Monday, May 28, 2018

U2F One Key

MX U2F authenticator

My attempt to build a U2F key based on the design and firmware of the U2F Zero.

It mostly works, but I did not add a debug header so can only program it via the factory USB bootloader, which limits the size of the firmware. I can only load a stripped down version of the firmware.

The basic circuit is the same as the U2F. The microcontroller needs very few external parts to work.

I used 3 separate LEDs instead of the single RGB LED on the U2F Zero. The MX switch footpad allows the board to be flipped and the switch mounted on either side. I can have the ICs exposed on top or hidden under the board.

These PCB's were produced at This was during their $5 promotion. The promotion has since ended, but for small orders they have the cheapest DHL shipping.