Unfortunately, this is the case concerning the USB-A ports of most receivers. They require an actual storage device supporting FAT 16/32. Connecting my iPhone to the USB-A ports of my receiver is good for nothing but charging the iPhone. If I want a wired connection from my iPhone to the receiver to play music stored in it or stream from services, it's going to be via an adapter to one of the receiver's analog, digital or HDMI ports.As was mentioned by @BoredSysAdmin, there are some units equipped with USB-B ports that can receive audio signals from connected devices rather than just read files from storage devices like the USB-A ports.