It is an interesting question.

We know that you can get a GPIO card + HDMI I2S output working at the same time : https://lists.audioinjector.net/pipermail/people/2020-March/000021.html

The default answer is always no. However it may have work arounds ... but I am not 100% sure it can be done.

The first problem would be in probing the sound card, see the ISOLATED sound card probe for example :

https://github.com/raspberrypi/linux/blob/rpi-4.19.y/sound/soc/bcm/audioinjector-isolated-soundcard.c#L123

There the CPU/platform and codec data is populated. Will ALSA SoC spit the dummy if two cards are registered for the same I2S bus ? Most likely. If not, then it may overwrite the SoC core with the most recent one added. In which case, both would be plugged in but only one would be active.

Imagine however this worked. For example, imagine you worked out how to register one for playback and one for capture.

The next problem is who will control the clock ?

I suspect with a lot of hacking you could find limited functionality. However my experience is that Linux frowns upon upstreaming hacking ... which means you could get something to work on your desk, but it wouldn't become mainstream :)

However I can see lots of ways to try work arounds. For example, imagine you had many of the same sound card hooked up. Say you wanted to do DAC only. You could find a way to output with one card as master and the others as slave ... however in this case all output cards would play back exactly the same saples - but their mixers should be independently controllable :)

Matt

Hi,

 

I’d like to ask if it is possible to have a dual configuration, i.e. enabling both the stereo and the octocard (in config.txt) ? My guess is that the kernel will try to initialize the chipsets and fail on the one not connected.  Has anyone tried this ?

 

Regards

/Rob

 

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