I am trying to initialize a 4x20 LCD using a PIC18 in 8bit serial interface. This is an LCD I found lying around in the lab and I cant find a datasheet for this exact one.

I am struggling to get it to work as all I ever achieve are blocks on the LCD. I have spent countless hours with no sign of success. Is there something in the code that I am missing?

All help is appreciated.


#define DataBus PORTA      //Data is set to 8 pins on port A
#define RS PORTCbits.RC0   
#define RW PORTCbits.RC1 
#define Enable PORTCbits.RC2 

void LCD_CmdWrite(int Cmd){
DataBus = Cmd;   //Sets command on Port A pins
Enable = 0;
RS = 0;
RW = 0;
Enable = 1;
__delay_ms(20);  //Delay for LCD
Enable = 0;



void LCD_intialize(){
RW = 0;

LCD_CmdWrite(0x38);  //LCD 8 bit mode
LCD_CmdWrite(0x01);  //Clears LCD
LCD_CmdWrite(0x0F);  //Display on, cursor on, blink on



#include <xc.h>  //Allows access to device specific features like TRIS etc.
#include <stdio.h>  //Allows access to input/output pins
#include <stdlib.h>  //Memory management and text conversion

#include "LCD.h" //Includes LCD Display functions

void main(void) {
OSCEN = 0b01000000;
OSCCON1 = 0b01100000;  
OSCCON2 = 0b01100000;
OSCFRQ = 0b000101;   //Sets clock at 16MHZ

TRISC = 0x00; //Sets PORT C as Output
TRISA = 0x00;//Sets PORT A as Output
PORTC = 0;
PORTA = 0;

LCD_intialize();  //Initializes LCD

LCD_clear();  //Clears LCD again


  • \$\begingroup\$ "This is an LCD I found lying around in the lab and I cant find a datasheet for this exact one. " So... yeah. \$\endgroup\$ – Harry Svensson Jul 30 '17 at 8:54
  • \$\begingroup\$ Which PIC18 MCU? \$\endgroup\$ – Bruce Abbott Jul 31 '17 at 5:39

Figure out what the LCD is. One way to do it is to power it up without initialization and adjust the contrast to see if you see a line of black boxes in the top row. If you do, it is the good old 44780. Find a data sheet and code to it.

If not, well, it will be a lot harder. But focus on finding a data sheet.

  • \$\begingroup\$ I get two bars, one the 1st and 3rd row. Does that means its a 44780? thank you for you reply! \$\endgroup\$ – DigiJockforLife Jul 30 '17 at 18:03

If the LCD is a 44780 then you could be Lucky. A company with the name of Extreme Electronics (India) produced a downloadable library complete with setup etc. I myself used the lib for pic1618877,pic16F648A and pic16F877A. The lib is small and can be adapted to your personal needs. For the pic16F18877 I needed to modify the use of the registers.

Here is the link http://extremeelectronics.co.in/pic16f877a-tutorials/setup-and-use-of-lcd-library-for-pic/

Looking at the comment it looks like a 44780. The described error can happen after a programming and restart cycle.. In that case power off and restart.


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