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This projects allows flashing of Arduino UNO R3 via USB Mass Storage(i.e., file copy or drag and drop without needed to install any software).

It implements it in firmware of the ATmega16u2 - the USB interface chipon the Arduino UNO. This firmware in turn talks to theoptiboot bootloaderrunning on the main ATmega328p chip.

The mass storage interface accepts files inUF2format. The new format (i.e., not.hex and not.bin) is necessary to implementa reliable mass storage flashing in the 512 bytes of RAM of the ATmega. The UF2 repositorycontains some conversion tools, and recent PXT versions havepxt hex2uf2 command.

There's now ablog post up about how itworks and how it came about.

$ git clone https://github.com/abcminiuser/lufa lufa$ cd lufa/Projects$ git clone https://github.com/mmoskal/uf2-uno$ cd uf2-uno$ make

I'm using LUFA170418 right now. You need to haveavr-gcc etc inPATH.I'm using 4.9.

Check outbinary releases.

• place the ATmega in DFU update mode by shorting two pins sticking out closest to the USB plug
• under macOS or Linux installdfu-programer and runmake burn
• under Windows useAtmel FLIP

Arduino providesmore detailed instructions.

Note: this bootloader is not currently compatible with Arduino IDE. If you wantthat, go back to the original bootloader (also following the instructions from the Arduinopage above).

The firmware exposes a custom raw HID interface, implementing a small subset ofHF2 protocol, in particularthe serial-forwarding parts. The serial can be accessed using the C-baseduf2tool or usingPXT command line.

On the Arduino side you have to useSerial.init(115200); insetup(),and not any other baud rate.

MIT

This code is based on the Mass Storage example fromLUFA,has a few lines and the RingBuffer from theArduino USBSERIAL firmware,and lifts some code from theSAMD21 UF2 Bootloader.All these are MIT licensed.