I have a Due and the following LCD: http://www.sainsmart.com/arduino/arduino-shields/lcd-shields/sainsmart-iic-i2c-twi-serial-2004-20x4-lcd-module-shield-for-arduino-uno-mega-r3.html
I have tried to follow the instructions there, and tried several versions of the LiquidCrystal_I2C library with no luck (except making the backlight flash, can't get any text to print). I used the I2C scanner sketch to find the I2C address (0x27, not 0x3F as specified on the product page).
Last thing I tried was the example sketch that came with V2 of the LiquidCrystal_I2C library, modified for this LCD:
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,20,4); // set the LCD address to 0x20 for a 16 chars and 2 line display
void setup()
{
lcd.init(); // initialize the lcd
// Print a message to the LCD.
lcd.backlight();
lcd.print("Hello, world!");
}
void loop()
{
}
I have 5V to VCC, GND to GND, SDA to SDA, and SCL to SCL between the Due and the small interface board on the back of the LCD module. I read that the 3.3V levels should work fine with this LCD module, is this not the case? Any ideas?