dac cosine and dma write, PR?

[NicasioSirvent]

Hi, first time contributor, so best i ask here first...
I needed this functionality, so i have extended machine_dac to include cosine and dma write, following ESP-IDF new sdks.
Testing w oscillocope and esp32s2, cosine can go to 300Khz full amplitude and to 1Mhz or more with 16db att.
And write_continuous can be used to write from dma custom waveforms from lists...etc, at similar speeds.
So, IMHO, heavy improvement versus the time-interrumpt based code in the models with dac support (esp32 and esp32s2)
But... before open a PR, best to ask here: is this PR ready?

https://github.com/NicasioSirvent/micropython/tree/esp32-dac

Thanks.

[Josverl]

Interesting that you bring this up
I have not looked at your implementation in detail, but I recently created a module to access the cosine generator in just MicroPython with feature parity (I think)
I have not added DMA, so that should be considered separately

My rationales for the cosine generator:

• a python version can be either frozen or MIP installed, a C version needs to be conditionally compiled, or grows the firmware.
• the hardware cosine generator is only available on a few older MCUs of the ESP32 family (AFAIK, only the ESP32 and the ESP32-S2 , but I've not checked all the spec sheets manually)
• I am not aware of requests for this feature before (though clearly I had a few weeks ago)
• if prefer a Python based implementation over C implementation unless there is a very clear advantage for one (simplicity, maintainability, composabilty)

so I'm not sure if it's worth it to weigh down the firmware and C code based on the above rationale.

[NicasioSirvent]

Hi Jos.
My rationale was that i am using the code for weeks, and it is a pity that micropython doesnt include a real dac cosine and dma function and only a dac.write() from 2017 that can go up to a few khz.
It compiles only if the mcu is esp32 or esp32s2, but im not aware of size constraints or requests for this feature.

But.., if a better solution is on the way, perfect.
I will keep using my code until a better solution is ready, and later, maybe, transform in a module.
Thanks.

[Josverl]

No problem,
It's the same solution, written in a different language.