AI Thinker support

[unknown0816]

• Added AI Thinker ES8388 Board support
• Fixed volume setting of ES8388

[alexyao2015]

What great timing! I was looking into adding this today too. I gave your branch a try and it works well with the exception of the psram being turned off. Suggest you set CONFIG_ESP32_SPIRAM_SUPPORT to y so there aren't out of memory issues.

[unknown0816]

I'm happy to hear, that it works well.

Regarding you suggestion: As far as I understand is this a sdkconfig setting. So everybody can just set or unset this. I guess I could add ai_thinker example sdkconfigs (with and without this setting). Is this what you would like to have?

[alexyao2015]

Something with the scaling factor of the volume isn't right. It seems like anything below 80 is inaudible.

[CarlosDerSeher]

Ok I double checked the code and it seems @unknown0816 volume is controlled both digitally AND analog? Maybe this is the problem? So try setting analog gain to it's max value for this board and control volume digital only?

[alexyao2015]

The datasheet is not well written but I see here that the left right is set to 0 gain and the volume only adjusts the main 4+5 gain. https://github.com/espressif/esp-adf/blob/33ba0c5c698b6719e0cd8e2bd97d8e4c5a13d9d2/components/audio_hal/driver/es8388/es8388.c

[unknown0816]

I know that the scaling is not perfect. For me anything below 50 is mute and anything above 70 is not bearable. I guess it would be possible to modify the lower and upper case to have a more usable scaling, but that would not be datasheet conform.

I tried, to only set 4+5 respectivily 24-27, but here I always had no good scaling, too.

[unknown0816]

I did an experiment, which worked kind of well:

  int inv_volume = (100 - volume)*0.5;
  res = es_write_reg (ES8388_ADDR, ES8388_DACCONTROL5, inv_volume);
  res |= es_write_reg (ES8388_ADDR, ES8388_DACCONTROL4, inv_volume);

  volume /= 8;
  res |= es_write_reg (ES8388_ADDR, ES8388_DACCONTROL24, volume);
  res |= es_write_reg (ES8388_ADDR, ES8388_DACCONTROL25, volume);
  res |= es_write_reg (ES8388_ADDR, ES8388_DACCONTROL26, volume);
  res |= es_write_reg (ES8388_ADDR, ES8388_DACCONTROL27, volume);

Playing around with the 0.5 and the 8 will influence the scaling of the volume. For me this works quite well, but this could be different from board to board, I guess.

Edit: 0.33 and 6 works good, too.