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Thread: Problems using Teensy 4.0 Audio Lib and GUI

  1. #1
    Junior Member
    Join Date
    Sep 2019

    Problems using Teensy 4.0 Audio Lib and GUI

    I am having problems setting up a Teensy 4.0 with an audio shield
    to use the GUI software.
    This is what I have done in sequence:

    1. Downloaded the zip file for Arduino 1.8.10 - archived it
    2. Unzipped it and copy all of its contents intoan empty folder
    c:/Arduino 1.8.10/
    3. Dowwnloaded

    4. Executed the windows Teensyduino installer
    selecting the path c:/Arduino 1.8.10/
    and installed only the Audio library.

    I can run my own C
    code on the Teensy 4 do my own FFTs and receive
    the results on the serial monitor.

    5. Installed the Audio shield board
    (n.b. Rev B - requiring the 100ohm resistor)
    Connected the audio board according to the instructions :

    "Teensy 4.0 has its digital audio signals (MCLK, BCLK, LRCLK, TX, RX) in different locations.
    On Teensy 3.x, these are pins 11, 9, 23, 22, 13.
    On Teensy 4.0, those signals are pins 23, 21, 20, 7, 8.
    This audio shield will only work if wires are used to route those 5 signals.
    It does not work if soldered directly above or below a Teensy 4.0."

    n.b. I was unsure about the p.s. to the audio board from the Teensy
    so I connected Ground and 3V only (not 5V)

    6. Executed and transferred the code for a passthrough
    (and the correct object for the audio chip) into a sketch.
    Sketch compiles and downloads but nothing out of the headphones when
    audio signal injected.

    No output !

    I have a few questions and would be extremely pleased if you would answer them :

    A. Have i used the wrong revision of the audio board ?
    B. Is an Audio board available which will plug into a Teensy directly ?
    C. Are Teensy 4 and Audio boards available with legs ?
    D. Should I also connect the 5V from the Teensy to the Audio board ?
    E. Lastly is it possible to view the expansion of the output of the GUI
    system for the sketch as C code.

    Thank You, Brian Fish (UK)

  2. #2
    Senior Member+ MichaelMeissner's Avatar
    Join Date
    Nov 2012
    Ayer Massachussetts
    Yes, you have the audio shield designed for the Teensy 3.2, 3.5, and 3.6. There is a new version of the Audio Shield (revision D) that expects the pin layout of the Teensy 4.0. The PJRC page now has both boards:

    Using your existing board, one method is to plug both the Teensy and Audio Shield into a 1/2 size or larger breadboard at different locations. Then use jumper wires to connect from the Teensy 4 to the Audio Shield. Since you have the revision B board, you will need to also add a 100 ohm resistor on the wire connecting the Teensy 4.0 pin 23 to the MCLK on the Audio Shield. You do want to try and keep the wires as short as possible. Here is a pinout guide I posted previously going between the Teensy 4.0 and the Audio Shield:

    During the beta test, Paul made a limited series of Teensy 4.0 to Audio Shield converters that did this cross wiring. He has said there are no plans to make this into a product, but he did release the PCB design and BOM if you wanted to make your own converter:

    Finally, revision D of the board is now available (it was added recently). Whether the resellers in Europe or the UK have started selling this board, I don't know. At the moment, neither Adafruit or Sparkfun have picked it up in their catalogs. I imagine they will shortly be selling it, as will the European/UK distributors.

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