October 10, 2023
The RP2040 has a well documented USB subsystem, and there is plenty of source code that does not look like a huge mess.
There is also "TinyUSB" which supports not just the RP2040, but also the STM32F103 chips (i.e. the "blue pill"). There is source code (from ST?) for the STM32, but I have spent some time looking at it, and it seems to have been written under contract by men from Mars. TinyUSB looks more civilized by a long shot.
The RP2040 documentation recommends looking at the "low level" example provided alongside of their SDK, namely:
pico-examples/usb/device/dev_lowlevelSo, I could look at the RP2040 first, then perhaps take another look at the STM32F103 and perhaps also other big brothers in the STM32 family.
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