#Microcontrollers LCD interfacing with 8051

// In Embedded C:

/* Connect LCD module to CN2
DATA -> Port0
RS -> P3.2
EN -> P3.3
*/

#include <reg51.h>

#define DATAPORT P0
#define EN 1<<3 // 0000 1000
#define RS 1<<2 // 0000 0100

void delay(void)
{
unsigned int i;
for(i=0;i<0xFF;i++);
}

void LCDcmd(unsigned char cmd)
{
DATAPORT = cmd;
P3 = 0;
delay();
P3 = EN; // P3 = 0000 1000
delay();
P3 = 0;
delay();
}

void LCDdata(unsigned char dat)
{
DATAPORT = dat;
P3 = RS;
delay();
P3 = RS | EN; //P3 = ( 0000 1000 OR 0000 0100) = 0000 1100
delay();
P3 = RS;
delay();
}


void LCD_string(int row, int pos, char *ptr)
{
unsigned char temp;
if(row ==1)
temp = (0x80 | pos);
else
temp = (0xC0 | pos);
LCDcmd(temp); // cursor is set to (row, pos)

while(*ptr)
{
LCDdata(*ptr);
ptr++;
}
}


int main()
{
LCDcmd(0x38); //8 bit
LCDcmd(0x06); //entry mode
LCDcmd(0x0C); // display on cursor off
LCDcmd(0x80); // cursor on 1st line 1st pos
LCDcmd(0x01); // clear display

LCD_string(1,1,"MicroEmbedded");
LCD_string(2,0,"Micro51 S Board");

while(1); //stop here
return 0;

}

// In Assembly

/*------------------LCD---------------------*/

/*

Interfacing Pins : 

P0.0 thru P0.7 interfaced to D0 thru D7.

P3.2 ----> LCD_RS (Register Select).

P3.3 ----> LCD_EN (Enable).

=============================================================================

*/

;Interface declaration

RS  EQU P3^2

EN  EQU P3^3

org 0h

ljmp start

DelaymS:

mov r4,#04 ;  (4*255) ~ 1000uS = 1mS

mov r5,#0

loop:

djnz r5,loop

djnz r4,loop

ret

;Subroutine to write DATA to LCD : 

;Input Value: passed in A accumulator

write_lcd_data:

mov P0,A ;Write the value on port P0

mov r6,#05h ;Call delay for 5mS

continue1:

lcall DelaymS

djnz r6, continue1

SETB RS

SETB EN

mov r6,#01h ;Call delay for 1mS

continue2:

lcall DelaymS

djnz r6, continue2

MOV P3,#00 ; clear the control signals

ret

;Subroutine to send command to LCD

write_lcd_cmd:

mov P0,A ;Write the value on port P0

mov r6,#0ah ;Call delay for 5mS

continue3:

lcall DelaymS

djnz r6, continue3

SETB EN

mov r6,#01h ;Call delay for 1mS

continue4:

lcall DelaymS

djnz r6, continue4

MOV P3,#00 ; clear the control signals

ret

;Subroutine to blink display

blink_display:

mov a,#08

lcall write_lcd_cmd

mov a, #0fh

lcall write_lcd_cmd

ret

start:

mov a,#0x38 ; //function set

lcall write_lcd_cmd

mov a,#0x38 ; //function set

lcall write_lcd_cmd

mov a,#0x08 ; //display off

lcall write_lcd_cmd

mov a,#0x01 ; //display clear

lcall write_lcd_cmd

mov a,#0x06 ; //entry mode set

lcall write_lcd_cmd

mov a,#0x0f ; //display on

lcall write_lcd_cmd

mov a,#0x80 ; //set address counter value

lcall write_lcd_cmd

;Start displaying the string

mov a,#'H'  

lcall write_lcd_data

mov a,#'E'  

lcall write_lcd_data

mov a,#'L'  

lcall write_lcd_data

mov a,#'L'  

lcall write_lcd_data

mov a,#'O'  

lcall write_lcd_data

mov a,#' '  

lcall write_lcd_data

mov a,#'W'  

lcall write_lcd_data

mov a,#'O'  

lcall write_lcd_data

mov a,#'R'  

lcall write_lcd_data

mov a,#'L'  

lcall write_lcd_data

mov a,#'D'  

lcall write_lcd_data

infinite_loop:

// lcall blink_display

sjmp infinite_loop

END