Help LCD


I was doing some stuff with the LCD I2C.

When i uploaded the code , the LCD didnt show all the letters.

then i try some uploading some easy code and the LCD failed again.

i used this simple code and the LCD only shows the “H”

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x20,20,4);
void setup() {


void loop() {
lcd.print ("hello world");

does any one knows whats going on?

Yes. You are using an outdated library that has a bug in it. You should update your library to the latest LiquidCrystal_I2C library.

Alternatively, you could use my hd44780 library package. It is faster than that library and has some additional capabilities, like auto detection of the i2c address, pin mappings and backlight active level. It can also read data from the display. It is available in the IDE library manager. You can read more about it here:

The i/o class for pcf8574 based backpacks is hd44780_I2Cexp. After installation, I would recommend that you first run the included diagnostic sketch (I2CexpDiag) to verify that the library and the lcd are properly working.

--- bill