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Thread: Issues with diy Teensy 3.2 board

  1. #1
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    Issues with diy Teensy 3.2 board

    Hey, I'm having some issues getting a diy Teensy 3.2 board to get recognized by my PC. The parts are pulled from a new Teensy 3.2 that was flashed with a program beforehand. I've checked the power pins and they are all getting 3,3v. Reset_B is at ~3,3V.

    Tried scoping the usb lines ad I found alot of noise on D+(820mv) so I'm guessing that is the issue?

    Click image for larger version. 

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    Anyone have any suggestions on any other troubleshooting I could do? I'm thinking of cutting the traces for D+ and D- and soldering directly to the pins to see if I get rid of the noise but any other suggestions are welcome. It was measured while connected to a computer.

    Attached are schematic, front copper layer, back copper layer and both in same.

    Click image for larger version. 

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    There is probably alot of improvements that could be made to it, but fairly new to making layouts and it needed to be as small as possible.


    Edit;
    I had one board before this one that showed up as teensyduino_hid_raw when plugged in first time, however I wasnt able to program it, and after unplugging and plugging it back in it didnt show up anymore.

  2. #2
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    Some good info here. In your case, pay particular attention to the USB D+/D-.
    https://www.pjrc.com/store/ic_mkl02.html

    Vias in pads are a bad idea.

  3. #3
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    Yeah, thanks have skimmed through alot of it and got the same feedback from the pcb manufacturer :P. I guess I'll try to read through it more in detail and start working on a new version and try to avoid the common mistakes

  4. #4
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    Goddamn I'm stupid, started on a rough new layout trying to copy most of the layout from the original and noriced there were no caps on the crystal. Had originally switched to another one but pulled it form the teensy for this board. Anyways removed the 0,1uF caps from the crystal and now it atleast shows up as an unrecognized usb device. Will look into it some more tomorrow

  5. #5
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by pepsi View Post
    Reset_B is at ~3,3V.
    If you short the Program signal to GND (the same as holding the button on a Teensy 3.2), does the bootloader chip pull Reset low?

  6. #6
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by pepsi View Post
    Anyways removed the 0,1uF caps from the crystal
    Oh, yeah, that'll sure keep the crystal from oscillating. The schematic says you used 12 pF.

    The chip has built in capacitors which are configured for a crystal in the 8-10pF range. So unless you use a crystal rated for more, you probably should not add any capacitors.

  7. #7
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    Quote Originally Posted by PaulStoffregen View Post
    If you short the Program signal to GND (the same as holding the button on a Teensy 3.2), does the bootloader chip pull Reset low?
    Nope, hmmm

  8. #8
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    Quote Originally Posted by PaulStoffregen View Post
    Oh, yeah, that'll sure keep the crystal from oscillating. The schematic says you used 12 pF.

    The chip has built in capacitors which are configured for a crystal in the 8-10pF range. So unless you use a crystal rated for more, you probably should not add any capacitors.
    Yeah, stupid mistake on my part. removed them and not it shows up as unrecognized atleast
    Last edited by pepsi; 07-22-2021 at 04:26 PM.

  9. #9
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    Pretty sure I found the issue, wrong pin used for the reset button. Mine on the left Teensy 3.2 on the right. Doh, time to order new pcbs

    Click image for larger version. 

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    edit:
    nvm thats using the old bootloader chip, checked the updated schematic and looks good. Threw it in the ultrasonic to clean up the board will do more troubleshooting tomorrow i guess

  10. #10
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    Okay, so I had switched the labels on D+ and D-. I managed to flash a sketch to it, but when trying to flash a new one i just get the following error;
    Teensy did not respond to a USB-based request to enter program mode.
    Please press the PROGRAM MODE BUTTON on your Teensy to upload your sketch.
    So now I just gotta figure out why "pressing" my "button" doesent pull Reset_b low on the mcu

  11. #11
    Senior Member PaulStoffregen's Avatar
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    Maybe it's just the limited resolution of the images, but the PCB looks to have extremely small vias with close to zero annular ring. If that's really the case, even very slight drill misalignment may fail to make a connection between PCB layers.

    Before you make another PCB rev, seriously asking your PCB vendor about their design rules would be wise....

    Also ask them about "via in pad" process. Most PCB vendors offer this feature. Usually it costs quite a bit extra.

  12. #12
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    Hey, that is correct, I'll make them larger if I end up making another revision. Should definetely have given myself some more space to work with.

    Got one board working now, haven't tested if it's able to reset to programming mode since this one was able to reset via the usb command.

    Thanks for the feedback and fast answers

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