ATSAMD21E18A Dev Board Pins and Bootloader


I'm having a little trouble sifting through the github and finding what I need.

I want to make a board using the ATSAMD21E18A but I can't figure out which bootloader to use or where the list of pins would be for that micro, i.e. A4 = Pin 19, or something like that. Could someone point me in the right direction?

Thanks :slight_smile:

Hi breadborder,

If this is your first Arduino compatible board then to begin with it's easier to use the bootloader from an existing SAMD21E18A board, such as the Adafruit Trinket M0: Adafruit Trinket M0 - for use with CircuitPython & Arduino IDE : ID 3500 : $8.95 : Adafruit Industries, Unique & fun DIY electronics and kits and use the board's schematic as a guide.

Note that the Trinket's bootloader will pulse it's status LEDs during an upload, it's therefore necessary to either match your hardware design to these LED outputs, or alternatively recompile and flash the bootloader with reconfigured pins. Your board should also provide access to the SWD port to upload the bootloader and a reset button to put it into bootloader mode.

The bootloader and sketch code are separate. The Arduino pin definitions while running a sketch can be found in the "variant.h" and "variant.cpp" files in the Arduino core code for each board.