Multichannel USB audio play and record

[ccrome]

Update USB descriptors to have variable number of channels on TX and RX

Added support for defining multiple data pins. This allows use of more than one TX and/or RX pin.

Allow for choosing different USB sample rates.

this commit goes hand-in hand with https://github.com/PaulStoffregen/Audio/pull/470

I have also created a patch that applies to the 1.58 release as opposed to the master. It's available here https://github.com/ccrome/cores/tree/ccrome/add-multi-channel-usb-1.58

The point of that one is because I don't know how to compile the current cores/master because of the c++17 updates.

[h4yn0nnym0u5e]

As noted in this forum post , this multi-channel USB PR does not appear to work. The OP seems uninterested in fixing the issue.

The updates discussed on this thread do seem to be satisfactory. If Paul gives us a word of encouragement on that thread, and maybe a hint of how to package up a slightly complex set of changes, we can definitely rustle up a set of PRs pretty fast, I'd think :)

[PaulStoffregen]

@h4yn0nnym0u5e - Right now I'm merging only bug fixes in prep for 1.60-beta1. Will merge new features for 1.60-beta2, but to start the path to 1.60, I want the first beta to focus on fixes without adding stuff.

[h4yn0nnym0u5e]

Completely understand.

Just wanted to flag that this PR is not (AFAIK) worth spending time on, and that IF you wanted to include the alternate one at some stage in the 1.60 beta program, some discussion and preparation would probably make your job easier - I'm sure alex6679 and I are willing to put some time in to get it to an acceptable state!