Portable USB device built with rechargeable functional apparatus

A portable USB device with a rechargeable functional apparatus, comprising:

• a USB connector having +5V, D+, and D− pins for being inserted into a socket of a host device;
• a USB device module powered by the +5V pin and activated to perform data exchange via the D+ and D− pins when the USB connector is coupled to the host device, so as to provide a first specific function to the host device;
• a rechargeable battery;
• a charge circuit for charging the rechargeable battery via the +5V pin when the USB connector is coupled to the host device;
• and
• a functional apparatus powered by the rechargeable battery so as to provide a second specific function different from first specific function when the USB connector is not coupled to the host device,
• wherein the first specific function is an I/O function, and the USB device module provides the I/O function and data storage space, so that, when the USB connector is coupled to the host device, the USB device module is powered via the +5V pin and controlled via the D+ and D− pins to achieve the I/O function and data exchange, and
• wherein the functional apparatus is an illuminating apparatus, and the illuminating apparatus further comprises a push button operable to supply power from the rechargeable battery to the illuminating apparatus.