Scroll Pad2

8/2/2019 Scroll Pad2

1/48

SUBMITTED BY:

Raman BediAmit SharmaAshish Dhiman

Arvind Chauhan

SCROLL PAD


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Implementation Environment

1. Microcontroller

The microcontroller we have used is AT89S52 which belongs to 8052 series of

microcontrollers and is a member of 8051 family. The 8052 has all the standard features

of 8051 as well as an extra 128 bytes of RAM and an extra timer. In other words, the

8052 has 256 bytes of RAM and 3 timers. It also has 8k bytes of on-chip ROM instead

of 4Kbytes. All programs written for the 851 will run on the 8052, but the reverse is not

true.

Feature 8051 8052

ROM (on-chip program space in bytes) 4K 8K

RAM (bytes) 128 256

Timers 2 3

I/O pins 32 32

Serial port 1 1

Interrupt sources 6 8

Table i: Comparison between 8051 and 8052

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Figure i: Pin configuration of Microcontroller

8052 micro controller has 4 ports. These are port0, port1, port2, port3 which can be

accessed as I/0 ports. The pins of the micro controller are explained below.

1. Reset: It resets total 8052 micro controller.

2. RXD: It receives data in serial communication.

3. TXD: It transmits data in serial communication.

4. INT0: External interrupt for timer 0.5. INT1: External interrupt for timer1

6. T0: Timer0.

7. T1: Timer1.

8. RD: To read into external memory.

9. WR: To write into external memory.

10. XTAL1 & XTAL2: To connect the crystal oscillator.

11. ALE: Address latch enable which is used to access the address locations

from external memory.

12. PSEN: Program store enable which is used for storing programming code

into the external memory.

13. EA: External Access: 64 KB of ROM is the limit for external memory.

The 8052 has an on-chip oscillator but requires an external clock to run it. A quartz

crystal oscillator is to be connected to the inputs XTAL1 (pin19) and XTAL2 (pin18).

The quartz crystal oscillator also needs two capacitors of 30 pF value.

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Figure ii: Oscillators connections.

The speed of 8052 refers to the maximum oscillator frequency connected to XTAL. For

example a 12-MHz chip must be connected to a crystal with 12 MHz frequency or less.We can observe the frequency on the

XTAL2 pin using the oscilloscope

RST: RESET pin is an input and is active high (normally low). Upon applying a high

pulse to this pin, the microcontroller will reset and terminate all activities. This is often

referred to as a power-on reset. Activating a power-on reset will cause all values in the

registers to be lost.

In order for the RESET input to be effective, it must have a minimum duration of 2

machine cycles. In other words, the high pulse must be high for a minimum of 2

machine cycles before it is allowed to go low.

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Figure iii: Reset circuitry.

EA, external access, is an input pin and must be connected to Vcc or GND. The 8051

family members all come with on-chip ROM to store programs. So, EA pin is connected

to Vcc.

The 8031 and 8032 family members do not have on-chip ROM, so code is stored on an

external ROM and is fetched by 8031/32. So, EA pin must be connected to GND to

indicate that the code is stored externally.

The following two pins are used mainly in 8031-based systems:

1. PSEN, program store enable, is an output pin. This pin is connected to

the OE pin of the ROM.

2. ALE, address latch enable, is an output pin and is active high.

Port 0 provides both address and data. The 8031 multiplexes address and data through

port 0 to save pins ALE pin is used for demultiplexing the address and data by

connecting to the G pin of the 74LS373 chip.

The four 8-bit I/O ports P0, P1, P2 and P3 each uses 8 pins. All the ports upon RESET

are configured as output, ready to be used as input ports.

Port 0 is also designated as AD0-AD7, allowing it to be used for both address and data.

When connecting an 8051/31 to an external memory, port 0 provides both address and

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data. The 8051 multiplexes address and data through port 0 to save pins. ALE indicates

if P0 has address or data

When ALE=0, it provides data D0-D7

When ALE=1, it has address A0-A7

It can be used for input or output, each pin must be connected externally to a 10K ohm

pull-up resistor. This is due to the fact that P0 is an open drain, unlike P1, P2, and P3.

Open drain is a term used for MOS chips in the same way that open collector is used for

TTL chips

Figure iv: Port 0 connections.

In 8051-based systems with no external memory connection, both P1 and P2 are used as

simple I/O. In 8031/51-based systems with external memory connections, port 2 must be

used along with P0 to provide the 16-bit address for the external memory.

P0 provides the lower 8 bits via A0 A7.

P2 is used for the upper 8 bits of the 16-bit address, designated as A8 A15, and it

cannot be used for I/O

Port 3 can be used as input or output

Port 3 does not need any pull-up resistors. It has the additional function of providing

some extremely important signals.

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Figure v: Port 3 pins.

1. Information Engineering

National Cheng Kung University 28HANEL

2. Software & Hardware used

As we know that the microcontroller is a programmable device and can perform or give

output as per the program burnt into it. The program can be burnt into it using a

programmer (hardware) and software installed in a computer. The program can be burnt

by connecting the COM port of the computer to the RS 232 port of the programmer

using DB9 connector. The programmer burns the program into the microcontroller

through its serial communication ports.

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Software for programming

ASM51

The programs were written in assembly language using notepad as an editor and weresaved with .asm as the extension. ASM51 is an assembler which assembles the files

with .asm in the folder and generates two files in the same folder with .hex and .list as

the extensions. The .hex file contains the hex conversion of the program and the .list file

contains the errors if any. It is the .hex file which is burnt into the microcontroller.

Software for Simulation

Proteus

Proteus is a simulating software which is used to make the circuits and then to check the

output according to the programming done. The hex file of the program is loaded into

the microcontroller used in the circuit and is simulated to check whether the output is

the desired one or not.

Software for burning programISP Flash Programmer 3.0a

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ISP Flash Programmer 3.0ais software for burning program into microcontroller. This

software basically acts as an interface for setting up the communication between the

computer and the programmer in which the microcontroller is plugged. Any one of the

COM ports can be used for communication. Usually COM 2 is used as COM 1 is used

by the mouse. The software can be set for programming different types of

microcontrollers. After setting it for the microcontroller being used, the hex file of the

program is loaded and is burnt into the microcontroller with the help of the programmer.

Figure ix: ASM51 working screen

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Figure x: Proteus working screen

Figure xi: ISP working screen

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Programmer kit

A programmer is used to burn the hex file into the ROM of the microcontroller. This

programmer can be connected to the COM port of the computer using DB9 connector.

The microcontroller is plugged into the socket and then the hex file is burnt into the

ROM of the microcontroller with the help of software mentioned above.

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Figure xii: Programmer kit

III. Work Done

1. LCD Interfacing

LCD

LCD stands for Liquid Crystal Display. It is basically used to display data replacing

LEDs (seven segment LEDs or multisegment LEDs). This is due to following reasons:

1. The declining prices of LCDs.

2. The ability to display numbers, characters and graphics.

3. Ease for programming for characters and graphics.

We have studied about 16*2 alphanumeric LCD which can display data in 2 lines.

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Figure xiii: 16*2 alphanumeric LCD

LCD pin description

Pin Symbol I/O Description1 VSS - Ground

2 VCC - +5V power supply

3 VEE - Power supply to control contrast

4 RS I RS=0 to select command register, RS=1 to select data

register.

5 R/W I R/W=0 for write, R/W=1 for read

6 E I/O Enable

7 PB0 I/O The 8 bit data bus

8 PB1 I/O The 8 bit data bus

9 DB2 I/O The 8 bit data bus






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Table i: LCD pin description

Interfacing LCD with MCU

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Figure xiv: Interfacing LCD with MCU

From the above picture it is clear that the data pins of the LCD are connected to P1 of

the microcontroller. The control pins i.e. RS, R/W and E of the LCD are connected to

P2.5, P2.4 and P2.3 respectively. The program for displaying SCROLL PAD on the

LCD is given below.

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acall delay

clr p2.3

ret

datawrt: mov p1, a ; Display subroutine.

setb p2.5

clr p2.4

setb p2.3

acall delay

clr p2.3

ret

delay: mov r2, #10

here2: mov r3, #255

here1: djnz r3, here1

djnz r2, here2

ret

org 0100h

db 'SCROLL PAD'

end

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4. Project Description

Scroll pad

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Introduction

What is Scroll pad?

It is 8052 based device which can type alphabets, numerals and some other charactersinto the LCD with just a finger scroll. The finger is to be scrolled on a particular pattern

made on the pad in the shape of the character you want to be type.

Need and use of Scroll pad?

Today we are living in the world full of hi-tech gadgets which perform different tasks

efficiently and with minimum human effort. Scroll pad is such a gadget although not so

hi-tech but good enough to sense the motion of a finger resembling English alphabets,

numerals and some other characters and displays the corresponding character on the

LCD fixed above it. Hence this scroll pad reduces human effort as compared to typing

the same text using a keyboard. Moreover with further advancements in this scroll pad,

the usage of the keyboards having large number of keys on it as compared to just few

touch sensors of the scroll pad can be eliminated.

Once the text has been written into the LCD, it can be transferred to a distant LCD for

data presentations. This facility can be used by the professors to deliver the lectures by

writing on the scroll pad in place of boards and then displaying the written data on a

distant LCD for the students to view it. Now, as the lecture delivered has been converted

into electrical form so it can be saved or can be converted into a hard copy.

The concept of sending the data from scroll pads LCD to a distant LCD can be used for

writing the data into the LCD or LED screens used as notice boards. Hence the data can

be written into these screens from a distant place and also without the use of computers.

These could be the few uses of the scroll pad, which could be increased in numbers with

the further advancements in it.

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Overview

Scroll pad is a set of ten touch sensors. Eight out of which are arranged in a particular

pattern and other two are used for giving commands. These are DISPLAY and

TRANSFER. All these touch sensors are made by using BC547 which is an npn

transistor. The pattern made by the arrangement of eight touch sensors senses the

motion of a finger being scrolled upon it. Once the scrolling is finished, touch

DISPLAY. If the motion of the finger resembles any of the English alphabets (A to Z)

or any of the numerals (0 to 9), then the corresponding character will displayed on the

LCD fixed above it. Along with the alphabets and numerals $, *, -, +, =, < and > can

also be sensed and displayed by the scroll pad. After the text has been written into the

LCD, it can be transferred to a distant LCD. The command for transmission is be given

with just a touch on TRANSFER.

Figure xix: Circuit Model of Scroll pad

Block Diagram of Scroll pad

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Figure xx: Block Diagram of Scroll Pad.

Touch Sensors

The touch sensors used here are made up of BC547 npn transistors. We know thatwhenever npn transistor in CE configuration is supplied with a small value of current at

its base terminal, it acts as a switch i.e. conduction between collector and emitter takes

place. This property of npn transistor is used here.

In a touch sensor, the current to the base is provided by the touch of a finger. The finger

should also be in contact with Vcc. Here, the conductive nature of human body comes

into play.

Now, here a question could arise that Can we use a conductor in place of finger?

The answer to the question is NO. Because if a conductor is used then the current

flowing into the base will not be in small amount and will destroy the transistor. In other

words, applying directly +5v to the base of npn transistor in CE configuration will

destroy it as a result of short circuit.

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Now, the circuit of this basic touch sensor is slightly modified in order to get a more

useful touch senssor which can be used in the main circuit.

Here, when the biasing is provided, the conduction between C and E takes place and the

output will be approximately 0v as all the voltage will drop across 10 k resistor. And

when the biasing is not provided, there will be no conduction between C and E and

hence the output will be approximately +5v.

The output we get from this touch sensor is in analog form whereas we require a digital

one. For this a comparator is used, which compares the analog voltage with a fixed

reference voltage and gives digital voltage which can be fed directly to the

microcontroller.

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Analog to digital conversion

The output of the sensor we get will be analog in nature. So, if we are using this output

to drive microcontroller, we will need to convert this to a digital signal first. That can be

done in two ways:

1. using comparators.

2. using ADCs(Analog-to-Digital Converters).

I will be using the comparator as its very easy to handle and also cheap. After the

comparator, we will get a signal that can be directly fed to the micro-controller.

Figure xxiii: LM324 Comparator

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Pin Diagram of LM324

This device consists of four independent precision voltage comparators with an offset

voltage specifications as low as 2mV. This comparator is designed to specifically

operate from a single power supply over a wide range of voltages. Operation from split

power supplies is also possible. This comparator also has aunique characteristic whichis that the input common-mode voltage range includes ground even though operated

from a single power supply voltage.

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Figure xxiv: Pin Diagram of LM324

Touch Sensor Circuit

Figure xxv: Touch Sensor circuit

The analog output that we get from the transistor will be compared with a fixed

reference voltage. This reference voltage is set by varying the slider of the

potentiometer. If the transistors ouptput voltage is greater than the reference voltage

then the outout will be +5v and viceversa. Hence, the analog voltage has been converted

into digital form which can be fed directly to the microcontroller.

In the scroll pad 10 touch sensors will be used. So, it is not convenient to touch the base

terminal of the transistors directly. Thus a surface for touch is developed on a copper

clad PCB using PCB printing technique. This has also helped in arranging the sensors

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according to a fixed pattern. The pattern developed on the PCB looks like the figure

shown below.

Figure xxvi: Scroll Pads Pattern.

As we can see that the red color represents Vcc. It is along this pattern the finger shouldbe scrolled. During scrolling the finger already touching Vcc will come in contact with

the two adjacent touch sensors. As the finger is moved, the set of two adjacent sensors

keep on changing. Hence, different signals will be generated while scrolling. These sets

of signals are continuously saved by the mic. At last the mic will display the

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corresponding character if the scrolled set matches with a stored set. The character will

be displayed only if DISPLAY is touched.

Once the character has been displayed, it can be sent to a distant LCD with the touch on

TRANSFER.

Microcontroller

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

8Kbytes of Flash Programmable and Erasable Read Only Memory (PEROM).

The device is manufactured using Atmels high density nonvolatile memory

Technology. The on-chip Flash allows the program memory to be reprogrammed in-

system or by a conventional nonvolatile memory programmer. By combining a versatile

8-bit CPU with Flash on a monolithic chip, the Atmel AT89S52 is a powerful

microcomputer which provides a highly flexible and cost effective solution to many

embedded control applications. The AT89S51 provides the following standard features:

8Kbytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, five

vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and

clock circuitry. In addition, the AT89S52 is designed with static logic for operation

down to zero frequency and supports two software selectable power saving modes. TheIdle Mode stops the CPU while allowing the RAM, timer/counters, serial port and

interrupt system to continue functioning. The Power down Mode saves the RAM

contents but freezes the oscillator disabling all other chip functions until the next

hardware reset.

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Onboard Pin Connections

Scroll Pad

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Circuit Diagram of SROLL PAD

Figure xxvii: Scroll Pad

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Construction Procedure of APSPS

Step 1: Circuit diagram of the proposed system is designed and finalized

Step 2: All the components and software platform to be used are selected which are also

mentioned above.

Step 3: The scroll pads pattern is designed and then developed on the copper clad PCB.

Step 4: All the hardware components are soldered on PCB with the help of soldering

ion, solder and flux.

Step 5: Code/program of the proposed system is developed using assembly language

with the help of software platform (Keil u vision3).The coding could be seen in section.

Step 6: The hex code of the program being created by the software platform is burnt

into the flash code memory of our microcontroller IC AT89C52.

Step 7: Testing is done at various levels to finalize the appropriate program for the most

proper working of the system.

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Program

Scroll Pad

; p0 =====> SCROLL PAD, is a matrix of 8 touch sensors to sense scrolling

; on 16 different lines. Each line is sensed by a set of 2 particular sensors.

; p2.0 =====> TRANSFER, is a touch sensor for transferring data from scroll

; pad's LCD to a distant LCD through RF communication.

; p2.1 =====> DISPLAY, is a touch sensor for comparing the lines being

; scrolled upon with the previously stored set of lines (representing different

; characters). And then displaying the corresponding character on scroll pad's LCD.

; p2.2 =====> LED, it glows after a line is being scrolled upon, while touching

; DISPLAY, TRANSFER and while transferring the data to a distant LCD.

; p2.3 =====> E (scroll pad's LCD)

; p2.4 =====> R/W (scroll pad's LCD)

; p2.5 =====> RS (scroll pad's LCD)

; p1 =====> Data Lines (scroll pad's LCD)

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;-------------------------------------------------------------------------------------------------------;-

------------------------------------------------------------------------------------------------------

$include(mod51)

org 0000h

mov p0, #0ffh ; For p0 as an i/p port.

lcall LCD_init

main: mov r1, #31h ; Initial RAM address where the

; lines being scrolled upon will be stored.

mov 30h, #0 ; Initialised to zero for comparison

; purposes.

mov r2, #0 ; Counter for counting the lines being

; scrolled upon.

again: mov dptr, #lines ; Dptr pointing the lines stored in ROM

; for comparison.

mov a, p0 ; Getting a byte from the scroll pad.

cjne a, #0ffh, line_match ; Checking for any touch

; on scroll pad.

jnb p2.1, label ; Checking for a touch on DISPLAY.

jnb p2.0, transfer; Checking for a touch on TRANSFER.

sjmp again

label: clr p2.2 ; LED is switched on, representing

; DISPLAY has been touched.

lcall delay2

jb p2.1, label1 ; Checking if DISPLAY is released.

sjmp label

label1: setb p2.2 ; LED is switched off, representing

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; DISPLAY has been released.

mov a, r2

cjne a, #0, label2 ; Checking the counter, if

; lines are stored in RAM.

sjmp again

label2: mov dptr, #characters ; Dptr ponting sets of lines (representing

; characters) stored in ROM.

sjmp ch_mtch_dsp

transfer: clr p2.2 ; LED is switched on, representing

; TRANSFER has been touched.

lcall delay2

jb p2.0, transfer1 ; Checking if TRANSFER is released.

sjmp transfer

transfer1: mov a, r7

cjne a, #0, transfer2 ; Checking the cursor's

; counter, if any character ;

is displayed on LCD.

setb p2.2

sjmp again

transfer2: mov r6, #41h ; Initial RAM address where the

; characters displayed (to be transferred)

; are be stored.

mov a, r7 ; Counter representing the number of

; characters have been displayed.

mov r3, a

inc r3

trsfr1: mov r4, #4

mov a, r6

mov r0, a

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mov a, @r0

trsfr: rrc a

mov p3.7, c ; Character is being transferred with 2

; bits at a time, starting from LSB.

rrc a

mov p3.6, c

clr p3.5

lcall delay1

setb p3.5

lcall delay1

djnz r4, trsfr

inc r6

djnz r3, trsfr1

setb p2.2

sjmp main

line_match: mov r3, a ; Storing the received byte.

mov r4, #0 ; Counter for line matching.

again1: mov a, r4

movc a, @a+dptr

cjne a, #0, match1 ; Checking for null

; character.

sjmp again

match1: clr c

subb a, r3

cjne a, #0, next_line ; Checking

; whether the line is

; matched.

clr p2.2 ; LED is switched on, representing a line

; has been scrolled upon.

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sjmp again1

;---------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------

ch_mtch_dsp: clr a

movc a, @a+dptr

mov r3, a ; Storing character.

mov a, #1

movc a, @a+dptr

mov r4, a ; Storing ROM counter.

clr c

subb a, r2

cjne a, #0, below5 ; Checking whether the

; counter is equal to that in r1.

mov r6, #2 ; For first line of the stored character.

again2: mov a, r1

mov r0, a ; Storing RAM address.

dec r0

mov a, r2

mov r5, a ; Storing RAM counter.

again3: mov a, r6

movc a, @a+dptr

cjne a, #0, match2 ; Checking for null char.

mov a, r3

cjne a, #'/', display ; '/' is for deleting the

; character.

mov a, r7

cjne a, #0, first_line ; Jump to main if the

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; cursor is at initial position.

ljmp main

below5: sjmp next_char

first_line: cjne a, #16, del_char1 ; Jump to last position of

; 1st line if the cursor is at

; 1st position of 2nd line.

mov a, #8fh

acall command

acall delay

sjmp del_char2

del_char1: mov a, #10h ; For deleting the character.

acall command

acall delay

del_char2: mov p1, #' '

setb p2.5

clr p2.4

setb p2.3

acall delay

clr p2.3

mov a, #10h

acall command

acall delay

dec r7

dec 40h

stay: mov a, p0

cjne a, #0ffh, below1

jnb p2.1, below2

jnb p2.0, below3

sjmp stay ; Stay here untill DISPLAY is touched or

; any line is scrolled upon.

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below1: ljmp main

below2: ljmp label

below3: ljmp transfer

display: mov a, r7

cjne a, #16, display1

mov a, #0c0h ; Forcing the cursor to 1st position of 2nd line.

acall command

acall delay

display1: cjne a, #32, display2 ; Initialise the LCD if the

; 16th position of 2nd line

; has been written.

lcall LCD_init

display2: mov p1, r3 ; Displaying the char.

setb p2.5

clr p2.4

setb p2.3

acall delay

clr p2.3

inc r7

mov r0, 40h

mov a, r3

mov @r0, a

inc 40h

sjmp stay

match2: clr c

subb a, @r0

cjne a, #0, next ; Checking if the lines of the

; character in ROM matches with

; the lines stored in RAM.

inc r6 ; Incrementing for next line in ROM.

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ljmp again2

next: dec r0

djnz r5, again3 ; Decrementing r4 & r5 for previous line

; stored in RAM.

next_char: mov a, r4

add a, #3

mov r4, a

incr: inc dptr ; Incrementing dptr for next character

; stored in ROM.

djnz r4, incr

clr a

movc a, @a+dptr

cjne a, #'!', below4 ; Checking for an invalid

; set of scrolled lines.

ljmp main

below4: ljmp ch_mtch_dsp

LCD_init: mov r7, #0 ; Counter for LCD's cursor position or for

; counting the number of characters that

; have been displayed.

mov 40h, #42h ; Initial RAM address for storing the

; characters to be transferred.

mov 41h, #'!' ; For comparison purpose.

mov a, #38h ; LCD's initialisation.

acall command

acall delay

mov a, #0eh

acall command

acall delay

mov a, #01h

acall command

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acall delay

mov a, #06h

acall command

acall delay

mov a, #80h

acall command

acall delay

ret

command: mov p1, a

clr p2.5

clr p2.4

setb p2.3

acall delay

clr p2.3

ret

delay: mov r0, #10

here2: mov r4, #255


djnz r0, here2

ret

delay1: mov r0, #255

here4: mov r5, #255


djnz r0, here4

ret

delay2: mov r0, #2

here7: mov r3, #255

here6: mov r4, #255

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djnz r3, here6

djnz r0, here7

ret

;---------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------

org 0300h

lines: db 0ffh,0fah,0f6h,0edh,0f9h,0ddh,0f5h,0beh,7eh,7bh,0f3h,0e7h,0ebh,0dbh,0d7h,0b7h,3fh,0

characters: db 'A',8,1,2,3,4,7,8,12,16,0

db 'B',10,1,2,3,4,5,6,7,8,12,16,0

db 'C',6,1,2,5,6,7,8,0

db 'D',7,3,4,5,6,7,12,16,0

db 'E',8,1,2,5,6,7,8,12,16,0

db 'F',6,1,2,7,8,12,16,0

db 'G',8,1,2,4,5,6,7,8,12,0

db 'H',6,3,4,7,8,12,16,0

db 'I',6,1,2,5,6,10,14,0

db 'J',6,1,2,6,7,10,14,0

db 'K',4,10,11,13,14,0

db 'L',4,5,6,7,8,0

db 'M',6,3,4,7,8,9,11,0

db 'N',6,3,4,7,8,9,13,0

db 'O',8,1,2,3,4,5,6,7,8,0

db 'P',7,1,2,3,7,8,12,16,0

db 'Q',9,1,2,3,4,5,6,7,8,13,0

db 'R',8,1,2,3,7,8,12,13,16,0

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db 'S',8,1,2,4,5,6,8,12,16,0

db 'T',4,1,2,10,14,0

db 'U',6,3,4,5,6,7,8,0

db 'V',2,9,11,0

db 'W',6,3,4,7,8,13,15,0

db 'X',4,9,11,13,15,0

db 'Y',3,9,11,14,0

db 'Z',6,1,2,5,6,11,15,0

db '0',6,2,3,4,5,10,14,0

db '1',2,10,14,0

db '2',8,1,2,3,5,6,7,12,16,0

db '3',8,1,2,3,4,5,6,12,16,0

db '4',5,3,4,8,12,16,0

db '5',5,2,4,5,10,12,0

db '6',9,1,2,4,5,6,7,8,12,16,0

db '7',4,1,2,11,15,0

db '8',7,2,3,4,5,10,12,14,0

db '9',7,1,2,3,4,8,12,16,0

db '$',10,1,2,4,5,6,8,10,12,14,16,0

db '*',8,9,10,11,12,13,14,15,16,0

db '+',4,10,12,14,16,0

db '-',2,12,16,0

db '',2,9,15,0

space: db ' ',2,5,6,0

delete: db '/',2,11,15,0

invalid:db '!'

END

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V. References

Books referred:

1) The 8051 Microcontroller and Embedded Systems Using

Assembly and C By Muhammad Ali Mazidi, Janice Gillispie

Mazidi & Ro lin D. McKinlay

Websites referred:

1) Atmel Corp. Makers of the AVR microcontroller

www.atmel.com

2) One of the best sites AVR site www.avrfreaks.net

3) One of the best sites for Microcontroller projects

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www.kmitl.ac.th

4) Keil, the developer of Keilvision www.keil.com

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