8051 LCD interfacing for sending string
8051 LCD interfacing, sometimes becomes difficult in assembly. Unless and you give it a try your self you wont be able to do it. Following is the code for 8051 lcd interfacing experimentally tested on lcd and verified in all respects. So there is no doubt about the working of this code. This is not a hi-fi code but this code is sufficient for the beginners working with 8051 lcd interfacing.
;OBJECTIVE:
;THIS PROGRAM DISPLAYS THE STRING "TEMPERATURE" ON LCD AND CONVERT HEX NUMBER(WHICH IS WRITTEN '1EH' IN THE
;PROGRAM) IN DECIMAL.HEX NUMBERS HAVE RANGE(0AH-64H) BECAUSE THIS PROGRAM IS ABLE TO SHOW DECIMAL NUMBER
;FROM (10-100)
;PROGRAMER: JAMAL
;University : NUST
;PROGRAM NAME: LCD DISPLAY HEX TO DECIMAL CONVERSION
;MICROCONTROLLER: ATMEL AT89S52
;**************************************************************************************
;........DEFINING VARIABLES..........
ORG 00H
RS_LCD BIT P1.5 ; pins 1.5,1.6,1.7 of microcontroller
RW_LCD BIT P1.6 ; is connected with register select,
EN_LCD BIT P1.7 ; write and enable pin of lcd
OUTPUT_LCD EQU P3 ; port3 is connected with data pins of
OUTPUT_ADC EQU P2 ; lcd
STR_PTR EQU 35H ; STR_PTR is a memory location
;**************************************************************************************
;................MAIN PROGRAM.......................
CLR EN_LCD ; make en=0
CALL SEND_STRING ; call subroutine
CALL SEND_HEX_TO_DEC
HERE: SJMP HERE
;**************************************************************************************
;.........ROUTINE FOR DISPLAYING STRING..............
SEND_STRING: CALL INIT_LCD
MOV OUTPUT_LCD,#01h ; clear lcd screen
CALL WR_LCD_COMMAND
CALL WAIT_LCD
MOV OUTPUT_LCD,#80H ; address for the first line of lcd
CALL WR_LCD_COMMAND ; call routines to initalize lcd
CALL WAIT_LCD ; call routine to check busy flag
MOV DPTR,#STRING ; move 16 bit string to data pointer
MOV STR_PTR,#0FFH ; make str_ptr an input
STRING_ROUTINE: INC STR_PTR
MOV A,STR_PTR
MOVC A,@A+DPTR ; move string to A
CJNE A,#'$',STRING_ROUTINE ; check the condition
JMP EXIT_LCD_MSG
DISP_AGN: MOV OUTPUT_LCD,A ; move data of A to lcd
SETB RS_LCD ; make rs=1
CLR RW_LCD ; make rw=0
SETB EN_LCD ; apply high to low pulse for writing data
CLR EN_LCD
CALL WAIT_LCD
JMP STRING_ROUTINE
EXIT_LCD_MSG:
RET
;**************************************************************************************
;..........ROUTINE TO CONVERT HEXADECIMAL NUMBER TO DECIMAL NUMBER...........
SEND_HEX_TO_DEC:CALL INIT_LCD
MOV OUTPUT_ADC,#0FFH ; make port2 an input port
MOV A,#1EH ;'1EH 'can be any number which we want to convert into
; decimal(10-100) for display on lcd
CJNE A,#01100100B,CONVERSION ; jump occurs if A is not equal to 100
MOV B,#10 ; move 10 in B
DIV AB ; process to convert hexadecimal number
MOV R7,B ; into decimal number by dividing by 10
MOV B,#10 ; store the result in registers
DIV AB
MOV R6,B
MOV R5,A
CALL DISPLAY
BACK:
RET
CONVERSION: MOV B,#10
DIV AB
ADD A,#30H
CALL WR_LCD_DATA ; call subroutine to send data to lcd
MOV A,B
ADD A,#30H ; subtract 30H from A to convert from ascii
CALL WR_LCD_DATA ; character
JMP BACK
DISPLAY: MOV A,R5 ; most significant digit
ADD A,#30H
CALL WR_LCD_DATA
mov A,R6
ADD A,#30H
CALL WR_LCD_DATA
mov A,R7 ; least significant digit
ADD A,#30H
CALL WR_LCD_DATA
RET
;**************************************************************************************
;...........ROUTINE FOR INITALIZATION OF LCD.............
INIT_LCD: MOV R0,#04H ; loop to initalize to lines of lcd
MOV OUTPUT_LCD,#38H ; by sending 38H
AGAIN: CALL WR_LCD_COMMAND
DJNZ R0,AGAIN
CALL WAIT_LCD
MOV OUTPUT_LCD,#0Eh ; display on,cursor on
CALL WR_LCD_COMMAND
CALL WAIT_LCD
RET
;**************************************************************************************
;.......... ROUTINE FOR SENDING COMMANDS TO LCD.............
WR_LCD_COMMAND: CLR RS_LCD ; commands are sent by making rs=0,
CLR RW_LCD ; rw=0, and high to low pulse on
SETB EN_LCD ; enable pin
CLR EN_LCD
RET
;**************************************************************************************
;..........ROUTINE FOR SENDING DATA TO LCD..................
WR_LCD_DATA: MOV OUTPUT_LCD,A
SETB RS_LCD ; commands are sent by making rs=1,
CLR RW_LCD ; rw=0, and high to low pulse on
SETB EN_LCD ; enable pin
CLR EN_LCD
CALL WAIT_LCD
RET
;**************************************************************************************
;..........ROUTINE FOR CHECKING BUSY FLAG OF LCD.............
WAIT_LCD: MOV OUTPUT_LCD,#0FFH ; make port 3 an input port
CLR EN_LCD
CLR RS_LCD
SETB RW_LCD
SETB EN_LCD
MOV A,OUTPUT_LCD
JB ACC.7,WAIT_LCD
CLR EN_LCD ; clear the enable for other commands
ret
;*************************************************************************************
;........... STRING TO BE DISPALYED ON LCD.....................
ORG 100H
STRING: DB 'TEMPERATURE=$' ; string end with a null character
; $ sign shows end of string
;*************************************************************************************
END ; end of program
