USB Device Interface (UDI) for Device Firmware Upgrade Atmel specific

The DFU from Atmel is based on DFU specification, but does not implement same protocol.

The USB Device Atmel DFU class implement both version:

• The doc7618: USB DFU Bootloader Datasheet describes the FLIP USB DFU Protocol version 1 used by Mega devices.
• The AVR32760: AVR32 UC3 USB DFU Bootloader Protocol and the AVR4023: FLIP USB DFU Protocol describes the FLIP USB DFU Protocol version 2 used by UC3 and Xmega devices.

The interface between the DFU Atmel Class and device is done through the In System Programming API service.

Modules
	Interface with USB Device Core (UDC)
	Structures and functions required by UDC.
	Implementation of UDI DFU Atmel Class
	Class internal implementation.
	USB interface descriptors
	The following structures provide predefined USB interface descriptors.