LCD Display with Arduino / ATmega

(Deutsche Version) I bought this LCD module and this I2C controller. In this post, I will explain how to display text on the display. At first, you need the LiquidCrystal_I2C library from here. (I took the newest Version). Now you can directly start in the Arduino development enviroment. At first the includes:

#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>

Next, you have to define several things which are (in the library) not suitable for my LCD module:

#define I2C_ADDR    0x20

#define BACKLIGHT_PIN  3
#define En_pin  2
#define Rw_pin  1
#define Rs_pin  0
#define D4_pin  4
#define D5_pin  5
#define D6_pin  6
#define D7_pin  7

#define  LED_OFF  1
#define  LED_ON  0

Now you have to define the display:

LiquidCrystal_I2C  lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);

Next, you can start in the setup()-function. At first, you have to tell the program what kind of display you have (the size, I have a 20 x 4 character display).

  lcd.begin (20,4);
  lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE);
  lcd.setBacklight(LED_ON);

The rest is needed if you want to switch on the backlight with lcd.backlight();. Afterwards, the display is resetted:

  lcd.clear();
  delay(1000);
  lcd.home();

Now you can write things onto the display:

  lcd.print("Hello, world!");

To place the cursor at a specified position, you have to do the following:

  lcd.setCursor(5,1);

This should cover all basic functions. To delete everything, simply call lcd.clear(); .

A small hint, this problem took some time for me to solve: If you program an ATmega and then plug it into a pin board, usually nothing works, the ATmega needs a reset after it is plugged into the pin board. This could be caused by the fact that the ATmega already starts running when only some pins are connected to the pin board.