Implement DAC-based audio (audioio) on Espressif

[dhalbert]

The DAC(s) support DMA, but it's not in the ESP-IDF API yet: espressif/esp-idf#6333. So we would wait for that.

[275RR]

any update on this? I have a a MagTag

[ladyada]

i think we were seeing weird results, when @jepler is back we can follow up with espressif on whether they fixed DMA DAC support on the S2

[gpeyton]

@jepler @ladyada any update on this?

[ladyada]

@gpeyton since you are bumping - please check with espressif if they have DMA support for the ESP32-S2 DAC, that was our hold up as you can read above

[tmkasun]

@ladyada and team, it looks like DAC DMA is now supported in Espressif: https://github.com/espressif/esp-idf/blob/master/components/esp_driver_dac/esp32s2/dac_dma.c.

If you could provide some guidance, I’d be happy to work on adding this support to CircuitPython.

[tannewt]

@jepler Do you have a WIP branch somewhere that @tmkasun could start with?

Otherwise @tmkasun I'd suggest looking at how I2SOut is implemented and convert it into audioio.

[jepler]

@tannewt no I don't think I have any WIP branch related to this

[jepler]

The esp-idf docs make it sound like we would want to use continuous dma mode with asynchronous writing: https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/api-reference/peripherals/dac.html#continuous-wave-output-continuous-dma-mode

the on_convert_done callback would be comparable to the function i2s_event_interrupt providing the next buffer to be filled in a background callback.

Thanks for looking at adding this to CircuitPython @tmkasun !