Mode Zero

Any one tried these? Im still looking for documentation... they hid it well.

I got some, probably a couple of years back. Got them flashing some LEDs, and never took it much further than that. Interesting devices, but like most of the 32-bit-and-above microcontrollers, they're a lot more complicated than you'd expect, if you're used to 8-bit or 16-bit devices.

The datasheet is here: https://files.seeedstudio.com/wiki/Seee ... asheet.pdf - all 1,119 pages of it! It does cover several variants though. The one you'll be mostly interested in is the SAMD21G18 variant - the one used on the XIAO.

If you just want to play with one, and are not trying to do anything too demanding, you can use Circuit Python to program it.

Programming one in C or Assembler is more daunting!