I assume there is probably some way to hook up the dma hardware and gpio state machine to get perfect timing of delta sigma modulated audio with no involvement of the CPU.
Hrm there probably is, but the pio commands don't have addition so the integration part of the delta sigma modulator could be trouble. You could preprocess but it would create enormous files.
I did do a delta sigma using the pios but fed via cpu, essentially used just a look up table of amplitudes that fed a bitstream into the pios to get a psuedo 133 MSPs dac.
I think it's possible to get a bit-perfect output sequence by having a bunch of lookup tables for waveforms, and then another table allowing you to chain together a sequence of waveforms (and phase, via offsets into waveforms). That should let you generate any sequence that a perfect delta sigma modulator would have output, with far lower ram requirements than the whole bitstream.
