The present invention describes a multi-module USB system consisting of a multi-function USB apparatus and associated USB cap. The multi-function USB apparatus operates as a USB host as well as a USB client. The USB cap houses a rechargeable battery pack and when docked with the multi-function USB apparatus provides power to the multi-function USB apparatus. The multi-function USB apparatus and USB cap can also operate independently. The USB system is a multi-functional device having modes that embody, including recording, sharing, playback, storage, and charging battery of USB based portable media devices. Further, the USB system configures itself automatically for the various modes based on use of its interfaces with no specific settings required from the user.