Peter's keyboard firmware (QMK)
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USB to USB keyboard protocol converter

A small device to connect between your USB keyboard and your PC that makes (almost) every keyboard fully programmable. Original code from the TMK firmware. Ported to QMK by Balz Guenat.

Keyboard Maintainer: Balz Guenat Hardware Supported: Hasu’s USB-USB converter, Pro Micro + USB Host Shield, maybe more Hardware Availability: GH thread, self-built

Make example for this keyboard (after setting up your build environment):

make converter/usb_usb:default

See build environment setup then the make instructions for more information.

Troubleshooting & Known Issues

The Pro Micro variant runs at 8MHz, hence the following line in usb_usb/ F_CPU ?= 8000000 If the firmware doesn’t work, try changing that line to F_CPU ?= 16000000 or override the F_CPU variable in the of your keymap.

Getting the Hardware

There are two options to get a converter: You can buy one from Hasu or build one yourself.

Buy a Converter

You can buy a fully assembled converter from me here:

Build one yourself using Arduino Leonardo + Circuit@Home USB Host Shield 2.0

Buying Arduino Leonardo and USB Host Shield 2.0(from Circuit@home) 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 guide


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.


Hasu’s main thread for the converter

Build guide for the Pro Micro variant

Original TMK version of the converter

USB Host Shield 2.0

USB Host Shield 2.0 source

Arduino USB Host Shield (with bootst converter)

Arduino source

Initial release of TMK USB-USB converter

Arduino-based hardware keyboard remapper - Colemak forum

Teensy + Host Shield