This project is a small dongle carrying a SAMD21 from Atmel along with a CR2032 battery holder and USB b port for use as a portable fusee launcher.
I built it to get a little more familiar with the Cortex M0 offerings from Atmel, as well as to make myself a nice, compact device that I could use for Switch experimentation as well as other projects.
This project is using the UF2 bootloader, which is the most amazing idea that anyone has ever come up with - thanks, Microsoft! The UF2 bootloader impersonates a virtual flash drive when plugged into USB and reset is double clicked, allowing reading and writing firmware with a simple drag/drop operation. Very slick!
The project is also compatible with the Arduino platform using the bossac loader. Personally, I use an STM32 blue pill flashed to CMSIS-DAP to do my low-level programming, but for a simple setup Arduino can't be beat!
The discussion thread of me chatting during the build is on gbatemp
And if you would like to purchase a completed board, the Paypal Buy now button over here is best for me (lowest fees)
And the board is certainly available on Tindie
Firmware files for the three most popular loaders (hekate, ReiNX, and SXOS) are found below in the files section. To switch, plug the board into USB, double click reset, and drag the 3 files from inside the zip onto the flash drive that pops up (Drive name is FIRMWARE)