Datasheets
- ATSAMD21 Datasheet (the main chip on the Feather M0)
- Fritzing object in the Adafruit Fritzing Library
- EagleCAD PCB files in GitHub
Note AREF in the diagram should be marked PA03 not PA02
Firmware
Feather M0 Bootloader - You'll need to program it in using an ST-Link, JLink or other SWD-capable programmer. HEX available in the github repo