Connect Yamaha P-105 keyboard to ipad 2 garageband

I have a Yamaha P-105 piano keyboad. It's said to be an "iPad friendly" keyboard. I have the Camera Connection kit along with a AB USB cable. Everything fits, it's all plugged in correctly. But nothing happens. The sound of garageband still goes through the ipad and my piano still sounds like a piano. haha Do I need to get an Midi-USB cable? I don't see why the normal AB USB cable and the camera connection kit will not work. Thanks guys.