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Thread: Audio over Serial

  1. #1
    Junior Member
    Join Date
    Sep 2019

    Audio over Serial

    Hi all - this is more of a would this be possible/what are my first steps question;

    I want to send audio between A and B digitally using two Teensy (bidirectional).

    Is there a serial node available that I could use to send the bit stream over one wire from one teensy to the other, and another wire in the opposing direction. I understand that Teensy has the capability to send and receive data serially at these rates, Just need a pointer as to how I can go about implementing this. The follow on question would be could I then have multiple (6) teensy's sending and receiving data from a central teensy that hosts a matrix internally.

  2. #2
    The Teensy 4.0 chip supports SPDIF which is exactly what you want for point to point as that is what it was designed for. But I believe you'd have to write your own drivers for now for the Teensy.

    The second question is a bit more complicated as SPDIF isn't multidrop so you'd probably need to add one of these, or something similar

  3. #3
    Senior Member
    Join Date
    May 2016
    The Teensy Audio Board/Audio Library supports SPDIF IO, and multi-channel TDM (time-division-multiplex) through the CS42448 chip...

  4. #4
    Quote Originally Posted by DerekR View Post
    The Teensy Audio Board/Audio Library supports SPDIF IO, and multi-channel TDM (time-division-multiplex) through the CS42448 chip...
    From Paul himself last month :

    There is the small matter of (so far) no software support for Teensy 4.0's S/PDIF peripheral in the audio library.

    Given the power of the Teensy4.0 for audio, I wouldn't think it a good idea to start from the lower power modules for anything serious, which the OP's description sounds like.

  5. #5
    Join Date
    Aug 2016
    bi-directional causes problems if you need synchronised audio. even though the two clocks are crystal locked, they will drift over time. the usual solution is to use a master clock, usually generated by one of the sources, or as a studio standard signal.

    unfortunately, synchronised external audio isn't in the library yet. there was a series of posts by MikeDB over the past few days that discusses the issues.

    if you want Uni-directional, then the I2S master/slave will do quite nicely over short distances - as it needs multiple signals.

    over longer distances the DS90UA101 serialiser / deserialiser allows all the I2s signals to be carried on a single twisted pair.

    serial can work, probably using RS485 as a physical layer, as the teensy so can sustain 3Mbits or more. however, the audio library does not have a widget for this.

    I hope this helps your thinking.

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