CE-Programming
USB Device getting stuck in .waitDma loop after rapid transfers
When sending and receiving a lot of transfers sequentially, usb_HandleEvents can freeze and never return. This can be demonstrated using the attached project, which is a slightly modified version of the link_library example to send a bunch of transfers. To test this program you will need 2 calculators and the appropriate cable. This only ever happens on the "device" calculator, not the host.
I added some debugging logs to usbdrvce and recompiled the toolchain to figure out where it was freezing. It is in the _ExecuteDma function, specifically getting stuck in the .waitDma loop. It does exit with an error if you exit on the host calculator, which is kind of weird to me since the device is the one frozen.
I discovered this bug when adding multiplayer support to my game. Normally, I am not sending nearly this much data. However, after a few minutes have passed (anywhere between 1-20), this happens. I believe it has something to do with the exact timing of send and receive transfers finishing, and it just takes a while to get unlucky. It happens very quickly when I spam transfers like this example, since it's much more likely to hit at the bad time. It also occasionally gives me bad/corrupted data on read instead of freezing, but that is harder to reproduce.
Video of the issue: Note when the device stops blinking. Notably, the host seems to think that the transfer of "H" was complete, and that it was now sending "Q". However, the device has frozen before it even returns from reading "H".
https://github.com/CE-Programming/toolchain/assets/28664080/6c7358cc-f82e-4cdc-8f53-b286e09575fa
Hopefully this is just a coding error on my part, but as of now it seems to be in the library.
