electroSome

Custom Characters on LCD using PIC – MPLAB XC8

Ligo George

I hope that you already go through our tutorial, Interfacing LCD with PIC Microcontroller – MPLAB XC8. HD44780 compatible controllers used in these LCDs allows us to define 8 custom characters in addition to the standard pre-programmed characters. In this tutorial we will learn, how to create custom characters on LCD using PIC Microcontroller and MPLAB XC8 compiler.

DDRAM, CGROM and CGRAM

CGROM – Character Generator ROM

This is the memory which holds 5×8 or 5×10 dot patterns of predefined characters in the LCD. It can generate 208 5×8 dot character patterns and 32 5×10 dot character patterns.

DDRAM – Display Data RAM

This is the memory which holds the character data which is currently displayed on the LCD screen. Its capacity is 80×8 bits, ie 80 characters.

CGRAM – Character Generator RAM

This memory works similar to CGROM but as this is a RAM we can modify its data any time. So we can store our custom character patterns in this memory through program. We can store up to eight 5×8 character dot patterns or four 5×10 character dot patterns in this memory.

Character Generation

Characters are displayed on the LCD using 5×8 or 5×10 dot matrix. Most of the commonly available displays uses 5×8 dot matrix. We can simply create a custom character by defining each pixel in the dot matrix. Here is an example of creating Ω symbol on 5×8 dot matrix.

LCD Custom Character Generation

MPLAB XC8 Code

Note that the following program uses our MPLAB XC8 LCD Library and you should include the header file “lcd.h” to your project directory.

#define _XTAL_FREQ 8000000

#define RS RD2
#define EN RD3
#define D4 RD4
#define D5 RD5
#define D6 RD6
#define D7 RD7

#include <xc.h>
#include <stdio.h>
#include "lcd.h";

// BEGIN CONFIG
#pragma config FOSC = HS   // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF  // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON  // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF   // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF   // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF   // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF    // Flash Program Memory Code Protection bit (Code protection off)
//END CONFIG

const unsigned short MyChar5x8[] = {
  0x00, 0x00, 0x0A, 0x1F, 0x1F, 0x0E, 0x04, 0x00, // Code for char num #0
  0x0E, 0x1B, 0x11, 0x11, 0x11, 0x11, 0x1F, 0x00, // Code for char num #1
  0x0E, 0x1B, 0x11, 0x11, 0x11, 0x1F, 0x1F, 0x00, // Code for char num #2
  0x0E, 0x1B, 0x11, 0x11, 0x1F, 0x1F, 0x1F, 0x00, // Code for char num #3
  0x0E, 0x1B, 0x11, 0x1F, 0x1F, 0x1F, 0x1F, 0x00, // Code for char num #4
  0x0E, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F, 0x00, // Code for char num #5
  0x00, 0x04, 0x02, 0x1F, 0x02, 0x04, 0x00, 0x00, // Code for char num #6
  0x00, 0x00, 0x0E, 0x11, 0x11, 0x0A, 0x1B, 0x00  // Code for char num #7
};
void InitCustomChars()
{
  char i;
  Lcd_Cmd(0x04);   // Set CGRAM Address
  Lcd_Cmd(0x00);   // .. set CGRAM Address
  for (i = 0; i <= 63 ; i++)
    Lcd_Write_Char(MyChar5x8[i]);
  Lcd_Cmd(0);      // Return to Home
  Lcd_Cmd(2);      // .. return to Home
}

int main()
{
  TRISD = 0x00;        // PORTD as Output
  Lcd_Init();
  InitCustomChars();   // Write custom characters to LCD memory
  while(1)
  {
    Lcd_Clear();
    Lcd_Set_Cursor(1,1);
    Lcd_Write_Char(0); // Display Custom Character 0
    Lcd_Write_Char(1); // Display Custom Character 1
    Lcd_Write_Char(2); // Display Custom Character 2
    Lcd_Write_Char(3); // Display Custom Character 3
    Lcd_Write_Char(4); // Display Custom Character 4
    Lcd_Write_Char(5); // Display Custom Character 5
    Lcd_Write_Char(6); // Display Custom Character 6
    Lcd_Write_Char(7); // Display Custom Character 7
    __delay_ms(1000);
  }
  return 0;
}

Hope you can understand the working of the program from above comments. Please comment below if you have any doubts.

Circuit Diagram

Interfacing LCD with PIC Microcontroller – Circuit Diagram

Output

LCD Custom Characters

Download Here