PIC16F887 KeyPad and Character LCD Example using XC8

A keypad scanning program is common for most of micro-controller programming students. It usually done by the Assembly language programming in a micro-processor class in university. However using C compiler to program the keypad scanning process is very easy, and it's almost readable for most C programmers.

Simulating Program

Using a single 8-bit I/O port can make a 4x4 (16 keys) matrix keypad. It's divided into two nibbles, one nibble for output and another nibble for input data.

Arduino 4x4 Matrix Keypad Module

 

In this example, I use a PIC16F887 micro-controller to scan a 4x4 matrix keypad. Input key will show on a 16x2 character LCD. 

/*
 * File:   main.c
 * Author: Admin
 *
 * Created on January 16, 2024, 7:46 PM
 */
 
#include <xc.h>
#include "config.h"
#include "LCD4Bits.h"
 
#define _XTAL_FREQ  8000000UL
 
uint8_t key_16[][4]={'7','8','9','F',
                     '4','5','6','E',
                     '1','2','3','D',
                     'A','0','B','C'};
 
uint8_t scanKey(void){ 
    char data=0,temp;
    for(uint8_t i=0;i<4;i++){
        PORTB=1<<i;
        data=PORTB&0xF0;
        if(data&(1<<4))     {temp=key_16[i][0]; break;}
        else if(data&(1<<5)){temp=key_16[i][1]; break;}
        else if(data&(1<<6)){temp=key_16[i][2]; break;}
        else if(data&(1<<7)){temp=key_16[i][3]; break;}
        else temp=0;
        __delay_ms(10);
    }
    return temp;
}
 
void main(void) {
    OSCCONbits.IRCF=7;
    uint8_t temp,count=0,row=0;
    PORTB=0;
    TRISB=0xF0;
    ANSELH=0;
    lcdInit();
 
    while(1){
        temp=scanKey();
        if(temp!=0){          
            lcdData(temp);
             count++;
            __delay_ms(250);
        }                  
        if(count>16){count=0; lcdCommand(0xC0); row+=1;}
        if(row>=2) {
            count=0; 
            lcdXY(1,1); 
            lcdCommand(0x01); 
            __delay_ms(10);
            row=0;
        }
    }
    return;
}
 

After a 16 key-press count, a new line will start. After two lines, the display will clear, and it will return home.

Click here to download this example from GitHub. See also,

• ATMega32 interfaces to keypad and display
• ATMega32 LCD and Keypad Interfacing Example