AIY Hat Alsa Mixer Blank

[paulw25]

I am using the Voice Hat with my own software. The problem I have is that the alsa 'amixer' command returns nothing. No error. Just blank. Following this my python script errors as it is unable to find the Master mixer. The fix for this is to run a speaker-test, and then miraculously the mixer appears and all is well. I have studied the speaker-test source code but can't see anything obvious that is initialising the master mixer.

Has anyone come across this problem before?

Paul W

[paulw25]

As usual the answer to this is in the documentation!

https://alsa.opensrc.org/Softvol

Note:The new volume control won't appear immediately! Only after the first usage of the newly defined device (e.g. with speaker-test), should amixer sget Softmaster display the new control. Mixers that were already started before the first usage (like KMix) have to be restarted to adopt the changes. If the new control is still not there, try restarting ALSA or your PC.

I built the speaker test into my code, but it felt like a bit of a hack, so I was pleased to find this explanation.