In this tutorial let's interface a 16x1,16x2 and 20x4 character display with AVR breakout board. For this tutorial we will require a LCD Breakout.

Basics

LCD can be interfaced with Atmega128 breakout in two modes i.e. 8 bit and 4 bit. Let's interface it in 4 bit mode.We will connect the display in 4 bit mode. You can change it to 8 bit mode making changes in connections and corresponding code. Hardware connections remain same for LCD 16x1,16x2,20x4 as shown in hook up.
Refer 8051 Tutorial for basics of character LCDs

Hook Up

0Interfacing LCDs with Atmega128 Breakout bb.png

Code

LCD 16 x 1

#include "lcd.h"
int main() 
{
    /*Connect RS->PB0, RW->PB1, EN->PB2 and data bus to PORTC.4 to PORTC.7*/
    LCD_SetUp(PB_0,PB_1,PB_2,P_NC,P_NC,P_NC,P_NC,PC_4,PC_5,PC_6,PC_7);
    LCD_Init(1,16); 
    LCD_DisplayString("Explore");
    while(1);
    return (0);
}

LCD 16 x 2

#include "lcd.h"
int main() 
{
    /*Connect RS->PB0, RW->PB1, EN->PB2 and data bus to PORTC.4 to PORTC.7*/
    LCD_SetUp(PB_0,PB_1,PB_2,P_NC,P_NC,P_NC,P_NC,PC_4,PC_5,PC_6,PC_7);
    LCD_Init(2,16);
 
    LCD_DisplayString("Explore Embedded");
    LCD_DisplayString("Lcd 4-bit Mode");
    while(1);
 
    return (0);
}

LCD 20 x 4

#include "lcd.h"
int main() 
{
    /*Connect RS->PB0, RW->PB1, EN->PB2 and data bus to PORTC.4 to PORTC.7*/
    LCD_SetUp(PB_0,PB_1,PB_2,P_NC,P_NC,P_NC,P_NC,PC_4,PC_5,PC_6,PC_7);
    LCD_Init(4,20);
 
    LCD_DisplayString("Explore Embedded\n");
    LCD_DisplayString("LCD 4-bit Mode\n");
    LCD_DisplayString("20 x 4 \n");
    LCD_DisplayString(":)  :O");
 
    while(1);
 
    return (0);
}