Pico Audio - which pins are used?

I’m working on a project to mount a Raspberry Pi Pico and a Pico Audio to a ISA card to be used inside a PC. This requires me to connect these two devices on the ISA card, which is shown in the following photo.

From looking at the schematics for the Pico Audio I’ve joined the I2S pins (12, 14, & 15) along with VSYS (39) and GND.

My understanding was that this would be enough to allow the two boards to communicate and work together. However this does not appear to be the case.

When I connect the two boards directly together (not on the ISA card) they work as expected. However if I just try and directly connect the pins I’ve listed above, I get no audio output.

This suggests to me that some additional pins also need to be connected?

Any help would be extremely useful


This is the opposite side of the ISA card, with both boards mounted

There is a pinout at the bottom of the product page. You may need to wire up the Mute pin.

Thanks for the suggestion @alphanumeric

I’ve also connected this pin, sadly I’m still not hearing any audio output.

I’ll go and double check my connections are correct and connected later, as I can’t imagine there are anymore possible connections missing if they’re not listed on the schematic!

One thing that has caught me out with Pi Hats wired up like that, is a missing ground connection. On the Pi and Pico all the grounds are linked together, it doesn’t matter what one you use. On that Hat or Pack, that’s not always the case. It’s assumed they will all get linked (connected to ground) when its plugged into the Pi or Pico.
You may have to wire all the grounds together on the Pico Audio. Or figure out which ones are used?

Success - it appears that the mute pin needed to be connected up.

For reference - I’ve found that all of the ground pins on the Pi and the hat are connected, which is good

Thanks for your suggestions and help with this all

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