Melzi/Sanguino ATMEGA 1284P 16Mhz I2C LCD 20x4

Does anyone ever made a I2C LCD 20x4 successfully work on Melzi or Sanguino with ATMEGA 1284P 16MHz?

I connected mine on the pins SDA/SCL/+5V/GROUND of the Melzi board but I can't make it work. It turns on when powered, of course, but does not display anything.

I believe that I'm using the wrong I2C address. I've tried a lot of different addresses without success.

That same LCD display works perfectly using the address 0x27 on an Arduino UNO R3 board. This is the code I'm using to test it:

//I2C LCD Test

#include  
#include 

LiquidCrystal_I2C lcd(0x27,20,4);  // set the LCD address to 0x27 and a 20 chars and 4 line display

void setup()
{
  lcd.init();                      // initialize the lcd 
  // Print a message to the LCD.
  lcd.backlight();
  lcd.setCursor(3,0);
  lcd.print("Hello, world!");
}
void loop()
{
}

Anyone knows the I2C address of the Melzi? Am I connecting to the right pins?

I attached some pictures of the Melzi 1284p with the wired LCD. Please take a look.

Thank you,

Richard