Replicating the Trinket M0 Express Hack

Published on 2017-10-02 in PewPew FeatherWing.

It would be great to have more memory on PewPew, so I decided to try and replicate the  Trinket M0 Express hack, only with my bare chip. To do that, I need a flash chip. The original hack used a S25FL116K0XMFI043 chip, but of course I don’t have that. But they should all be pretty much the same, no? So I tried with a W25Q32FVSSIG instead:

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The connections are pretty much what you would expect:

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And the board definition is in this branch:  https://github.com/pewpew-game/circuitpython/tree/trinket-m0-express

After compiling and flashing the firmware, it… doesn’t work. I mean, the CircuitPython itself works and shows me the REPL console, but there is no USB disk. And it’s easy to see why — there is a number of files in the_boards _directory that contain flash chip definitions, and that you include in your board definition files. And guess what, the chip I’m using is not there. So I have two options now: dive into the datasheets and prepare my own flash definition file, which would be the “correct” choice, or order a flash chip that is compatible with what is there already, then wait a few weeks for it to arrive and try again, which is the “lazy” choice. Guess which one I’ve chosen.

Since I’m waiting for the PCBs and parts for the next version of PewPew anyways…

Update: So I overcame by inherent laziness and created a flash file for the W25Q32BV family. And what do you know, it works!