Keyboard firmwares for Atmel AVR and Cortex-M
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USB to USB keyboard protocol converter
See for detail and discussion.

Hardware requirement
There are two options.

### TMK USB-USB Converter
You can buy a fully assembled converter from me here.

### Arduino Leonardo + [email protected] USB Host Shield 2.0
Buying Arduino Leonardo and USB Host Shield 2.0(from [email protected]) will be better, you won't need even soldering iron.

Other compatible boards like Arduino's Shield will also work well but I think Sparkfun's needs to be modified.

Also Pro Micro 3.3V(not Mini) or Teensy with mini host shield will work with some fixes on signal/power routing.

Build firmware

$ git clone git://
$ cd tmk_keyboard
$ git submodule init
$ git submodule update
$ cd converter/usb_usb
$ make

And Program converter. Push button on TMK converter and just run this.

$ make dfu

In case of Leonardo push reset button then run command. Serial port name(COM17) depends your system. On Linux I got /dev/ttyACM0.

$ DEV=COM17 make program
$ avrdude -patmega32u4 -cavr109 -b57600 -Uflash:w:usb_usb.hex -PCOM17

Only supports 'HID Boot protocol'.

Note that the converter can host only USB "boot protocol" keyboard(6KRO), not NKRO, it is possible to support NKRO keyboard but you will need to write HID report parser for that. Every NKRO keyboard can have different HID report and it is difficult to support all kind of NKRO keyboards in the market.

Keymap editor
You can editor keymap and download firmware with web brwoser.


2014/12/11 Added Hub support(confirmed with HHKB pro2)
2016/09/10 Unimap editor support
2016/10/18 Fix LED state at startup

USB Host Sheild 2.0
USB Host Sheild 2.0 source
Arduino USB Host Shield(with bootst converter)
Arduino source{cores,variants}
Initial release of TMK USB-USB converter
Arduino-based hardware keyboard remapper - Colemak forum
Teensy + Host Shield