https://www.youtube.com/watch?v=FPBzOaLbWhM
There's an even smaller design on the github that I had custom-manufactured at PCBWay before. Please email espusb@gmail if you want to know more.
https://github.com/cnlohr/espusb/tree/master/hardware/usb_82...
Charles Lohr made the amazing design. I built a little on top, and made a slight modification to the firmware to allow text entry in all languages by sending Unicode codepoints.
So now I can type Chinese (or Japanese, Korean, Russian, Arabic, Thai...) on my phone's keyboard, and have the EspUSB type it into my laptop. Very convenient when the characters aren't printed on the keys.
Pity I never figured out how to do the regulatory compliance for the EspUSB, so couldn't follow through on actually getting it onto a web store (e.g. Tindie, AliExpress, eBay, TradeMe). I looked into it, but the lack of EM shielding is quite difficult to justify, and adding such shielding would make it too big.
We switched from Arduino (which is ARM) to ESP32 and all dependencies compiled and just worked, so I wrongly assumed that it'd be ARM, too. But apparently, their tooling is just really good.
https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-7766-...