PINE64 A64-LTS (pine64-a64lts)
The Pine board has a 3.3v UART on the EXP 10-pin header.
- Pin 6 is GND
- Pin 7 is TX
- Pin 8 is RX
Install alsa-utils with apk, launch alsamixer, unmute (press M) "Headphone", "AIF1 Slot 0 Digi" and "DAC" (or "DAC Reversed"), increase the volume of "Headphone" to something over zero.
Then you can play some music (e.g. a .wav file) with aplay.