Add support for PT8211 DAC

[whc2001]

UNTESTED!!! It compiles, but it's not tested with real hardware yet as I'm physically away from my home. There is a small possibility that it just does not work at all.

• Added a flag (CONFIG_I2S_USE_MSB_FORMAT) for using MSB format instead of standard Phillips format for I2S. This flag will be triggered by the selection of the PT8211 audio board.
  • Note that this is not exactly the same as the LSBJ format PT8211 demanded. It's only that their timing is equivalent under the native bit-depth (PT8211 is 16 bit, and this project also uses 16 bit). The Arduino I2S library is doing this so I assume it's acceptable.
• Added PT8211 audio board definition. I have included a mute output pin with configurable GPIO number and enable level, despite PT8211 don't even have any kind of control input. It's intended for something like an external amplifier.

[CarlosDerSeher]

Looks good but I'd prefer to try with real hardware before we merge

[whc2001]

Looks good but I'd prefer to try with real hardware before we merge

Great, thanks! I'm gonna do that ASAP after back home.

[whc2001]

Tested. There is a slight hiss but it goes away while RESET is pressed, maybe it's WiFi interference.

https://github.com/CarlosDerSeher/snapclient/assets/16266909/760005c6-78a7-4f50-8082-76eb1f8dae64

[CarlosDerSeher]

@whc2001 Could be interference as your setup isn't perfect with the antenna that close to the analog part. What you could try is lowering wifi output power from menuconfig and see if that improves quality.

[whc2001]

@whc2001 Could be interference as your setup isn't perfect with the antenna that close to the analog part. What you could try is lowering wifi output power from menuconfig and see if that improves quality.

Yes. I have tried to lower the TX power from 20dBm to 10dBm and the noise mostly went away.

[CarlosDerSeher]

I guess we are done here then. Thanks for your contribution!