[matthewvia]

Thanks for your interest! I didn't want to be dependent on the number of hardware timer captures, so I did actually start with a system like you describe, with a single timer/compare and managing a linked list of upcoming events. On compare interrupt, it would iterate through any events that had passed in time, carefully setting the compare register each time to avoid potentially missing any changes. I actually thought it was pretty straightforward, but it had the effect of skewing similtaneous outputs: Each iteration cost almost a microsecond, so having 4 similtaneous changes would actually be splayed over 3.5ish uS.

Instead I am now effectively bitbanging the outputs with the dma controller. I manage a circular buffer of gpio pin changes (16 bits for "turn on", 16 bits for "turn of") for about a 128 uS window, and the DMA reads on a .25 uS interval from that buffer. There is a lot of complexity in ensuring the buffer's contents is accurate with event changes in a race-free manner, and testing that sufficiently has been where I've had to put most of my effort.