Adafruit Feather M0 Basic Proto - ATSAMD21 Cortex M0 has a free prototyping space on the board. Feather is a new development board series from Adafruit. As the name suggests, Feather boards are thin and light. Feather is designed to be a new standard for open source development platforms.
Feather is the new development board from Adafruit, and like its namesake it is thin, light, and lets you fly! We designed Feather to be a new standard for portable microcontroller cores.