PIC16F84A And Simple Character LCD Interfacing In 4-Bit Mode Using MPLABX XC8

In previous post, I showed about LCD interfacing with PIC16F84A using an 8-bit data mode. For ease of use, most most electronic hobbyists use a 4-bit data mode. It uses only four upper bits D4...7 of the LCD module. The command or data is still 8-bit wide. So the micro-controller needs to send command or data twice. The upper nibble will be transfer first and then the lower nibble.

Simulating Program

 

A low 16x2 cost LCD module (TOP)

A low 16x2 cost LCD module (BOTTOM)

Example 1

In this example I use Port B to interface with this LCD module. Because of PIC micro-controller has a bit addressable instruction, hence we can use a single port interfacing easily. The IDE is MPLABX IDE v1.51 with the XC8 v2.36 compiler.

/*
 * Character LCD Interfacing Using 4-Bit Mode
 * Programming WIth MPLABX XC8
 */
 
#include <xc.h>
 
// PIC16F84A Configuration Bit Settings
 
// CONFIG
#pragma config FOSC = XT        // Oscillator Selection bits (XT oscillator)
#pragma config WDTE = OFF       // Watchdog Timer (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (Power-up Timer is disabled)
#pragma config CP = OFF         // Code Protection bit (Code protection disabled)
 
 
#define _XTAL_FREQ 4000000UL
 
#define RS      RB0
#define EN      RB1
#define DATA8   PORTB
 
void lcdCommand(uint8_t cmd){   
    DATA8=cmd&0xF0;
    RS=0;
    EN=1;
    __delay_us(10);
    EN=0;
    __delay_us(10);
 
    DATA8=cmd<<4;
    RS=0;
    EN=1;
    __delay_us(10);
    EN=0;
    __delay_us(10);
 
    __delay_us(100);
}
 
void lcdData(uint8_t dat){
    DATA8=dat&0xF0;
    RS=1;
    EN=1;
    __delay_us(10);
    EN=0;
    __delay_us(10);
 
    DATA8=dat<<4;
    RS=1;
    EN=1;
    __delay_us(10);
    EN=0;
    __delay_us(10);
 
    __delay_us(100);
}
 
void lcdXY(uint8_t x,uint8_t y){
    /*16x2 Character LCD*/
    uint8_t addr[]={0x80,0xC0};
    lcdCommand(addr[y-1]+x-1);
}
 
void lcdString(uint8_t *str){
    while(*str) lcdData(*str++);
}
 
void lcdInit(void){
    EN=0;
    __delay_us(100);
    lcdCommand(0x33);
    __delay_us(1);
    lcdCommand(0x32);
    __delay_us(1);
    lcdCommand(0x28);
    __delay_us(1);
    lcdCommand(0x0F);
    __delay_us(1);
    lcdCommand(0x01);
    __delay_ms(5);
    lcdCommand(0x06);
}
 
int main(void){
    PORTB=0;
    TRISB=0;
    lcdInit();
    lcdXY(3,1);
    lcdString("Hello World!");
    __delay_ms(1500);
    lcdXY(2,2);
    lcdString("PIC16F84A LCD");
    while(1);
    return 0;
}

Click here to download its source file.

Example 2 - Making A Library Function

For convenient we can make a library function for this LCD controller. We need to make a *.h and a *.c file that will include in project as shown in the example below.

 
#include <xc.h>
 
#define _XTAL_FREQ 4000000UL
 
#include "LCD4Bits.h"
 
int main(void){
 
    PORTB=0;
    TRISB=0;
    lcdInit();
    __delay_ms(1000);
    lcdXY(3,1);
    lcdString("Hello World!");
    lcdXY(4,2);
    lcdString("PIC16F84A");
    __delay_ms(1500);
    lcdCommand(0x0C);
    lcdCommand(CLEAR_SCREEN);
    __delay_ms(500);
    lcdString("Programming With MPLABX XC8 v2.36");
    lcdXY(1,2);
   lcdString("16x2 HD44780 Character LCD Module");
    __delay_ms(1000);
 
    for(uint8_t i=0;i<34;i++){
        __delay_ms(500);
        lcdCommand(MOVE_LEFT);
    }
 
    lcdCommand(CLEAR_SCREEN);
    __delay_ms(500);
    lcdXY(3,1);
    lcdString("AKI-Technical");
    lcdXY(6,2);
    lcdString("BLOGGER");
 
    for(uint8_t i=0;i<16;i++) lcdCommand(MOVE_LEFT);
     for(uint8_t i=0;i<16;i++){
        __delay_ms(500);
        lcdCommand(MOVE_RIGHT);
    }
 
    while(1){}
    return 0;
}

This example scrolls the display left and right.

MPLABX IDE

Simulating Program #1

Simulating Program #2

Click here to download its source file.