Feature request: CircuitPython support

[pdp7]

I asked CircuitPython core developers @tannewt and @dhalbert and they indicate that it should be possible to add support in CircuitPython for the Doppler even though it does not have external SPI flash. The SAMD51 in the Doppler has 512KB internal flash which should be sufficient to create an internal file system for CircuitPython.

Dan wrote in Discord:

We had internal flash only for the SAMD51 before we got SPI and QSPI flash implemented. A good guide would be to look at the atmel-samd/boards/trinket_m0/mpconfigboard.* or other non-Express boards. You'd need to set LD_FILE = samd51x19-bootloader.ld (and double-check that file, which hasn't been used for a while and might need updating) and also set INTERNAL_FLASH_FILESYSTEM = 1.

This is the config for the Trinket M0 that Dan referenced which only has internal SAMD21 flash:
https://github.com/urish/circuitpython/blob/master/ports/atmel-samd/boards/trinket_m0/mpconfigboard.mk

Here is a SAMD51 board but it does have external SPI flash:
https://github.com/urish/circuitpython/blob/master/ports/atmel-samd/boards/itsybitsy_m4_express/mpconfigboard.h

Dan and Scott both suggested jumping on the Discord channel for future questions:
Adafruit CircuitPython Discord channel #CircuitPython

24/7 chat and support on CircuitPython including a weekly podcast.

[tannewt]

Thanks @pdp7 ! We're here to help! Just let us know what questions come up. Looks like the Doppler already uses the UF2 bootloader which is exciting!