AT89C52 Character LCD and Keypad Interfacing Using C

We have seen about 4x4 matrix keypad and character LCD interfacing with AT89C52 in previous post. Now let put these two external devices to work together with this controller.

In this programming example, I use a 4x4 matrix keypad and a HD44780-based character LCD, controlled by AT89C52. The two lines character LCD shows the received the controller received from keypad.

This keypad has 16 value ranging from 1 to 9, and from A to F in ASCII format.

Circuit diagram

Source code is written in C, using Keil uVision IDE.

/*
AT89C52 8051 Interface to Character LCD
and Matrix Keypad Programming in C using Keil
*/
 
#include <REG52.h>
 
#define DPORT				P2
#define KEY_PORT    P1
 
/*Keypad rows setting*/
sbit 	row0=P1^4;
sbit 	row1=P1^5;
sbit	row2=P1^6;
sbit	row3=P1^7;
 
/*
RS bit 0
RW to  GND
EN bit 1
*/
 
void	lcdInit();
void	lcdCmd(unsigned char cmd);
void	lcdDat(unsigned char dat);
void	lcdStr(unsigned char *str);
void	lcdXY(unsigned char x, unsigned char y);
void 	_delay_us(unsigned int t);
void 	_delay_ms(unsigned int T);
void	lcdClear();
 
/**********KeyPad*************/
unsigned char getKey();
 
unsigned char keypad[4][4]={0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
unsigned char	output[4]={0xFE,0xFD,0xFB,0xF7};
unsigned row,col,key_value;
bit    found=0;
 
unsigned char temp;
 
int main(void)
{	
	  unsigned char keyVal,pressCnt=0;
	  unsigned char keyStr[16];
	  unsigned int i=0;
		unsigned char keyChar[16]={'7','8','9','F','4','5','6','E','1','2','3','D','A','0','B','C'};
	  lcdInit();
		KEY_PORT=0xF0;
	  lcdXY(1,1);
	  P3=0x00;
		lcdStr("Enter Key Value:");
		lcdXY(1,2);
    while(1)
    {
			keyVal=getKey();
			if(found==1){
				lcdDat(keyChar[keyVal]);
				found=0;
				pressCnt++;
				for(i=0;i<32800;i++);
			}
			if(pressCnt>16){
				pressCnt=0;
				for(i=0;i<50000;i++);
				lcdClear();
				lcdXY(1,1);
				lcdStr("Enter Key Value:");
				lcdXY(1,2);
			}
    }
 
}
 
 
void lcdCmd(unsigned char cmd){
	temp=0x02;
	DPORT=temp|(cmd&0xF0);
	_delay_us(10);
	temp=0x00;
	DPORT=temp|(cmd&0xF0);
	_delay_us(100);
 
	temp=0x02;
	DPORT=temp|(cmd<<4);
	_delay_us(10);
	temp=0x00;
	DPORT=temp|(cmd<<4);
}
 
void lcdDat(unsigned char dat){
	temp=0x03;
	DPORT=temp|(dat&0xF0);
	_delay_us(10);
	temp=0x01;
	DPORT=temp|(dat&0xF0);
	_delay_us(100);
 
	temp=0x03;
	DPORT=temp|(dat<<4);
	_delay_us(10);
	temp=0x01;
	DPORT=temp|(dat<<4);
}
 
void lcdInit(){
 
	DPORT=0x00;
	_delay_ms(2);
	lcdCmd(0x33);
	_delay_us(100);
	lcdCmd(0x32);
	_delay_us(100);
	/*2-Lines Mode 4-Bit*/
	lcdCmd(0x28);
	_delay_us(100);
	/*Display On Cursor Blink*/
	lcdCmd(0x0F);
	_delay_us(100);
	/*Clear Screen*/
	lcdCmd(0x01);
	_delay_ms(2);
	/*Cursor Increment*/
	lcdCmd(0x06);
	_delay_us(100);
}
 
void lcdStr(unsigned char *str){
	unsigned char i=0;
	while(str[i]!=0){
		lcdDat(str[i]);
		i++;
	}
}
 
void lcdXY(unsigned char x, unsigned char y){
	/*20x4 LCD Address */
	//unsigned char tbe[]={0x80,0xC0,0x94,0xD4};	
	/*16x2 LCD Address*/
	unsigned char tbe[]={0x80,0xC0};
	lcdCmd(tbe[y-1]+x-1);
	_delay_us(100);
}
 
void _delay_us(unsigned int a){
	unsigned int i,j;
	for(i=0;i<5;i++)
		for(j=0;j<a;j++);
}
 
void _delay_ms(unsigned int b){
	unsigned int i;
	for(i=0;i<b;i++)	_delay_us(1000);
}
 
void lcdClear(){
	lcdCmd(0x01);
	_delay_us(10);
}
 
/*4x4 Matrix KeyPad Routine*/
unsigned char getKey(){
 
    static unsigned char i=0;
 
		for (i=0;i<4;i++){
            KEY_PORT=output[i];
            if((KEY_PORT&0xF0)!=0xF0)  
            {   col=i;
                found=1;
                break;
            }
        }
 
        if(row0==0) row=0;
        else if (row1==0)   row=1;
        else if (row2==0)   row=2;
        else if (row3==0)    row=3;
 
        if(found==1)
					return key_value=keypad[row][col];   
				found=0;
}
 

Click here to download source file.