Hello,
On 08-12-2020 16:44, Bill Purvis wrote:
  On 08/12/2020 15:30, Florian Paul Schmidt wrote:
  Hi,
 if the USB device id is different for the two usb devices then you might
 just write a custum udev-rule that loads the snd-usb-audio module with
 different card index parameters..
 Regards,
 FPS 
 That's my problem, the keyboards are identical models and the only thing
 that
 will distinguish them is the slot they are plugged into. I haven't got
 as far
 as plugging both in and looking if there is a correlation between the
 information
 provided by lsusb and the Alsa slot id. I think I can get them on
 separate hubs
 which might be useful. I know very little about what goes on when
 devices are
 initialised. If all else fails, I'll have to plug one into an Arduino
 and use
 that to shift the channel number, but I had hoped to avoid going that far!
 Bill
  
If the keyboards are on different USB buses you can use that difference
to distinguish between them. Like Florian said you can use Udev for
this. Did a quick search and this might be useful:
https://github.com/dh1tw/remoteAudio/wiki/Persistent-USB-Mapping-of-Audio-d…
lsusb can tell you which keyboard lives on which USB bus, bear in mind
that different USB ports can live on the same bus. So the trick is to
find out if there are USB ports living on different buses and connecting
the keyboards to those specific ports.
Best,
Jeremy