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Thread: teensy audio pc layout

  1. #1
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    teensy audio pc layout

    Hi all
    I have just finished a guitar amp project with teensy 3.6 + audio. Fairly happy but am considering respinning a pcb i had made onto which i mounted everything. I have a couple of questions re layout.
    1. Is it better to stack teensy and audio shield or have them side by side? Shield on top of teensy of vice versa?
    2. How to design ground plane decoupling of my PCB?
    3. Should I put a separate 3.3v regulator for the audio assuming non stacked.
    4. Any other general advice of achieving best noise performance?
    Regards
    Richard

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    In doing the Teensy 4.0/4.1, Paul has mentioned several times that it is important that the wires to the audio shield be as short as possible. In addition, revision C of the audio shield added a 100 ohm resistor in the data path for MCLK. If you are mounting it side by side, and you have a revision B board, it might make sense to add the resistor. Evidently the resistor is needed for the higher speed Teensy 4.0. I don't know if the Teensy 3.6 might need it also, particularly if you overclock it.

    So I suspect the best method is to put the Teensy 3.6 on the bottom, and mount the audio shield directly on top of the Teensy. That way you can get to the SD card easily if you need it. You can mount underneath, but it may interfere with attaching things to the audio shield, and the back 1" of the Teensy won't be supported.

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    Hi
    Thanks for the reply. My existing design used the 3.6 and its soldered in so need something new. Probably a 4.0 I guess. I don't need Sd card. I will use the teensy audio line in and out headers so no other shield connections needed. If stacked would be a bit easier to have teensy 4.0 on the shield and that on my base board. If not stacked I have the chance to separate the power and grounds better if needed. I have been reading about not sharing the ground return for digital and analogue and having separate supplies.

  4. #4
    Senior Member houtson's Avatar
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    Hi, you might want to check out https://codeberg.org/dcoredump/TeensyMIDIAudio from user @C0d3man for a few ideas

  5. #5
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by richardlane View Post
    Hi
    Thanks for the reply. My existing design used the 3.6 and its soldered in so need something new. Probably a 4.0 I guess. I don't need Sd card. I will use the teensy audio line in and out headers so no other shield connections needed. If stacked would be a bit easier to have teensy 4.0 on the shield and that on my base board. If not stacked I have the chance to separate the power and grounds better if needed. I have been reading about not sharing the ground return for digital and analogue and having separate supplies.
    Note, that Teensy 4.0/4.1 have different pinouts for the Audio shield than the Teensy 3.1/3.2/3.5/3.6 did. Thus you need revision D for Teensy 4.0/4.1 and revision C for the 3.x. So, you likely would need to change your code for other connections as well.

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    Quote Originally Posted by richardlane View Post
    Hi
    Thanks for the reply. My existing design used the 3.6 and its soldered in so need something new. Probably a 4.0 I guess. I don't need Sd card. I will use the teensy audio line in and out headers so no other shield connections needed. If stacked would be a bit easier to have teensy 4.0 on the shield and that on my base board. If not stacked I have the chance to separate the power and grounds better if needed. I have been reading about not sharing the ground return for digital and analogue and having separate supplies.
    Richard:

    I recently completed my TeensyMIDIPolySynth project (https://forum.pjrc.com/threads/60690...l=1#post237404). I have had great luck with stacking the Teensy 4.x on top of the Rev D Audio Shield using 0.6" stacking headers on the Teensy 4.x & corresponding sockets on the Audio Shield. In my early prototype, I put the Teensy 4.x on the bottom, but that made it extremely difficult to press the programming button if/when needed. Also, with the current stack, I have had no problem inserting and/or removing the SD card using the socket on the Audio Shield. YMMV !!

    Good luck & have fun !!

    Mark J Culross
    KD5RXT

  7. #7
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    As for ground plane design, the basic tenets of mixed signal ground plane design are well-covered in this app note from Analog Devices.

    https://www.analog.com/en/analog-dia...-grounded.html

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