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Thread: Alternative I2S RX/TX pinout for audio-shield-like board

  1. #1
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    Alternative I2S RX/TX pinout for audio-shield-like board

    Hello folks,

    I'm working on a new board based on the Audio Shield design and it'd be more handy for me to route RX and TX (for I2S communication) via pins 15 and 14 (on Teensy 4.0) instead of 7 and 8. So I was wondering whether there's an easy way (or if it's even possible) to configure the Audio Library to use the alternative pinout when talking to the audio codec, instead of the default pin assignment.

    Thanks!

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by meronym View Post
    Hello folks,

    I'm working on a new board based on the Audio Shield design and it'd be more handy for me to route RX and TX (for I2S communication) via pins 15 and 14 (on Teensy 4.0) instead of 7 and 8. So I was wondering whether there's an easy way (or if it's even possible) to configure the Audio Library to use the alternative pinout when talking to the audio codec, instead of the default pin assignment.

    Thanks!
    I don't think that is possible on the Teensy 4.0/4.1. The I2S port #1 has 5 pins that can act as input or output ports, plus the 3 clocking pins:
    • Pin 6 -- OUT1D
    • Pin 7 -- OUT1A
    • Pin 8 -- IN1
    • Pin 9 -- OUT1C
    • Pin 20 -- LRCLK1
    • Pin 21 -- BCLK1
    • Pin 23 -- MCLK1
    • Pin 32 -- OUT1B


    On the Teensy 4.0, pin 32 (OUT1B) is on a solder pad underneath the Teensy.

    To change the meaning of the pins whould likely take a deep dive into the hardware reference manual to change settings.

    But the pin-out card for the Teensy 4.1 lists that:
    • Pin 39 is an alternate pin for OUT1A
    • Pin 38 is an alternate pin for IN1


    That means there might be a way to use pins 38/39 instead of 7/8. Note, these pins are not brought out in the Teensy 4.0.

    The other possibility on the Teensy 4.1 is to switch to the second I2S device. The second I2S device does not have options in the input/output pins like I2S1, but it uses a completely different set of pins:
    • Pin 2 -- OUT2
    • Pin 3 -- LRCLK2
    • Pin 4 -- BCLK2
    • Pin 5 -- IN2
    • Pin 33 -- MCLK2


    On the Teensy 3.2, 3.5, and 3.6, I believe all of the audio pins are fixed. In fact two of them overlap with the SPI pins, and you have to use the alternate SPI pins when you have the revision C audio shield installed.
    Last edited by MichaelMeissner; 06-10-2021 at 09:02 PM.

  3. #3
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    This was helpful, thank you!

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