I have a Regal with level 5 trim, which means a USB port that I successfully connect my Iphone to in order to listen to music through the Regal system. When I try to use a flash drive full of mp3s, the system doesn't recognize the drive. Does anyone know what the problem is, or whether the level 5 trim system, despite it being rigged for USB, in fact is equipped to play mp3s from a flash drive? This is a CXL not a Turbo, the higher end system but not with navigation.