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Semester Project Report

KEYPAD & LCD INTERFACEPrepared by

Zeeshan Maqbool 2008-EE-031

Imran Akhter 2008-EE-040

Muhammad Sajid Ali 2008-EE-021

Teacher

Sir Numan Siddiqui

Department of Electronics Engg

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  ACKNOWLEDGEMENT

In the name of ALLAH the ALMIGHTY who

enabled us to complete this report successfully and helped us in the difficult moments

during the development of this report.

PREFACE

Gratitude to ALLAH ALMIGHTY (Azza-wa-Jal) and cordial tribute to Nabi-e-Karim (Sai-

Allah-Aliika-Wasalam) by the grace of which we achieve success in every field of life.

The project is compiled on a student level on the behalf of possible technical data

arranged from internet and from course book.

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KEYPAD & LCD INTERFACE

Project Objective

To design and implement a keypad interface with 8051 which print the

character on LCD pressed from the keypad.

Working 

.

Microcontrollers are just silicon wafers until we tell them what to do, programthem

according to our requirement. Similarly any user interface is incomplete without an

Input. One, two pushbuttons can be easily interfaced however if more user inputs are

required it can take up a lot of I/O lines. So here is a small tutorial to interface a 4x4

Matrix Keypad and displaying the key pressed on a LCD. Themicrocontroller used is

AT89C51 and the coding has been done in assembly language.

The 4x4 Keypad has 16 keys and requires a single PORT or 8 I/O lines. Port 3 has

been designed to handle keypad, LCD Data Bus D7-D0 is connected to PORT 1, while

(Enable) EN is connected to P2.0

(Register Select – Command or Data Register) RS is connected to P2.1

(Read/Write) RW is connected to P2.2

The LCD is based on Hitachi HD44780 Controller and

To check for the keystroke, a polling method has been used.

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PORT 3.0 Key 1 Key 2 Key 3 Key 4

PORT3.1 Key 5 Key 6 Key 7 Key 8

PORT3.2 Key 9 Key 10 Key 11 Key 12

PORT3.3 Key 13 Key 14 Key 15 Key 16

PORT3.4 PORT3.5 PORT3.6 PORT3.7

The connections are similar as shown over here. Now consider this, if I select the first

column only, it has 4 keys, 1, 5,9,13. If a change of value (i.e. Binary 1 or 0) is made

any one of these keys, it can be decoded and suitable message is displayed on the

LCD. This is exactly what happens. Initially all the I/O lines are pulled high, then during

Key Scan, every column linked is held low for a little time. If during that time a Key is

pressed in that column a row I/O lines is also held low, thus the keystroke can

be captured.

The obvious question would be what if we press the key on a particular column and at

that particular moment that column has not been pulled low, thus making no signal

changes?

The answer is simple, the microcontroller runs quite fast, even a convention 89c51 in

which the internal frequency= external frequency clock/12 can achieve 2 MIPS at

24MHz. That is 2 Million instructions Per Second. This method is not foolproof, it has a

drawback, while the Key Scan, It cannot perform other cumbersome operations which

may take time and a Key Stroke could be missed. The program will work very well for

small operations like activating a small relay or LED when a Key is pressed, but forpeople who want their systems to be near to perfect they may utilize other method.

.

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Block diagram

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Circuit Diagram

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Flow Chart

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Coding

ORG 00H

MOV A,#38H ;INITIATE LCD

CALL CWRT ;COMMAND SUBROUTINE

CALL DELAY

MOV A,#0EH ;DISPLAY ON,CURSOR ON

CALL CWRT

CALL DELAY

MOV A,#01H ;CLEAR LCD

CALL CWRT

CALL DELAY

MOV A,#06H ;SHIFT CURSOR RIGHT

CALL CWRT

CALL DELAY

MOV P3,#0FFH ;MAKE P3 AN INPUT PORT

K1:

MOV P1,#0 ;GROUND ALL ROWS AT ONCE

MOV A,P3 ;READ ALL COL.

ANL A,#00001111B ;MASKED UNUSED BIT

CJNE A,#00001111B,K1 ;CHECK TILL ALL KEYS RELEASED

K2:

ACALL DELAY ;CALL 20 MS DELAY

MOV A,P3 ;SEE IF ANY KEY IS PRESSED

ANL A,#00001111B ;MASKED UNUSED BIT

CJNE A,#00001111B,OVER ;KEY PRESSED, WAIT CLOSURE

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SJMP K2 ;CHECK TILL KEY PRESSED

OVER:

ACALL DELAY ;WAIT 20 MS DEBOUNCE TIME

MOV A,P3 ;CHECK KEY CLOSURE

ANL A,#00001111B ;MASKED UNUSED BIT

CJNE A,#00001111B,OVER1 ;KEY PRESSED, FIND ROW

SJMP K2 ;IF NONE, KEEP POLLING

OVER1:

MOV P1,#1111110B ;GROUND ROW 0

MOV A,P3 ;READ ALL COLUMNS

ANL A,#00001111B ;MASKED UNUSED BIT

CJNE A,#00001111B,ROW_0 ;KEY ROW 0, FIND THE COL

MOV P1,#11111101B ;GROUND ROW 1

MOV A,P3 ;READ ALL COL.

ANL A,#00001111B ;MASKED UNUSED BIT

CJNE A,#00001111B,ROW_1 ;KEY ROW 1, FIND THE COL

MOV P1,#11111011B ;GROUND ROW 2

MOV A,P3 ;READ ALL COL.

ANL A,#00001111B ;MASKED UNUSED BIT

CJNE A,#00001111B,ROW_2 ;KEY ROW 2, FIND THE COL

MOV P1,#11110111B ;GROUND ROW 3

MOV A,P3 ;READ ALL COL.

ANL A,#00001111B ;MASKED UNUSED BIT

CJNE A,#00001111B,ROW_3 ;KEY ROW 3, FIND THE COL

LJMP K2 ;IF NONE, FALSE INPUT, REPEAT

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ROW_0:

MOV DPTR, #KCODE0 ;SET DPTR=START OR ROW 0

SJMP FIND ;FIND COLUMN BELONGS TO

ROW_1:

MOV DPTR, #KCODE1 ;SET DPTR=START OR ROW 1

SJMP FIND ;FIND COLUMN BELONGS TO

ROW_2:

MOV DPTR, #KCODE2 ;SET DPTR=START OR ROW 2

SJMP FIND ;FIND COLUMN BELONGS TO

ROW_3:

MOV DPTR, #KCODE3 ;SET DPTR=START OR ROW 3

FIND:

RRC A ;SEE IF ANY CY BIT LOW

JNC MATCH ;IF ZERO GET ASCII CODE

INC DPTR ;POINT TO NEXT COLUMN

SJMP FIND ;KEEP SEARCHING

MATCH:

CLR A

MOVC A,@A+DPTR ;GET ASCII CODE FROM LOOK-UP

 //CALL DWRT ;CALL LCD DATA WRITE ROUTINE

MOV P2,A

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LJMP K1 ;LOOP

DELAY:

dl1:MOV R4,#62

MOV R5,#149

DJNZ R5,$

DJNZ R4,dl1

ret

CWRT:

MOV P2,A ;COPY REGISTER TO PORT 2

CLR P0.0 ;RS=0 FOR COMMAND

CLR P0.1 ;W/R=0 FOR WRITE

SETB P0.2 ;E=1

CALL DELAY

CLR P0.2 ;E=0

ret

DWRT:

MOV P2,A

SETB P0.0 ;RS=1 FOR DATA

CLR P0.1 ;R/W=0 FOR WRITE

SETB P0.2 ;E=1

CALL DELAY

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CLR P0.2 ;E=0

ret

;LOOK-UP TABLE

ORG 300H

KCODE0:

DB '0' , '1' , '2' , '3' ;ROW 0

KCODE1:

DB '4' , '5' , '6' , '7' ;ROW 1

KCODE2:

DB '8' , '9' , 'A' , 'B' ;ROW 2

KCODE3:

DB 'C' , 'D' , 'E' , 'F' ;ROW 3

END 

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Data Sheet

CONCLUSION 

TIME [MAN HOURS] CONSUMED 

Total time consumed on the project is 8-10 hours.

SOURCE OF COMPONENTS 

First we searched on internet about project aeecssories and then brought

from electronics market .

For Use by the Teacher Only 

Marks/Grade Obtained:

Teacher’s Comments: 

Name: miss umaira shahid

Signature:

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A resistor is a two-terminal passive electronic componentwhich

implements electrical resistance as a circuit element. When a voltage V is

applied across the terminals of a resistor, a current I will flow through theresistor in direct proportion to that voltage.

by Ohm's law: 

Resistors are common elements of electrical networks and electronic

circuits and are ubiquitous in most electronic equipment.

unitThe ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg

Simon Ohm. An ohm is equivalent to a volt per ampere. Since resistors are

specified and manufactured over a very large range of values, the derived

units of milliohm (1 mΩ = 10−3 Ω), kilohm (1 kΩ = 103 Ω), and megohm (1 MΩ

= 106 Ω) are also in common usage 

A capacitor (formerly known as condenser) is a device for storingelectric charge. Capacitors used as parts of electrical systems, for example,

consist of metal foils separated by a layer of insulating film.

Capacitors are widely used in electronic circuits for blocking direct

current while allowing alternating currentto pass, in filter networks, for

smoothing the output ofpower supplies, in the resonant circuits that tune

radios to particular frequencies and for many other purposes.

A crystal oscillatoris an electronic oscillator circuit that uses the

mechanical resonance of a vibrating crystal ofpiezoelectric material to create

an electrical signal with a very precise frequency. This frequency is commonly

used to keep track of time (as in quartz wristwatches), to provide a

stable clock signal for digital integrated circuits, and to stabilize frequencies

for radio transmitters and receivers. Quartz crystals are manufactured for

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frequencies from a few tens of kilohertz to tens of megahertz. Most are used

for consumer devices such as wristwatches, clocks, radios,computers, 

and cellphones. 

Variable resistors consist of a resistance track with connections atboth ends and a wiper which moves along the track as you turn the spindle.

The track may be made from carbon, cermet (ceramic and metal mixture) or a

coil of wire (for low resistances). The track is usually rotary but straight track

versions, usually called sliders, are also available.

Variable resistors are often called potentiometers in books and catalogues.

They are specified by their maximum resistance, linear or logarithmic track,

and their physical size. The standard spindle diameter is 6mm. Some variable

resistors are designed to be mounted directly on the circuit board,

The Intel 8051 microcontroller is one of the most popular general

purpose microcontrollers in use today. The Intel 8051 is an 8-bit

microcontroller which means that most available operations are limited to 8

bits.

Some of the features that have made the 8051 popular are:

  64 KB on chip program memory.  128 bytes on chip data memory(RAM).

  4 reg banks.

  128 user defined software flags.

  8-bit data bus

  16-bit address bus

  32 general purpose registers each of 8 bits

  16 bit timers (usually 2, but may have more, or less).

  3 internal and 2 external interrupts.  Bit as well as byte addressable RAM area of 16 bytes.

  Four 8-bit ports, (short models have two 8-bit ports).

  16-bit program counter and data pointer.

  1 Microsecond instruction cycle with 12 MHz Crystal.

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8051 models may also have a number of special, model-specific features,

such as UARTs, ADC, OpAmps, etc...

The 8051 requires the existence of an external oscillator circuit. The oscillator

circuit usually runs around 12MHz, although the 8051 (depending on which

specific model) is capable of running at a maximum of 40MHz. Each machinecycle in the 8051 is 12 clock cycles, giving an effective cycle rate at 1MHz (for

a 12MHz clock) to 3.33MHz (for the maximum 40MHz clock).

A liquid crystal display (LCD) is a thin, flat electronic visual

display that uses the light modulating properties of liquid crystals (LCs). LCs

do not emit light directly.

They are used in a wide range of applications, includingcomputer

monitors, television, instrument panels, aircraft cockpit displays, signage, etc.They are common in consumer devices such as video players, gaming

devices, clocks, watches, calculators, and telephones. LCDs have

displaced cathode ray tube (CRT) displays in most applications.

A keypad is a set of buttons arranged in a block or "pad" which usually

bear digits, symbols and usually a complete set of alphabetical letters. If it

mostly contains numbers then it can also be called a numeric keypad.

Keypads are found on many alphanumeric keyboards and on other devices

such as calculators, push-button telephones, combination locks, and digital

door locks, which require mainly numeric input 

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Marks/Grade Obtained:

Teacher’s Comments: 

Name: miss umaira shahid

Signature: