returns TRUE if device has been enumerated (configured) by host, FALSE if it has not. Do not try to use the USB peripheral until you are enumerated.
usb_wait_for_enumeration() - Sits in an infinte loop until device
//// is enumerated. ////
//// ////
//// usb_kbhit() - Returns true if OUT endpoint contains data from ////
//// host. ////
//// ////
usb_task() - Keeps track of connection sense, calling ////
//// usb_detach() and usb_attach() when needed.
//// usb_puts() - Sends a multiple packet message to the host ////
//// ////
//// usb_gets() - Gets multiple packets from the host