USB Host: Dropped/Stuck MIDI Notes

[samblenny]

Currently (10.0.0-beta.2 on Fruit Jam), when reading MIDI messages by USB Host from USB MIDI controllers, note on or note off messages sometimes mysteriously go missing. This also happens for other message types, but note on/off is the most problematic. By "go missing", I mean that the relevant data never shows up as the result of a call to usb.core.Device.read().

I know this is very vague, but I haven't figured out how to reproduce it consistently. My Playground guide at https://adafruit-playground.com/u/SamBlenny/pages/fruit-jam-portable-midi-synth includes synthesizer code where I encountered this problem. The guide also includes a demo video that shows a stuck note (but it took a couple minutes of bashing on keys to trigger it).

I'm posting this issue at tannewt's request to split out one of the points I mentioned in USB Host Improvement Quest Umbrella Issue #10551. The point of this issue is to let people know I'm planning to work on this myself and to ask for comments and feedback.

[tannewt]

I suspect this may be related to us not having buffering. A read() goes out the the device to do the read. If the device doesn't buffer enough, then it likely drops some data because we were too slow to read.

This could maybe be fixed by automatically reading some endpoint types and buffering their responses.