Fix CDC FIFO used getting out of sync #711
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... by deleting it. I found a .blit that would reliably fail to flash (99% bug). Adding any extra logging to the USB code caused it to work, as did writing extra data at the end. Then I noticed that the read index was sometimes behind the write index by several entries, but "used" was 0. I think this is what was happening: - FIFO write is called from the USB interupt - write increments "used", read decrements it - those inc/decs are actually "load, add, store" - interrupt can happen in the middle of that - write increments from interrupt in the middle of the decrement in read - "used" is now too low So, I deleted the used variable and checked the read/write index instead ... and that .blit now works reliably.
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I think it might work!
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Thank you. RIP 99% hangs, nobody will miss you 😆 |
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... by deleting it.
I found a .blit that would reliably fail to flash (99% bug). Adding any
extra logging to the USB code caused it to work, as did writing extra
data at the end. Then I noticed that the read index was sometimes behind
the write index by several entries, but "used" was 0.
I think this is what was happening:
So, I deleted the used variable and checked the read/write index instead
... and that .blit now works reliably.
This hopefully fixes the "99% bug"... I've tested this with my usual "flash everything" script (86 .blits this time).