Hi,

Thank you very much for your report; the information is very useful to
improve the driver.

> First I tried with the internal speaker playing WAV file with
> audioplay. But there was no sound at all.
> Then I set the volume with mixerctl up to 250,250 (default is 80,80).
> I could listen to the sound putting my ear on the speaker.
> I think it is no good because 250,250 is the maximum level.

I think I know what's the problem with the built-in speaker, it needs
special configuration due to it being a mono device connected to
stereo outputs.

> Next plugging stereo headphones, it worked with no problems.

:-)

> Setting the volume to 80,80 again, it was enough to use with my
> headphones, and 250,250 was to much.

Yes, 250 is expected to be a high volume. It corresponds to +18 dB.
The 0 dB point corresponds to value 176, so this should be the highest
possible value that can be used without distortion. The value of 80
corresponds to -36 dB.

Thinking about this, it would be nice if mixerctl(1) could use dB
values instead of the 0-255 scale; this would be good for consistency
between different audio devices.

> I could see the message on the shell.
> " i2s0: powering down
>   dac3550a0: entering low power mode"

Nice!

Thanks,
Marco