

EVM : Automatic operation. The control Unit accumulates the votes, it is a device with flash

storage and seven segment LED displays. The ballot unit has a button to issue a ballot for a voter.

Security Issues

Ballot paper : No security provided by the system, neither during polling nor during voting.

EVM : During polling, a facility is provided to seal the machine in case of booth

capturing. No further voting can be done afterwards.

Ballot Issue

Ballot paper : Ballot paper is issued by Electoral officer on which voter could cast his vote.

EVM : Ballot is issued by Electoral officer by pressing a button on the control Unit.

It allows the voter to press any button on the ballot unit to cast his vote.

Storage of Votes

Ballot paper : In ballot boxes assigned for the purpose of storing votes, highly insecure method

of storage.

EVM : In Internal Non removable memory of the Control Units. No transfer over

network. Security increases with this feature. Moreover these results cant be accessed by authorized

[53]

personnel

only at commissioned offices..

Cost of the System

Ballot paper : High cost of paper printing in millions and low speed of the whole process.

EVM : About 12000 INR (300$) for one EVM.

Power Supply

Ballot paper : No power supply required.

EVM : 6V alkaline batteries or electricity.

Capacity

Ballot paper : As much a ballot box can hold.

EVM : 3840 Votes .

Existing System

But this electronic voting machine has its disadvantages too. These areas of deficiency

are not much of a concern to a layman, but for an intelligent voter this must be eliminated

for a secure election. The few technical disadvantages are given as:

• Microprocessor based design, which requires a no. of supporting components like

memory, peripheral interface, etc.

• No security against illegal viewing of results, as presiding officer can view the

results without any difficulty.

• Less user friendly due to two seven segment displays

• Existing system costs high.

Proposed System

All these faults motivated us to make this new enhanced EVM. The faults which are

eliminated are summarized as follows:

• Microcontroller replaced microprocessor, which made the EVM closer to real

time operation making it faster, more reliable and unique.

• More user friendly and interactive LCD display

• Proposed system costs less.

• As soon as the button is pressed, the LED indicator lights off and a whistle sound

comes from the machine. This signifies that your vote has been casted rightly.

Now you can come out.

• In case of LED not not being turned off, press the button firmly again. If finding it

difficult, consult the Presiding Officer.

[54]

• Your vote is complete safe and secret and there is no room for error as well. You

can rest assured that your vote is not going to be invalid in any case.

• The Voting Machine is attached to the 'Control Unit'. When the user presses the

button, his vote is registered in the control unit and the number of votes for the

respective candidates is calculated automatically.

Booth Capture

A remarkable advantage is that rigging is not possible with the EVMs. In the ballot paper

system, the intruders can mark hundreds of ballots and put them into the ballot box in a

matter of a few minutes. This is not possible in voting machines as the machine is

designed to cast only one vote and for the next vote to be casted the presiding officer

should make it ready by pressing the related button. Thus the presiding officer can have a

complete control of voting and avoid any kind of malpractices

The EVMs have following advantages:

• the saving of considerable printing stationery and transport of large volumes of

electoral material,

• easy transportation, storage, and maintenance,

• no invalid votes,

• reduction in polling time, resulting in fewer problems in electoral preparations,

law and order, candidates' expenditure, etc. and

• easy and accurate counting without any mischief at the counting centre

• eco friendly.

[55]

2. MICROCONTROLLERS

2.1 Introduction

Circumstances that we find ourselves in today in the field of microcontrollers had their

beginnings in the development of technology of integrated circuits. This development has

made it possible to store hundreds of thousands of transistors into one chip. That was a

prerequisite for production of microprocessors, and the first computers were made by

adding external peripherals such as memory, input-output lines, timers and other. Further

increasing of the volume of the package resulted in creation of integrated circuits. These

integrated circuits contained both processor and peripherals. That is how the first chip

containing a microcomputer, or what would later be known as a microcontroller came

about.

2.2 History

It was year 1969, and a team of Japanese engineers from the BUSICOM Company

arrived to United States with a request that a few integrated circuits for calculators be

made using their projects. The proposition was set to INTEL, and Marcian Hoff was

responsible for the project. Since he was the one who has had experience in working with

a computer (PC) PDP8, it occurred to him to suggest a fundamentally different solution

instead of the suggested construction. This solution presumed that the function of the

integrated circuit is determined by a program stored in it. That meant that configuration

would be simpler, but that it would require far more memory than the project that was

proposed by Japanese engineers would require. After a while, though Japanese engineers

tried finding an easier solution, Marcian's idea won, and the first microprocessor was

born. In transforming an idea into a ready made product, Frederico Faggin was a major

help to INTEL. He transferred to INTEL, and in only 9 months had succeeded in making

a product from its first conception. INTEL obtained the rights to sell this integral block in

1971. First, they bought the license from the BUSICOM Company who had no idea what

treasure they had. During that year, there appeared on the market a microprocessor called

4004. That was the first 4-bit microprocessor with the speed of 6 000 operations per second.

Not long after that, American company CTC requested from INTEL and Texas

Instruments to make an 8-bit microprocessor for use in terminals. Even though CTC gave

up this idea in the end, Intel and Texas Instruments kept working on the microprocessor

and in April of 1972, first 8-bit microprocessor appeared on the market under a name

8008.

[56]

2.3 Definition of a Microcontroller

Microcontroller, as the name suggests, are small controllers. They are like single chip

computers that are often embedded into other systems to function as

processing/controlling unit. For example, the remote control you are using probably has

microcontrollers inside that do decoding and other controlling functions. They are also

used in automobiles, washing machines, microwave ovens, toys ... etc, where automation

is needed.

The key features of microcontrollers include:

• High Integration of Functionality

• Microcontrollers sometimes are called single-chip computers because they have

on-chip memory and I/O circuitry and other circuitries that enable them to

function as small standalone computers without other supporting circuitry.

• Field Programmability, Flexibility

• Microcontrollers often use EEPROM or EPROM as their storage device to allow

field programmability so they are flexible to use. Once the program is tested to be

correct then large quantities of microcontrollers can be programmed to be used in

embedded systems.

• Easy to Use

[57]

2.4 Microcontrollers versus Microprocessors

Microcontroller differs from a microprocessor in many ways. First and the most

important is its functionality. In order for a microprocessor to be used, other components

such as memory, or components for receiving and sending data must be added to it. In

short that means that microprocessor is the very heart of the computer. On the other hand,

microcontroller is designed to be all of that in one. No other external components are

needed for its application because all necessary peripherals are already built into it. Thus,

we save the time and space needed to construct devices.

2.5 Memory unit

Memory is part of the microcontroller whose function is to store data.

The easiest way to explain it is to describe it as one big closet with lots of drawers. If we

suppose that we marked the drawers in such a way that they cannot be confused, any of

their contents will then be easily accessible. It is enough to know the designation of the

drawer and so its contents will be known to us for sure.

Typically, the amount of ROM type memory will vary between around 512 bytes and

4096 bytes, although some 16 bit microcontrollers such as the Hitachi H8/3048 can have

as much as 128 Kbytes of ROM type memory. ROM type memory, as has already been mentioned,

is used to store the program code. ROM memory can be ROM (as in One Time Programmable

memory), EPROM, or EEPROM. The amount of RAM memory is usually somewhat smaller,

typically ranging between 25 bytes to 4 Kbytes. RAM is used for data storage and stack

management tasks. It is also used for register stacks (as in the microchip PIC range of

microcontrollers). [58]

2.6 Central Processing Unit

Let add 3 more memory locations to a specific block that will have a built in capability to

multiply, divide, subtract, and move its contents from one memory location onto another.

The part we just added in is called "central processing unit" (CPU). Its memory locations

are called registers.

2.7 Bus

That "way" is called "bus". Physically, it represents a group of 8, 16, or more wires.

There are two types of buses: address and data bus. The first one consists of as many

lines as the amount of memory we wish to address and the other one is as wide as data, in

our case 8 bits or the connection line. First one serves to transmit address from CPU

memory, and the second to connect all blocks inside the microcontroller.

Figure2.4: Showing connection between memory and central unit using buses

2.8 Input-output unit

Those locations we've just added are called "ports". There are several types of ports:

input, output or bidirectional ports. When working with ports, first of all it is necessary to

choose which port we need to work with, and then to send data to, or take it from the

port.

2.9 Serial communication

[59]

Beside stated above we've added to the already existing unit the possibility of

communication with an outside world. However, this way of communicating has its

drawbacks. One of the basic drawbacks is the number of lines which need to be used in

order to transfer data. What if it is being transferred to a distance of several kilometers?

The number of lines times’ number of kilometers doesn't promise the economy of the

project. It leaves us having to reduce the number of lines in such a way that we don't

lessen its functionality. Suppose we are working with three lines only, and that one line is

used for sending data, other for receiving, and the third one is used as a reference line for

both the input and the output side. In order for this to work, we need to set the rules of

exchange of data. These rules are called protocol. Protocol is therefore defined in

advance so there wouldn't be any misunderstanding between the sides that are

communicating with each other. For example, if one man is speaking in French, and the

other in English, it is highly unlikely that they will quickly and effectively understand

each other. Let's suppose we have the following protocol. The logical unit "1" is set up on

the transmitting line until transfer begins.

Figure2.6: Serial unit sending data through three lines only

2.10 Timer unit

Since we have the serial communication explained, we can receive, send and process

data. However, in order to utilize it in industry we need a few additionally blocks. One of those

is the timer block which is significant to us because it can give us information about time,

duration, protocol etc. The basic unit of the timer is a free-run counter which is in fact a

register whose numeric value increments by one in even intervals, so that by taking its

value during periods T1 and T2 and on the basis of their difference we can determine

how much time has elapsed. This is a very important part of the microcontroller whose

understanding requires most of ourtime.

2.12 Analog to Digital Converter

[60]

As the peripheral signals usually are substantially different from the ones that

microcontroller can understand (zero and one), they have to be converted into a pattern

which can be comprehended by a microcontroller. This task is performed by a block for

analog to digital conversion or by an ADC. This block is responsible for converting an

information about some analog value to a binary number and for follow it through to a

CPU block so that CPU block can further process it.

Figure2.9: Block for converting an analog input to digital output

Finally, the microcontroller is now completed, and all we need to do now is to assemble it

into an electronic component where it will access inner blocks through the outside pins.

The picture below shows what a microcontroller looks like inside.

Figure2.10: Physical configuration of the interior of a microcontroller

Thin lines which lead from the center towards the sides of the microcontroller represent

wires connecting inner blocks with the pins on the housing of the microcontroller so

called bonding lines. Chart on the following page represents the center section of a

microcontroller.

[61]

Figure2.11: Microcontroller outline with basic elements and internal connections

2.13 AT89S52 microcontroller:

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K

bytes of in-system programmable Flash memory. The device is manufactured using

Atmel’s high-density nonvolatile memory technology and is compatible with the indus-

try-standard 80C51 instruction set and pinout. The on-chip Flash allows the program

memory to be reprogrammed in-system or by a conventional nonvolatile memory pro-

grammer. By combining a versatile 8-bit CPU with in-system programmable Flash on a

monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a

highly-flexible and cost-effective solution to many embedded control applications.

[62]

3. INTRODUCTION TO 16X2 LCD DISPLAY

LCD stands for Liquid Crystal Display. The most commonly used LCDs found in the

market today are 1 Line, 2 Line or 4 Line LCDs which have only 1 controller and support

at most of 80 characters.

3.1 Pin Description

Most LCDs with two controllers has 16 Pins. Pin description is shown in the table

below.

Pin No. Name Description

Pin no. 1 D7 Data bus line 7 (MSB)

Pin no. 2 D6 Data bus line 6

Pin no. 3 D5 Data bus line 5

Pin no. 4 D4 Data bus line 4

Pin no. 5 D3 Data bus line 3

Pin no. 6 D2 Data bus line 2

Pin no. 7 D1 Data bus line 1

Pin no. 8 D0 Data bus line 0 (LSB)

Pin no. 9 EN1 Enable signal for row 0 and 1 (1stcontroller)

Pin no. 12 VEE Contrast adjust

Pin no. 13 VSS Power supply (GND)

Pin no. 14 VCC Power supply (+5V)

Pin no. 15 EN2 Enable signal for row 2 and 3 (2ndcontroller)

Pin no. 16 NC Not Connected

Table No.3.1: Pin description of the LCD

[63]

3.2 DDRAM - Display Data RAM

Display data RAM (DDRAM) stores display data represented in 8-bit character codes. Its

extended capacity is 80 X 8 bits, or 80 characters. The area in display data RAM

(DDRAM) that is not used for display can be used as general data RAM. So whatever

you send on the DDRAM is actually displayed on the LCD.

3.3 BF - Busy Flag

Busy Flag is a status indicator flag for LCD. When we send a command or data to the

LCD for processing, this flag is set (i.e. BF =1) and as soon as the instruction is executed

successfully this flag is cleared (BF = 0). This is helpful in producing and exact amount

of delay. For the LCD processing. To read Busy Flag, the condition RS = 0 and R/W = 1

must be met and The MSB of the LCD data bus (D7) act as busy flag. When BF = 1

means LCD is busy and will not accept next command or data and BF = 0 means LCD is

ready for the next command or data to process.

3.4 Instruction Register (IR) and Data Register (DR)

There are two 8-bit registers controller Instruction and Data register. Instruction register

corresponds to the register where you send commands to LCD e.g. LCD shift command,

LCD clear, LCD address etc. and Data register is used for storing data which is to be

displayed on LCD. When send the enable signal of the LCD is asserted, the data on the

pins is latched in to the data register and data is then moved automatically to the

DDRAM and hence is displayed on the LCD.

3.5 Commands and Instruction set

Only the instruction register (IR) and the data register (DR) of the LCD can be controlled

by the MCU. Before starting the internal operation of the LCD, control information is

temporarily stored into these registers to allow interfacing with various MCUs, which

operate at different speeds, or various peripheral control devices. The internal operation

of the LCD is determined by signals sent from the MCU.

3.6 Sending Commands to LCD

To send commands we simply need to select the command register. Everything is same

as we have done in the initialization routine. But we will summarize the common steps

and put them in a single subroutine.

Following are the steps:

Move data to LCD port

Select command register

select write operation

[64]

send enable signal

PROJECT DESCRIPTION:-

BLOCK DIAGRAM

GENERAL WORKING:-1. Initially when the switch is closed, allows the evm to take the vote. the vote is taken only when push button is pressed and led D1 is switched ON.

[65]

2. A push button is assigned to each party. When the push button of the desired party is

pressed, the led is switched off which indicates that the vote is cast and the buzzer gives a

beep.

[66]

Again the push button is pressed so that the evm is ready to take the next vote which

isindicated through the led D1.The same process is repeated until all the voters cast theirvotes.

3. To view the results of each respective party, the switch must be opened

4. To know the result of the party, the push button of the respective party must be pressed so that the

number of votes cast for the party is displayed on the lcd screen.

[67]

This process is repeated to know the results of each party.

4.3 C LANGUAGE CODING:

[68]

#include<reg51.h> sfr input=0x90; sfr ldata=0xa0; sbit rs=P0^7;sbit rw=P0^6; sbit en=P0^5; sbit m=P3^0; sbit n=P3^1; sbit buzz=P3^2; sbit on=P3^3; void delay(int ); void lcdcmd(char ); void lcddata1(char *); void lcddata(char); void lcd(); int i1,i11,i12,i2,i21,i22,i3,i31,i32,i4,i41,i42,i5,i51,i52=0; void main() { on=0; P1=0;P3=0; while(1) { lcdcmd(0x38); delay(10); lcdcmd(0x0e) ; delay(10); lcdcmd(0x01); lcdcmd(0x06) ; delay(20) ; lcddata1("Vote"); if(n==1) on=1; if(m==1&on==1) { if (input==0x01) { buzz=1; while (input == 0x01); i1=i1 + 1;if(i1>=10)i11=i1/10; i12=i1%10; on=0; buzz=0; //ready=0; } if (input==0x02)

[69]

{buzz=1; while (input == 0x02); { i2=i2 + 1;if(i2>=10)i21=i2/10; i22=i2%10; on=0; buzz=0; } } if (input==0x04) { buzz=1; while (input ==0x04); { i3=i3 + 1;if(i3>=10)i31=i3/10; i32=i3%10; on=0; buzz=0; } } if (input==0x08) { buzz=1; while (input == 0x08); { i4=i4 + 1;if(i4>=10)i41=i4/10; i42=i4%10; on=0; buzz=0; } } if (input==0x10) { buzz=1; while (input == 0x10); { i5=i5 + 1;if(i5>=10)i51=i5/10; i52=i5%10;

[70]

on=0; buzz=0; } }} if(m==0)//else { if (input==0x01) { lcddata1(" CONGRESS="); lcddata(i11+0x30); lcddata(i12+0x30); delay(100); } if (input==0x02) { lcdcmd(0x01); lcddata1(" BJP="); lcddata(i21+0x30); lcddata(i22+0x30); delay(100); } if (input==0x04) { lcdcmd(0x01); lcddata1(" CPM&CPI="); lcddata(i31+0x30); lcddata(i32+0x30); delay(100); } if (input==0x08) { lcdcmd(0x01); lcddata1(" TDP="); lcddata(i41+0x30); lcddata(i42+0x30); delay(100); } if(input==0x10) { lcdcmd(0x01); lcddata1(" PRP="); lcddata(i51+0x30); lcddata(i52+0x30); delay(100); } else{

[71]

//lcdcmd(0x01); lcddata1("result"); delay(100) ; }} }} void delay(int time) { int i,j; for(i=0;i<time;i++) for(j=0;j<900;j++); } void lcdcmd(char value) { ldata=value; rs=0; rw=0; en=1; delay(2); en=0; } void lcddata1(char *value) { int i; for(i=0;value[i]!='\0';i++) { ldata=value[i]; rs=1; rw=0; en=1; delay(1); en=0; } } void lcddata(char value) { ldata=value; rs=1; rw=0; en=1; delay(1); en=0;

5. PROJECT METHODOLOGY[72]

5.1 Components:

Component Name Quantity

Microcontroller IC (AT89S52) 1 Transistor (L78O5CV) 1 Resistor 7 Diodes 4 Port Connectors 4 LED 3 Resistors 7 LCD (16X2 characters) 1 Buzzer 1 contrast controller 1push switches 10crystal oscillator 1

5.2 Software's used:

1. Keil uVision3. 2. Eclipse

5.3 Equipments used:

1. Soldering iron, solder, flux. 2. Personal computer. 3. DB25 connector.

6. RESULT AND CONCLUSION

The EVM consists of a microcontroller AT89S52 16×2 LCD display, LED ,push buttons, relay

and a buzzer.

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• In voting mode, the voting mode switch is in on condition.

• The EVM is ready for voting only after ready to vote button is pressed and the led is

on. The led turns off after a vote is casted along with a buzzer.

Counting the votes for individual candidate (5 in number) is done simultaneously

along with the voting and total number of votes cast to that individual can be checked

at anytime.

• In result mode, the voting mode switch is in off position.

• In result mode, the UNIT displays the votes of individual candidate, whenever the

“Result Button” of the corresponding individual is pressed.

In total, the complete system (including all the ha rdware components and software

routines) is working as per the initial specifications and requirements of our project.

Because of the creative nature of the design, and due to lack of time, some features could

not be fine-tuned and are not working properly. So certain aspects of the system can be

modified as operational experience is gained with it. As the users work with the system,

they develop various new ideas for the development and enhancement of the project.

7. APPLICATIONS

Fast track voting which could be used in small scale elections, like resident

welfare association, “panchayat” level election and other society level elections. It could also be

used to conduct opinion polls during annual share holders

meeting. It could also be used to conduct general assembly elections where number of

candidates are less than or equal to eight in the current situation.

8. FUTURE SCOPE

Number of candidates could be increased by using other microcontroller or an 8255

IC. It could be interfaced with printer to get the hard copy of the result almost instantly

from the machine itself. It could also be interfaced with the personal computer and result could be

stored in the central server and its backup could be taken on the other backend servers. Again, once

the result is on the server it could be relayed on the network to various

offices of the election conducting authority. Thus our project could make the result

available any corner of the world in a matter of seconds

9. REFRENCES AND BIBLOGRAPHY

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Muhammad Ali Mazidi , Janice Gillispie Mazidi, Rolin D. Mckinlay.

Second edition, “THE 8051 MICROCONTROLLER AND EMBEDDED

SYSTEM”

K. J. Ayala. Third edition, “The 8051 MICROCONTROLLER”

General information about electronic voting machine

www.eci.gov.in

www.eci.gov.in/faq/evm.asp

ww.eci.gov.in/Audio_VideoClips/presentation/EVM.ppt

www.rajasthan.net/election/guide/evm.htm

www.indian-elections.com/electoralsystem/electricvotingmachine.html

Tutorial on microcontroller:

www.8051projects.net/microcontroller_tutorials/

Tutorial on LCD:

www.8051projects.net/lcd-interfacing/

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