The plan for this week had been for me to finish up the APU and then work on the sprite engine. Unfortunately, I hit a hard wall with communication between the APU and the CPU. Some progress has been made on that front, and I’m now able to send a 1KHz sine wave from a C program through the APU driver to the APU. Unfortunately, some corruption issues are preventing non-static data from being sent through.
Still, this does mean that the APU is fully written, just not fully debugged. The user space library for the APU is complete and tested, sending signals to a user process as a kind of user-mode interrupt works great. The kernel module is mostly written with the aforementioned corruption issues. The hardware, after some intense debugging and scrutiny from both Joseph and myself, seems to be fully operational.
I suspect that the issue is with the kernel module, and not the user space library or test program. It seems likely that I haven’t set up the APU kernel buffer for DMA correctly, and so that will be where I investigate next. The running theory is that our level 1 cache isn’t being flushed, and so we’re only getting some of the samples out of the kernel buffer into the APU, and are thus seeing corruption.
Thanks to the slack time we allocated for the end of this semester, there’s still a good chance that we’ll be able to get everything done on time. The plan for this coming week is for me to fix the APU and then deal with the sprite engine in any remaining time I have. After that, I’ll have a week to finish the sprite engine and two to work on the test game.