LCD interfacing with 8051

Hello Everyone!!!
Many people face a lot of problems in interfacing LCD with 8051 micro controller, but in reality it is very easy and even fun to interface an LCD!!

16*2 LCD LM0161

WHAT DOES DIFFERENT PINS STAND FOR IN LCD????

First of all we will need to understand what does the pins in the LCD means...

VSS: To be provided with Ground.

VDD: To be provided with Source voltage.

VEE: Can be grounded or a potentiometer can be used to adjust the contrast of LCD.

RS: Is the register select pin decide either to write comment or data

RW: Is the read write pin decide either to write or read data

E: Is the enable pin used as clock

D0-D7 : Are the data pins messages are send on these pins.

There are two things to be written on LCD 

1) Command

2) Data 

What is a Command??? 

A command is a code for LCD that order it to set itself as per our requirements.

for example:

01H will clear your LCD

06H cursor will be incremented by 1 unit

How to write command?

In order to write a command we will need to :

• clear the RS pin (RS=0)
• clear the RW pin (RW=0)
• Give clock on E pin with some delay

CODE:

For clearing LCD:

mov DATA,#01H

clr RS

clr RW

setb E

nop

nop

clr E

this code will clear you LCD many commands are available on internet.

Now What is a Data???

The data is simply the message we want to display on LCD.

How to write Data?

In order to write a data we will need to :

• High the RS pin (RS=1)
• clear the RW pin (RW=0)
• Give clock on E pin with some delay

CODE:

For displaying letter 'A' on LCD:

mov DATA,#'A'
setb RS
clr RW
setb E
nop
nop
clr E

this code will display letter A on the LCD.

WRITING ON LCD!!!

As you are familiar with coding of LCD let us write our topic name on LCD!!!

SCHEMATIC:

CODE:

;---INIITIALIZING PORTS AND BITS----

rs bit P3.0     ; initializing port 3.0 as register select pin

rw bit P3.1      ; initializing port 3.1 as read/write pin

en bit P3.2     ; initializing port 3.2 as enaable pin

dat equ P2     ; initializing port 2 as data bus

org 00h  

jmp 30h

org 30h

;---WRITING COMMANDS ON LCD ----

mov A,#38h     ;Use 2 lines and 5×7 matrix for LCD

acall com_wrt ; calling function to enter command on LCD 

mov A,#0Fh ; LCD ON, Cursor ON, Cursor blinking ON

acall com_wrt ; calling function to enter command on LCD 

mov A,#01h     ; clearing the LCD

acall com_wrt ; calling function to enter command on LCD  

mov A,#80h     ; Force cursor to the beginning of 1st line

acall com_wrt ; calling function to enter command on LCD 

;---CLEARING/SETTING PORTS/PINS----

mov P2,#00H ; clearing port 2 to eleminate garbage value

;---START OF PROGRAM----

START:

call clear ; calling function to clear LCD

DISPLAY_MSG:

mov dptr,#msg ; copy message in data pointer to be displayed on LCD

call dmsg ; calling function to display message on LCD

DISPLAY_MSG1:

call nline

mov dptr,#msg1

call dmsg

jmp exit

clear:  ; LCD clearing module

mov a,#01h          ; clearing LCD 

acall com_wrt  ; calling function to enter command on LCD

ret  ; returning back 

dmsg:

call delay   ; calling some time delay

clr A   

movc a,@a+dptr   ; moves code byte of data located in program code ROM into Accumulator A

call char_wrt   ; calling function to write character 

inc dptr   ; incriment the value of data pointer by 1

jz display_msg1

jmp dmsg

;---CHARACTER DISPLAYING MODULE----

char_wrt:  

acall delay  ; calling some time delay

setb rs  ; setting bit register select high 

clr rw  ; clearing bit to write data on LCD

mov dat,A  ; moving character to data port

setb en  ; setting bit enable for starting clock

nop  ; time delay

nop  ; time delay

clr en  ; clearing bit enable for ending clock

ret      ; return back

;---COMMAND DISPLAYING MODULE----

com_wrt:

acall delay  ; calling some time delay

clr rs  ; rs=0 for writting comment

clr rw  ; rw=0 for writting comment

mov dat,A  ; copying acumulator in data port (p2)

setb en  ; en=1 for clock

nop  ; time delay

nop  ; time delay

clr en  ; en=0 for clock

ret  ; return to previous position

;---DELAY MODULE----

delay:

mov r6,#088h

loop:

djnz r5,$

djnz r6,loop

ret

nline:

mov a,#0c1h  ;next line

call com_wrt   ; calling function write comment on LCD

mov a,#0c0h  ;2nd line 1st position

call com_wrt  ; calling function write comment on LCD

ret

msg: db'LCD INTERFACING ',0

msg1: db' WITH OUR BLOG',0

Exit:

jmp msg1

end