MIDI and multiple stereo output

M

mark63

Active member
I am totally new to usb audio. i have read a lot of threads. i also found the design tool.
it seems what i want is not possible with teensy 4.1. I want to make 2 usb midi I/O . that is no problem since i already tested more of them.
But i also want 2 or 4 stereo audio outputs. And all need to work at the same time.
i do not need inputs nor fancy things. just an usb audio device with 2 or 4 stereo outputs.
The channel concept is not clear to me either. so either in would need 4 audio objects with stereo output. or 1 audio device with 4 independent stereo outputs.
I get that i need multiple i2s.
would this be possible? or is that using too much processor power and memory?
i would imagine that standard chips would exist that offer this.
the audio i need is 16 bit 44khz.
I hope some expert can tell me. the fact that it does not exist yet probably means it is not possible but since in am new i want to be sure before i give up this route.
 
Multiple I2S is well supported (in master mode, where Teensy creates the I2S clocks). There are 2 separate I2S ports. The first port can do up to 4 stereo (8 channels) in 1 direction. The second port is limited to only 1 stereo (2 channels).

So far, USB audio is limited to only stereo. Several people have done some initial work towards 8 channels, but so far only limited results. The official code which ships with the Teensy core library supports only stereo audio over USB.
 
thanks for your reply. So the first I2C port would be sufficient for me since it can do 4 stereo. But what you say is that it requires a modification of the usb code that handles the additional channels right? So that is what the users tried in the thread i found. But nobody solved it. That is a pity since i really like the Teensy.
 
Would that be this thread? or maybe this one? mcginty and I were getting quite close towards the end of 2022, but he dropped off the radar this year for reasons unclear, and the job is only about 90% (?) done.

If you fancy posting on one or other of the above threads, even just to ask "any progress?", I'll try to guide you through where we've got to and what I think is left to do. You may want to try the stuff we did achieve, because it might work for you as-is, though you will have to get your hands a bit dirty making a Frankenstein's monster of a Teensyduino.

Long story short, I think we only need someone with (a) a bit of time, and (b) a good understanding of USB descriptors and USB audio sync, and we could be good to submit a pull request to get multi-channel USB audio into Teensy. Unfortunately, I'm not person (b)...
 
thank you for your reply. yes those are the threads i found. i do not have deep knowledge of B but i did other usb device devices before. i also have some books about it. what i will do is this : i check out usb audio , then go through the threads again to see what was changed and why. i see there is no easy route so i need to do it the hard way. but before i invest a lot of time i will check some other routes like psoc and others. a simple AVR can do 1 audio, so maybe i settle for that. Since commercial devices exist it should be doable. i will reply in the other threads if i have questions or solutions.
 
You must log in or register to reply here.
Back
Top