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Electronic Voting Machine

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India is the 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.

In India, all earlier elections are it state elections or center 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.

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This is a long, time-consuming process and very much prone to errors. This situation continued until the election scene was completely changed by an 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 a 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 center. It is also eco friendly. Our EVM consists mainly of two units – (a) Control Unit (CU) and (b) Ballot Unit (BU) with cable for connecting it with the Control unit.

Both units consist of one microcontroller (8052) each. The CU consists of one LCD, one hex keypad, and a couple of switches, while BU consists of a candidate panel, a vote cast panel, and a buzzer, etc. This project is based on assembly language programming. The software platform used in this project is Keil uVision3 and SPIPGM37.


Democracy And Voting Democracy has come to be accepted as the most preferred form of the political system all over the world. However, the success of a democratic structure is to be judged by the successes that can be solely attributed to this system. There are various challenges before democracy.

These are foundational challenges, the challenge of expansion, and the deepening of democracy. All of these are dependent on how democracy is perceived by people who form the government, participate in the formation of the government and are benefiting from it. As we all know that India is the 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. India follows a federal form of government. It means that government 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 a vast and complex system of governance? One needs not to be an Einstein to guess the answer. It is a fundamental right to vote or simply voting in elections. Indian constitution provides 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 the backbone of not just democracy in India but all around the world.

Voting can be done in various ways. In the early Roman Empire voting used to be done by raising hands in favor or against. In board rooms voting is done in a similar way, some write their vote down, some choose to speak, some choose to cast vote using the latest technology. Voting Techniques In India all earlier elections be it state elections or center 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 the 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 until the election scene was completely changed by the 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 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 the Control unit. A Balloting Unit caters up to 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 an 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, the 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 cardboard 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 blue button placed in front of your favorite candidate and release. As soon as the button is pressed, the red LED indicator lights up and a whistling sound comes from the machine.

This signifies that your vote has been cast rightly. Now you can come out. In case of red LED not working, press the Blue button firmly again. If finding it difficult, consult the Presiding Officer. Your vote is completely 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. What Happens after Voting is over?

After the hour fixed for the close of the poll and the last voter has recorded his vote, the EVM is closed so that no further recording of votes in the machine is possible. At the counting place, only the control unit is required for ascertaining the result of poll at the polling station at which the EVM was used. The balloting unit is not required. All this used to happen every time election was held. 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 be capable of recording a maximum of five votes per minute. (The pace of polling can be set to any predetermined number before manufacturing.) Thus, even for recording about 100 bogus votes it would take the booth captors 20 to 25 minutes, during which time the law and order officials may intervene to stop the rot. Moreover, as soon as the presiding officer apprehends any mischief, he can stop the poll by pressing the special switch after which no votes can be recorded.

The presiding officer of the polling station is empowered to close the control unit of the voting machine to ensure “that no further vote can be recorded. ” There is no possibility of any bogus votes being polled after the close of the poll and during the transit of the machines from the polling booth to the counting center. A vote once recorded in an EVM cannot be tampered with, whereas in the ballot paper system the votes marked and put into the box can be pulled out and destroyed. The EVMs are capable of retaining the memory of the votes recorded for a period of three years.

If the machine is tampered with in any respect either during the poll time or at any time before the counting of votes, which will be easily detectable so that a fresh poll can be ordered. 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’ expenditures, etc.
  • easy and accurate counting without any mischief at the counting center co friendly.

As a matter of interest, “Diebold Accuvote System”, is a smarter system over conventional EVMs used in India. It is a new system of voting adopted by the US government is DIEBOLD. Diebold system works on Microsoft software; it has no seals on locks and panels to detect a tempering. It has a keyboard interface (!!! ) and the server was tested to have the “Blaster” virus. One report on Wired says a lady stumbled upon some files from Diebold and found that the votes were stored in MS Access files. It also has a PCMCIA Scandisk card for local storage.

A touch screen GUI and a network connection to send the results to a server after encrypting it with DES. Compare and Contrast: Paper Voting, EVM and Diebold 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:

  • Device type

Ballot paper: Papers and boxes

EVM: Embedded system with Assembly code

Diebold: Embedded system with Windows CE, and C++ code

  • Visual Output

Ballot paper: Stamp on paper

EVM: Single LED against each candidate’s name

Diebold: Color Touch screen, with GUI software Operating

  • System/ Software

Ballot paper: No operating system

EVM: None, the Assembly code to register a number of votes is all it has Hence it is simple automation of voting, no complexities.

Diebold: Windows CE, and C++ code stored on the Internal Memory and PCMCIA cards, bulky, unnecessary additions.

  • 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.

Diebold: Internal ribbon printer. And PCMCIA storage for records and audit trials. Additionally the GEMS server also stores the votes and audits. Again unnecessary addition, work can be accomplished by a simple counter.

  • 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.

Diebold: Complex automatic operation. Two GEMS servers one primary and a backup, for every polling station, that connects to the voting units to “load the ballots” and then voting units work independently.

  • 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 afterward.

Diebold: GEMS servers have access through Supervisory Smart cards, and PINs, some users have a login and password access. But these server connections can be easily tapped and can be used for tempering with the data or procedure.

  • Ballot Issue

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

EVM: Ballot is issued by the 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.

Diebold: Voter access smart card is issued in an envelope for a terminal. A voter can put it in the assigned terminal and cast his/her vote. These smart card system rarely use encryption and hence it is not difficult o duplicate these cards and pose false identities.

  • Storage of Votes

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

EVM : In Internal Nonremovable memory of the Control Units. No transfer over the network. Security increases with this feature. Moreover, these results cant be accessed by authorized personnel only at commissioned offices..

Diebold: In a PCMCIA card hidden in the Voting Unit. Results are “transmitted” using modems to the counting center. Transmitting data over the network is very risky, not the best means of the result.

  • 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$) for one EVM. Diebold : About 3300$.

  • Power Supply

Ballot paper: No power supply required.

EVM: 6V alkaline batteries or electricity.

Diebold: Only electricity, means system will crash in case of power failure.

  • Capacity

Ballot paper: As much a ballot box can hold.

EVM: 3840 Votes .

Diebold: Over 35000 votes.

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, a peripheral interface, etc.
  • No security against illegal viewing of results, as a presiding officer, can view the results without any difficulty.
  • Less user friendly due to two seven-segment displays
  • Existing system costs around 12000 INR(300$)

Proposed System All these faults motivated us to make this new enhanced EVM. The faults which are eliminated are summarized as follows:

  • Microcontrollers replaced microprocessors, which made the EVM closer to real-time operation making it faster, more reliable, and unique.
  • Password protection is provided to save data from being accessed by unauthorized personnel. The presiding officer can only conduct voting process, doesn’t have any access over results.
  • More user-friendly and interactive LCD display
  • Proposed system costs around 2000 INR



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 the production of microprocessors, and the first computers were made by adding external peripherals such as memory, input-output lines, timers, and others. Further increasing of the volume of the package resulted in the creation of integrated circuits. These integrated circuits contained both processors and peripherals.

That is how the first chip containing a microcomputer, or what would later be known as a microcontroller came about.


It was the 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 a 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, the first 8-bit microprocessor appeared on the market under a name 8008. It was able to address 16Kb of memory, and it had 45 instructions and the speed of 300 000 operations per second. That microprocessor was the predecessor of all today’s microprocessors. Intel kept their developments up in April of 1974, and they put on the market the 8-bit processor under a name 8080 which was able to address 64Kb of memory, and which had 75 instructions, and the price began at $360.

In another American company Motorola, they realized quickly what was happening, so they put out on the market an 8-bit microprocessor 6800. Chief constructor was Chuck Peddle, and along with the processor itself, Motorola was the first company to make other peripherals such as 6820 and 6850. At that time many companies recognized greater importance of microprocessors and began their own developments. Chuck Peddle left Motorola to join MOS Technology and kept working intensively on developing microprocessors. At the WESCON exhibit in the United States in 1975, a critical event took place in the history of microprocessors.

The MOS Technology announced it was marketing microprocessors 6501 and 6502 at $25 each, which buyers could purchase immediately. This was so sensational that many thought it was some kind of a scam, considering that competitors were selling 8080 and 6800 at $179 each. As an answer to its competitor, both Intel and Motorola lowered their prices on the first day of the exhibit down to $69. 95 per microprocessor. Motorola quickly brought suit against MOS Technology and Chuck Peddle for copying the protected 6800. MOS Technology stopped making 6501 but kept producing 6502.

The 6502 was an 8-bit microprocessor with 56 instructions and a capability of directly addressing 64Kb of memory. Due to low cost, 6502 becomes very popular, so it was installed into computers such as KIM-1, Apple I, Apple II, Atari, Commodore, Acorn, Oric, Galeb, Orao, Ultra, and many others. Soon appeared several makers of 6502 (Rockwell, Sznertek, GTE, NCR, Ricoh, and Commodore takes over MOS Technology) which was at the time of its prosperity sold at a rate of 15 million processors a year! Others were not giving up though. Frederico Faggin leaves Intel and starts his own Zilog Inc. In 1976 Zilog announced the Z80.

During the making of this microprocessor, Faggin made a pivotal decision. Knowing that a lot of programs have been already developed for 8080, Faggin realized that many would stay faithful to that microprocessor because of great expenditure which redoing of all of the programs would result in. Thus he decided that a new processor had to be compatible with 8080, or that it had to be capable of performing all of the programs which had already been written for 8080. Besides these characteristics, many new ones have been added, so that Z80 was a very powerful microprocessor in its time.

It was able to address directly 64 Kb of memory, it had 176 instructions, a large number of registers, a built-in option for refreshing the dynamic RAM memory, single-supply, greater speed of work etc. Z80 was a great success and everybody converted from 8080 to Z80. It could be said that Z80 was without a doubt commercially most successful 8-bit microprocessor of that time. Besides Zilog, other new manufacturers like Mostek, NEC, SHARP, and SGS also appeared. Z80 was the heart of many computers like Spectrum, Partner, TRS703, Z-3. In 1976, Intel came up with an improved version of an 8-bit microprocessor named 8085.

However, Z80 was so much better than Intel soon lost the battle. Although a few more processors appeared on the market (6809, 2650, SC/MP etc. ), everything was actually already decided. There weren’t any more great improvements to make manufacturers convert to something new, so 6502 and Z80 along with 6800 remained as main representatives of the 8-bit microprocessors of that time.

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 a 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 Assembly language is often used in microcontrollers and since they usually follow RISC architecture, the instruction set is small. The development package of microcontrollers often includes an assembler, a simulator, a programmer to “burn” the chip and a demonstration board.

Some packages include a high-level language compiler such as a C compiler and ore sophisticated libraries. Most microcontrollers will also combine other devices such as:

  • A Timer module to allow the microcontroller to perform tasks for certain time periods.
  • A serial I/O port to allow data to flow between the microcontroller and other devices such as a PC or another microcontroller.
  • An ADC to allow the microcontroller to accept analog input data for processing.
  • Figure 2. 1: Showing a typical microcontroller device and its different subunits The heart of the microcontroller is the CPU core. In the past, this has traditionally been based on an 8-bit microprocessor unit.

Microcontrollers versus Microprocessors

Microcontroller differs from a microprocessor in many ways. The first and 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 the microprocessor is the very heart of the computer. On the other hand, the 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.

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 can not 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. Figure2. 2: Simplified model of a memory unit Memory components are exactly like that.

For a certain input, we get the contents of a certain addressed memory location and that’s all. Two new concepts are brought to us: addressing and memory location. Memory consists of all memory locations, and addressing is nothing but selecting one of them. This means that we need to select the desired memory location on one hand, and on the other hand we need to wait for the contents of that location. Besides reading from a memory location, memory must also provide for writing onto it. This is done by supplying an additional line called the control line.

We will designate this line as R/W (read/write). The Control line is used in the following way: if r/w=1, reading is done, and if the opposite is true then writing is done on the memory location. Memory is the first element, and we need a few operations of our microcontroller. The amount of memory contained within a microcontroller varies between different microcontrollers. Some may not even have an integrated memory (e. g. Hitachi 6503, now discontinued). However, most modern microcontrollers will have integrated memory. The memory will be divided up into ROM and RAM, with typically more ROM than RAM.

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).

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 the “central processing unit” (CPU). Its memory locations are called registers. Figure2. 3: Simplified central processing unit with three registers Registers are therefore memory locations whose role is to help with performing various mathematical operations or any other operations with data wherever data can be found.

Look at the current situation. We have two independent entities (memory and CPU) that are interconnected, and thus any exchange of data is hindered, as well as its functionality. If, for example, we wish to add the contents of two memory locations and return the result again back to memory, we would need a connection between memory and CPU. Simply stated, we must have some “way” through data that goes from one block to another.


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. The first one serves to transmit address from CPU memory, and the second to connect all blocks inside the microcontroller. Figure2. 4: Showing the connection between memory and central unit using buses As far as functionality, the situation has improved, but a new problem has also appeared: we have a unit that’s capable of working by itself, but which does not have any contact with the outside world, or with us!

In order to remove this deficiency, let’s add a block that contains several memory locations whose one end is connected to the data bus, and the other has a connection with the output lines on the microcontroller which can be seen as pins on the electronic component.

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. Figure2. : Simplified input-output unit communicating with the external world When working with it the port acts like a memory location. Something is simply being written into or read from it, and it could be noticed on the pins of the microcontroller.

Serial Сommunication

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 that 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 for the exchange of data. These rules are called a protocol. The 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. Once the transfer starts, we lower the transmission line to logical “0” for a period of time (which we will designate as T), so the receiving side will know that it is receiving data, and so it will activate its mechanism for reception.

Let’s go back now to the transmission side and start putting logic zeros and ones onto the transmitter line in the order from a bit of the lowest value to a bit of the highest value. Let each bit stay online for a time period which is equal to T, and in the end, or after the 8th bit, let us bring the logical unit “1” back on the line which will mark the end of the transmission of one data. The protocol we’ve just described is called in professional literature NRZ (Non-Return to Zero). Figure2. 6: Serial unit sending data through three lines only

As we have separate lines for receiving and sending, it is possible to receive and send data (info. ) at the same time. So called full-duplex mode block which enables this way of communication is called a serial communication block. Unlike the parallel transmission, data moves here bit by bit, or in a series of bits that define the term serial communication comes from. After the reception of data we need to read it from the receiving location and store it in memory as opposed to sending where the process is reversed. Data goes from memory through the bus to the sending location, and then to the receiving unit according to the protocol.

Timer Unit

Since we have the serial communication explained, we can receive, send and process data. Figure2. 7: Timer unit generating signals in regular time intervals However, in order to utilize it in the industry we need a few additional 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 our time.


One more thing is requiring our attention is the flawless functioning of the microcontroller during its run-time. Suppose that as a result of some interference (which often does occur in industry) our microcontroller stops executing the program, or worse, it starts working incorrectly. Figure2. 8: Watchdog Of course, when this happens with a computer, we simply reset it and it will keep working.

However, there is no reset button we can push on the microcontroller and thus solve our problem. To overcome this obstacle, we need to introduce one more block called watchdog. This block is in fact another free-run counter where our program needs to write a zero in every time it executes correctly. In case that program gets “stuck”, zero will not be written in, and counter alone will reset the microcontroller upon achieving its maximum value. This will result in executing the program again, and correctly this time around.

That is an important element of every program to be reliable without man’s supervision.

Analog to Digital Converter

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 that 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 information about some analog value to a binary number and for following 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.

The chart on the following page represents the center section of a microcontroller. Figure2. 11: Microcontroller outline with basic elements and internal connections For a real application, a microcontroller alone is not enough. Besides a microcontroller, we need a program that would be executed and a few more elements that make up interface logic towards the elements of the regulation (which will be discussed in later chapters).

Introduction to EEPROM


EEPROM means Electrical Erasable Programmable Read-Only Memory and also referred to as E.

PROM chip or i2c. As the name suggests, an EEPROM can be both erased and programmed with electrical pulses from a programmer kit, burner or the equipment itself. Since it can be both electrically written into and electrically erased, the EEPROM IC can be quickly programmed and erased in the circuit for reprogramming without taking them out from the mainboard. EEPROM IC is also called a non-volatile memory because when the power is switched off, the stored data (information) in the EEPROM IC will not be erased or corrupt and the data is still intact.

New EEPROM IC has no data (blank) inside and normally have to program it first with programmer tools before it can be use on an electron IC circuit. Figure3. 1: Showing EEPROM of Atmel If you just installed a new or blank EEPROM IC into a mainboard, even though with the same part number, I can say that the equipment will surely not going to work because the CPU or microprocessor do not know how to function. Information or data stored in this type of memory can be retained for many years even without a continuous dc power supply to the IC.

Application/ Operation of EEPROM

EEPROMs mainly store user-programmable information such as VCR programming information or data. CD programming information or data. Digital satellite receiver control data or information. User information on various consumer products such as in Television. The EEPROM IC in Computer Monitor performs two tasks:

  • When a monitor is turn on it will copies all the data or information from the EEPROM to the microprocessor or CPU. For instance, the EEPROM will let the CPU know the frequencies at which the monitor is going to run. The EEPROM IC is used to store the current settings of the Monitor.
  • The current settings of the monitor will not be erased even when the monitor is switched off. Anytime when a change is made in the monitor settings, the CPU updates the setting in the EEPROM (store data in EEPROM). When the monitor is switch on again, the stored settings in EEPROM IC are used to set up the monitor for operation. Assuming the data file in MONITOR or TV’s EEPROM are corrupted damaged and failure detected, what would be the display symptoms like. There would be no high voltage (no display) because the CPU don’t activate the 12-volt line supply to the horizontal and vertical oscillator IC. The IC will not save (store) the current setting of the equipment. Some control functions like sound, brightness, horizontal size, and contrast control will not work. The On-Screen Display (OSD) would not work or the OSD will have a corrupted or erratic display. Equipment high voltage will shut down (EEPROM set wrongly the horizontal frequency and will lead to a failure of the horizontal output transistor (HOT)). Typical EEPROM part numbers are: – 2402, 2404, 2408 24C02, 24C04, 24C08, 24C16 24C325, 24C645AT17C65, AT17C128 93C06, 93C46, 93C56, 93C66 5010, 25020, 25040

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.

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.

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 an 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 the next command or data and BF = 0 means LCD is ready for the next command or data to process.

Instruction Register (IR) and Data Register (DR)

There are two 8-bit registers controller Instruction and a 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 into the data register, and data is then moved automatically to the DDRAM and hence is displayed on the LCD.

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.

Sending Commands to LCD

To send commands we simply need to select the command register. Everything is the 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
  • Send enable signal
  • Wait for LCD to process the command

Introduction to I2C BUS

Basic Definition

An Inter-IC bus is often used to communicate across circuit-board distances.

At the low end of the spectrum of communication options for “inside the box” communication is I2C (“eye-squared-see”). The name I2C is shorthand for a standard Inter-IC (integrated circuit) bus. I2C provides good support for communication with various slow, on-board peripheral devices that are accessed intermittently while being extremely modest in its hardware resource needs. It is a simple, low-bandwidth, short-distance protocol. Most available I2C devices operate at speeds up to 400Kbps, with some venturing up into the low megahertz range. I2C is easy to use to link multiple devices together since it has a built-in addressing scheme.

Philips originally developed I2C for communication between devices inside of a TV set. Examples of simple I2C-compatible devices found in embedded systems include EEPROMs, thermal sensors, and real-time clocks. I2C is also used as a control interface to signal processing devices that have separate, application-specific data interfaces. For instance, it’s commonly used in multimedia applications, where typical devices include RF tuners, video decoders and encoders, and audio processors. In all, Philips, National Semiconductor, Xicor, Siemens, and other manufacturers offer hundreds of I2C-compatible devices.

Inside the Box

I2C is appropriate for interfacing to devices on a single board, and can be stretched across multiple boards inside a closed system, but not much further. An example is a host CPU on a main embedded board using I2C to communicate with user interface devices located on a separate front panel board. A second example is SDRAM DIMMs, which can feature an I2C EEPROM containing parameters needed to correctly configure a memory controller for that module. I2C is a two-wire serial bus. There’s no need for chip select or arbitration logic, making it cheap and simple to implement in hardware. Figure5.I2C has two lines in total The two I2C signals are serial data (SDA) and serial clock (SCL). Together, these signals make it possible to support the serial transmission of 8-bit bytes of data-7-bit device addresses plus control bits-over the two-wire serial bus. The device that initiates a transaction on the I2C bus is termed the master. The master normally controls the clock signal. A device being addressed by the master is called a slave. In a bind, an I2C slave can hold off the master in the middle of a transaction using what’s called clock stretching (the slave keeps SCL pulled low until it’s ready to continue).

Most I2C slave devices don’t use this feature, but every master should support it. The I2C protocol supports multiple masters, but most system designs include only one. There may be one or more slaves on the bus. Both masters and slaves can receive and transmit data bytes. Each I2C-compatible hardware slave device comes with a predefined device address, the lower bits of which may be configurable at the board level. The master transmits the device address of the intended slave at the beginning of every transaction. Each slave is responsible for monitoring the bus and responding only to its own address.

This addressing scheme limits the number of identical slave devices that can exist on an I2C bus without contention, with the limit set by the number of user-configurable address bits (typically two bits, allowing up to four identical devices).


As you can see in Figure 2, the master begins the communication by issuing the start condition (S). The master continues by sending a unique 7-bit slave device address, with the most significant bit (MSB) first. The eighth bit after the start, read/not-write (), specifies whether the slave is now to receive (0) or to transmit (1).

This is followed by an ACK bit issued by the receiver, acknowledging receipt of the previous byte. Then the transmitter (slave or master, as indicated by the bit) transmits a byte of data starting with the MSB. At the end of the byte, the receiver (whether master or slave) issues a new ACK bit. This 9-bit pattern is repeated if more bytes need to be transmitted. Figure5. 2: I2C communication In a write transaction (slave receiving), when the master is done transmitting all of the data bytes it wants to send, it monitors the last ACK and then issues the stop condition (P).

In a read transaction (slave transmitting), the master does not acknowledge the final byte it receives. This tells the slave that its transmission is done. The master then issues the stop condition.

A Simple Bus

As we’ve seen, the I2C signaling protocol provides device addressing, a read/write flag, and a simple acknowledgment mechanism. There are a few more elements to the I2C protocol, such as general call (broadcast) and 10-bit extended addressing. Beyond that, each device defines its own command interface or address-indexing scheme. Standard I2C devices operate up to 100Kbps, while fast-mode devices operate at up to 400Kbps.

A 1998 revision of the I2C specification (v. 2. 0) added a high-speed mode running at up to 3. 4Mbps. Most of the I2C devices available today support 400Kbps operation. Higher-speed operation may allow I2C to keep up with the rising demand for bandwidth in multimedia and other applications. Most often, the I2C master is the CPU or microcontroller in the system. Some microcontrollers even feature hardware to implement the I2C protocol. You can also build an all-software implementation using a pair of general-purpose I/O pins (single master implementations only).

Since the I2C master controls transaction timing, the bus protocol doesn’t impose any real-time constraints on the CPU beyond those of the application. (This is in contrast with other serial buses that are timeslot-based and, therefore, take their service overhead even when no real communication is taking place. )

The Elegance of I2C

I2C offers good support for communication with onboard devices that are accessed on an occasional basis. I2C’s competitive advantage over other low-speed short-distance communication schemes is that it’s cost and complexity don’t scale up with the number of devices on the bus.

On the other hand, the complexity of the supporting I2C software components can be significantly higher than that of several competing schemes (SPI and Micro Wire, to name two) in a very simple configuration. With its built-in addressing scheme and straightforward means to transfer strings of bytes, I2C is an elegant, minimalist solution for modest, “inside the box” communication needs.

Cite this Electronic Voting Machine

Electronic Voting Machine. (2016, Nov 22). Retrieved from https://graduateway.com/electronc-voting-machine/

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