Turning rpi with octo into a windows audio interface

[thewizard240]

Raspberry pi and octosound card , works great, all the ins and outs are fully functional. I'm trying to use config_fs and the otg usb gadgets to configure 8 UAC2 audio devices with the raspberrypi zero to make an audio interface. Windows doesn't recognize it, and I'm wondering how to configure the pi so that windows recognizes it as a composite USB device with 8 generic UAC2 devices?

My plan was to have alsa route the 8 outs and the 6 ins to 8 UAC USB OTG gadget devices (which ALSA recognizes on the pi's side) and be able to use the pi as a programmable audio interface, but it hardly works on windows, does anyone know how I'd set it up to work properly?

[flatmax]

Hi there,

I think you can do this with a Pi Zero. It has an OTG USB connection. This will allow you to put the Pi into device mode. At that point you should be able to configure the UAC2 audio device.

I am not aware of how to put the Pi2 or Pi3 into device mode over USB ... is it possible ?

Once you have successfully setup your UAC2 device, perhaps you should test first with another Pi and then test a Microsoft box ?

From my experience, once setup, it runs straight away ... my Linux Desktop connects nicely with it.
Don't forget that once you have the UAC2 device setup, you need to arecord from the UAC2 device to the octo device and play ... it would be best if you can do this synchronously :
UAC2 in -> Audio Injector Octo output
Audio Injector Octo input -> UAC2 out

thanks
Matt

[thewizard240]

I'm sticking with a pi zero since it doesn't have a USB hub chip, thus allowing OTG, and I appreciate the pointers with arecord , I was wondering how to route the audio between octo and UAC2.

The pi does show up as a uac2 device on all of my linux boxes (various debians), and even macOSX, but not windows (windows can't enumerate it and get drivers for it, giving a code 10)

I've read in other articles where people are trying to configure the pi as a composite USB device, being a network device AND serial, where they had to set flags and IDs to tell windows that it was A) a composite device and B) a kind of network interface that windows had drivers for already

So I'm wondering how I can configure the filetree in /sys/kernel/config/usb_gadgets to reflect values that windows can read and recognize the device as a UAC2 device, as far as I know windows does have support for it, and seeing that it works on non-windows machines I'm sure all the code is in place and would work if windows would make an attempt to try to connect to it?

[flatmax]

hmmm ... I would like to set up a UAC2 device on a zero myself and be able to write in exactly how to do that ... it is a little involved - right.

I couldn't understand whether you could use arecord with your linux boxes to record inputs on either the desktop or embedded system ?

Matt

[thewizard240]

I did get arecord to work on linux and OSX machines

linux UAC2 soundout > arecord > alsa UAC2 input

and vice versa with

raspberry pi uac2 out > arecord > linux uac2 input

I've only tested with 2 ins, and 2 outs though

arecord routing being configured on the pi

[flatmax]

Nice work - do you have a script you would share with us for setting up your UAC2 devices ?

thanks
Matt

[widdly]

Another option would be to use the ethernet port and netjack instead of the USB otg. Linux, windows and OSX all have jackd netjack clients