PIC16F84A And Simple Character LCD Interfacing In 8-Bit Mode Using MPLABX XC8

The HD44780-base character LCD is easy to interface with. Electronic technician can test it manually using a simple logic circuit, digital IC circuit, or even using a small micro-controller. Using a micro-controller to interface with this LCD module is very straight forward. The controller only need its 8-bit data port, a Register Select (RS) pin, and Enable (E) pin for the LCD module. The LCD module just need to receive data. So its Read or Write (R/W) is connects to logic 0 or GND. For more information of using this character LCD module using the 8-bit interfacing mode, please see this post.

Program Simulation In Proteus #A

Program Simulation In Proteus #B

 

In this example, I use a simple 8-bit micro-controller, PIC16F84A to interface with this LCD module. It has two general-purpose I/O ports, Port A and Port B. Its total I/O is 11. Port B connects to the 8-bit LCD data bus, while Port A RA0 and RA1 connects to LCD RS and E respectively. The LCD E pin connects to GND as it just need to accept input data or command.

A 16x2 Character LCD Module

Example 1

I wrote this program using MPLABX IDE and v1.51 and XC8 v2.36 (free version). It's very light-weight and simple to use. Using the Assembly language could be effective in built firmware but it could require more lines of written codes.

#include <xc.h>
 
#define _XTAL_FREQ 4000000UL
 
#define RS  RA0
#define EN  RA1
 
#define CLEAR_SCREEN 0x01
 
void lcdCommand(uint8_t cmd){
    PORTB=cmd;
    RS=0;
    EN=1;
    __delay_us(10);
    EN=0;
    __delay_ms(1);
}
 
void lcdData(uint8_t dat){
    PORTB=dat;
    RS=1;
    EN=1;
    __delay_us(10);
    EN=0;
    __delay_ms(1);
}
 
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(0x38);
    lcdCommand(0x0F);
    lcdCommand(0x01);
    __delay_ms(1);
    lcdCommand(0x06);
}
 
int main(void){
    PORTA=0;
    TRISA=0;
    PORTB=0;
    TRISB=0;
    lcdInit();
    __delay_ms(1000);
    lcdXY(3,1);
    lcdString("Hello World!");
    lcdXY(4,2);
    lcdString("PIC16F84A");
 
    __delay_ms(1500);
    lcdCommand(CLEAR_SCREEN);
    lcdXY(1,1);
    lcdString("Programming With");
    lcdXY(1,2);
    lcdString("MPLABX XC8 v2.36");
 
    while(1){
 
    }
    return 0;
}
 

This simple program need almost a quarter of ROM and RAM of the target PIC16F84A chip.

Memory Resource Usage Of PIC16F84

Click here to download its source file

Example 2

Now let make a library for this 8-bit LCD. It requires a pair of a *.h and a *.c file. We need to include these files in project folder before we can call its functions.

Library Test

We can test this library as below.

 
#include <xc.h>
 
#define _XTAL_FREQ 4000000UL
 
#include "LCD8Bits.h"
 
int main(void){
    PORTA=0;
    TRISA=0;
    PORTB=0;
    TRISB=0;
    lcdInit();
    __delay_ms(1000);
    lcdXY(3,1);
    lcdString("Hello World!");
    lcdXY(4,2);
    lcdString("PIC16F84A");
 
    __delay_ms(1500);
    lcdCommand(CLEAR_SCREEN);
    lcdXY(1,1);
    lcdString("Programming With MPLABX XC8 v2.36");
    lcdXY(1,2);
    lcdString("16x2 HD44780 Character LCD Example");
    __delay_ms(1500);
    lcdCommand(0x80);
    for(uint8_t i=0;i<34;i++){
        lcdCommand(MOVE_LEFT);
        __delay_ms(500);
    }
    while(1){}
    return 0;
}
 
 

Sample #1

Sample #2

 Click here to download its source file.