Conflict between Audio Amp Shim and Inky Phat?

Support
1

Hello buccaneers!

I’ve got a bit of an odd one. I’m trying to attach a Button Shim, Audio Amp Shim, and Inky Phat on one poor little Raspberry Pi Zero. The Button Shim I’ve soldered onto the Pi’s underside, and I’ve attached the Audio Amp Shim followed by the Inky Phat on top. My header soldering wasn’t very neat because I had to solder from both directions with the Button Shim in place, but I’ve run a multimeter around the pins and everything seems to be making contact.

With all three components in place, the Inky Phat and Button Shim work great, but no sound comes out of the Audio Amp Shim. If I remove the Inky Phat, the Audio Amp Shim starts sounding immediately.* But also, if I remove the Inky Phat, the Button Shim stops working (returning Errno 121 Remote I/O error)! If I place the Inky Phat ever so gently on the top end of the header (pins 1-6 or so) until it makes contact, the sound cuts out. And the buttons start working. Pull it off, the sound starts again. And no more buttons! While fun, this is not ideal for the feasibility of my project.

Looking at Pimoroni and Pinout.xyz, it doesn’t look like there should be any conflicts between the Button Shim, the Amp and the Inky Phat. Does anyone have any idea what could be causing this, or can anyone replicate?

* I’m testing with speaker-test and mpg123.

Edit: Trusty Mr Piece of Wire and I have discovered that I can mute the Audio Shim if I short pins 12 and 9 or 12 and 14, i.e. GPIO18 to ground. This is expected since I think the Audio Shim uses GPIO18, but could this somehow be connected to the Inky Phat?

2

Hey sorry to necro this thread but I came with the same question and didn’t want to double up.

There doesn’t seem to have been any new information on pinout.xyz since 2021 that would explain the conflict:
https://pinout.xyz/pinout/inky_phat
https://pinout.xyz/pinout/audio_amp_shim

I’m using just those two modules, but the symptoms are the same (with audio stopping when the Inky is plugged in; Inky still works).

What’s interesting is that from a clean startup the DAC still shows up in aplay -l with or without the Inky:

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpihifiberry [snd_rpi_hifiberry_dac], device 0: HifiBerry DAC HiFi pcm5102a-hifi-0 [HifiBerry DAC HiFi pcm5102a-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

and there is no error/difference when running speaker-test with or without the Inky:

$ speaker-test -t w

speaker-test 1.2.8

Playback device is default
Stream parameters are 48000Hz, S16_LE, 1 channels
WAV file(s)
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 128 to 131072
Period size range from 64 to 65536
Using max buffer size 131072
Periods = 4
was set period_size = 32768
was set buffer_size = 131072
 0 - Front Left
Time per period = 0.055585
 0 - Front Left

My only guess at the problem is the hifiberry-dac overlay causing a conflict, but I have no idea where I’d start to verify if that’s the case.

I don’t think it’s a power supply issue, I’ve been using a 5.1V 2.5A micro-USB plug pack.

FWIW I’m on a Pi Zero W running Bookworm.

3

I can’t say what was happening with your button shim, but I’ve found my problem.

It turns out that plugging in the Inky squishes the header pins in just enough that the shim isn’t making proper contact. If I apply a bit of torque to twist the shim against the pins it works now!