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Thread: Teensy 3.2 SPDIF and I2S

  1. #1
    Senior Member
    Join Date
    Dec 2015
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    125

    Teensy 3.2 SPDIF and I2S

    Hi all,

    For one of the projects I am working on I need to connect to two computers via USB, one for input, one for output. I'd like to transfer the signal between the two Teensys digitally to avoid noise. Currently I have a Teensy 3.2 as the input, and a Teensy 4.0 as the output. I'd like to stick with the 3.2 on the input for now, though I should probably do some experimentation to see if changing makes more sense.

    SPDIF seems like a good choice, since in theory I can transfer the required two channels of audio rather easily. However, I'm also using the audio board on the input Teensy, which means I need SPDIF and I2S at the same time. I know that normally this isn't possible. On another thread long ago (I can't seem to find it again, my search skills are failing me) someone (Paul I vaguely recall) mentioned that it would be possible to modify the audio library such that it would allow both SPDIF and I2S on the 3.2.

    So...am I remembering this correctly? And if I am, has anyone attempted this, or has any pointers on how to accomplish this?

    Thank you!

  2. #2
    Senior Member
    Join Date
    Feb 2017
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    413
    I used SPDIF I/O and Audio Board I2S I/O in this project: https://forum.pjrc.com/threads/45394...hlight=toslink

  3. #3
    Senior Member
    Join Date
    Dec 2015
    Posts
    125
    Thanks for the reply! I did look at your thread earlier, but thank you for the reminder. Unfortunately I'm trying to do something a bit different in that I'm trying to use the on chip I2S interface to generate the SPDIF signal without going over a proper I2S connection. If that makes any sense. From my recollection someone once mentioned that it might be possible, using I'd guess pin 15 as the SPDIF out.

    This has got me thinking though. In the event I can't get this to work, perhaps I could use an i2s_quad on the output of the main Teensy, with one data pin going to the audio board, and the second (along with the clocks) going to the other Teensy that's running an i2sslave object.

    I know that running the Teensy with something else as the master clock can cause some issues with some modules, would USB I/O be safe though? My gut says yes but I'd love to know for sure.

    Thank you!

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