Select the firmware for your board, most likely one of the following: BoardĪrduino-usbserial-atmega16u2-Mega2560-Rev3.hexĪrduino-usbserial-atmega16u2-MegaADK-Rev3.hexĪrduino-usbserial-atmega16u2-Uno-Rev3.hexĢ. Within the platform directory, the usb to serial firmware is found in firmwares/atmegaxxu2/arduino-usbserial. Alternatively, you can download and extract the repository from the GitHub page (Code > Download ZIP). The platform comes installed with Arduino IDE by default, and can be found in the Arduino15 directory: Arduino15/packages/arduino/hardware/avr/. The firmware is included in the Arduino AVR Boards platform. Note that this article does not apply to the Uno WiFi Rev2, which uses a different chip with closed source firmware. The converter chip firmware can be flashed with a computer by setting the board to DFU mode (Device Firmware Update). The following boards use either an Atmega16U2 or Atmega8U2 chip as a USB-to-serial converter: