No audio through jack despite config audio=on, raspi-config also fails

Question

I am trying to get sound out from a Raspberry Pi zero with RaspiOS bullseye. I have enabled the alternate functions and use a RC filter to get an audio signal to some earbuds. However when I try to play anything using aplay it doesn't work.

I have the following clues:

I made sure that dtparam=audio=on is present on config.txt.

When I try to force 3.5mm from raspi-config menu it seems that there is some problem. When I click "S2 Audio" the screen flashes for a few seconds and it goes back to the main raspi-config page.

When I try alsamixer I only get HDMI as an option. The same happens when I run aplay -l

Any idea on what can be wrong? I tried reinstalling the OS several times and it didn't help.

Answer 1

You need to add the following to config.txt (assuming you are using PWM 12 and 13):

dtoverlay=audremap,pins_12_13

Test using:

speaker-test -c2

Info:

pi@raspberrypi:~ $ dtoverlay -h audremap
Name:   audremap

Info:   Switches PWM sound output to GPIOs on the 40-pin header

Usage:  dtoverlay=audremap,<param>=<val>

Params: swap_lr                 Reverse the channel allocation, which will also
                                swap the audio jack outputs (default off)
        enable_jack             Don't switch off the audio jack output
                                (default off)
        pins_12_13              Select GPIOs 12 & 13 (default)
        pins_18_19              Select GPIOs 18 & 19