(deleted)
what you smoke today must stay illegal
Found a picture of the underside.
The site where I found this pic offers a schematic and data sheet, but they are the Sparkfun samd21 breakout. Perhaps the board above is a clone of that, but clearly not identical.
I finally got an answer from the eBay vendor:
Hi, does this board have Arduino Zero bootloader or other Arduino bootloader installed?
Hello many sorry for the late reply.
Yes,it has installed.
And here are document:
SparkFun SAMD21 Mini Breakout - DEV-13664 - SparkFun Electronics
GitHub - sparkfun/SAMD21_Mini_Breakout: A miniature SAM21G Breakout, in the form factor/pin-out of a Pro Mini.Hope it will help you.
Regards,
Cindy

