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Thread: Digital noise issues on a simple board

  1. #1
    Junior Member
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    Jul 2022
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    Digital noise issues on a simple board

    Hi,

    I am developing a prototyping board that's designed mainly for Teensy and Daisy Seed. The board produces aggressive digital noise on Teensy (4.1, MQS/PT8211) but not on Daisy.

    Since I'm not an engineer I immidiately blamed my PCB design. But then, the Daisy isn't producing any noise, so I'm not sure how to move forward.

    PCB design (screenshot below)
    The PCB doesn't have any components on it (no filters, passive or active parts). Both sides have ground planes, stitched together. There are 80 multipurpose footprints that can take either a pot, switch or jack socket. GND and VCC have dedicated pads for patching the corresponding pins of the Teensy/Daisy.

    My thinking was to make it similar to a breadboard. If additional components are needed, I could add them on a little perfboard I've placed on the bottom right side of the PCB.

    What I've tried
    Using digital filtering
    Using caps on the MQS output and on the 3v3 line

    I've noticed that if the audio library isn't initialized the noise stops.

    Questions:
    Is there a way to solve this without adding RC filters on each ADC? Just by modifying the PCB design?
    Is there a reason why the Teensy produces noise, but Daisy isn't?
    If I need to add passive/active circuits, what's the simplest solution, considering I'm not going for high-end sound quality but rather simplicity and practicallity?

    Thank you
    Roey

    ---

    Here's a link to the PCB design
    https://tsemah.notion.site/Simple-PC...5343a04bb8ea74
    Last edited by Roey; 07-02-2022 at 08:43 PM.

  2. #2
    Junior Member
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    Jul 2022
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    Update:

    Tried with an old Teensy 3.2 - works fine. No digital noise at all.
    Tried the PT8211 on Teensy 4.1 - same noise issues as with MQS.

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