I've been driving the wife's car recently, and her head unit is an Alpine CDA-100. It has a USB connector, which my head unit doesn't, so I thought I'd go ahead and hookup my phone (Android) and blast some tunes.
When I connect the phone via USB, the phone starts charging, so some kind of connection got made. However, the head unit displays "USB Err 1." A quick Google search suggests that the USB port is only for thumb drives, not to play music from your phone. Is that so? The music is stored on the SD card, if that matters.