UNO and a QC2004A w/ a backpack

Please help, I'm a newbie. I've bought a QC2004A display already soldered with this backpack click here to see (mine backpack has an original chip from Philips with the same signature as the one in the auction PCF8574t

1)Please help me to wire it with Arduino UNO R3

For now I connected

  • VCC from backpack to V5 or V3.3 on UNO
  • GND to GND
  • SDA from backpack to A4 on UNO
  • SCL from backpack to A5 on UNO

Is this correct?

2)I don't know how let it work via software, I already set contrast at max so I can barely see leds on line 1 and 3 of the display, but don't know how to light up the led behind the screen.. Can some one give me a simple Hello World sketch to try it?


Finally I did it! :D

Hi Tronky,

I've the same problem. How did you fix is?