This is the DFU firmware for the ATmega16U2 on the Arduino Uno R3 and Arduino Mega 2560, made from scratch using Atmel Studio 7 and its LUFA extension. You'll need an SPI programmer to flash it.
mcuee/arduino-usb-dfu
This is the DFU firmware for the ATmega16U2 on the Arduino Uno R3 and Arduino Mega 2560
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