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Thread: Teensy 3.2 "Uknown USB Device"

  1. #1
    Junior Member
    Join Date
    May 2020

    Teensy 3.2 "Uknown USB Device"

    I have a Teensy 3.2 that is mounted on a custom PCB. I have been programming and using it without problem for weeks until today. When I powered it on today, the program didn't run. I attempted to re-upload the code by connecting it to my laptop, but when I plugged in the usb, I got an error message saying that the last device that was connected had malfunctioned and was not recognized by the computer. I tried using the push-button to force the Teensy into programming mode, but the same problem occurs after I release the button.

    I tried checking the response in Teensy Loader as mentioned in other threads by closing the Arduino IDE, disabling the auto feature, and pushing the button on the Teensy, but there was no response.
    With the board plugged into the usb, I checked the voltage at the Vin and 3.3V and they were both where they should be (5.01V and 3.28V respectively). The program pin holds a steady 3.3V and drops to 0V when the button is pressed.
    I have tried reinstalling the device drivers to no avail.
    I tried multiple cables and none solved the problem.

    Is the board bricked?

    Any help is much appreciated!

  2. #2
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    Doesn't sound good. Is this on Windows #?

    Only thing I would try is with best known cable - unplugged:
    > Do a verify of known good blink sketch for T_3.2
    > Press the Button
    > Plug the cable into the computer on a different USB port
    > Release the Button

    That should make sure the Teensy comes up clean and the computer sees only what it presents without history on the port

  3. #3
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    The fact that your PC is detecting something is still a good sign.

    Try holding the button down while you plug in the USB cable. This prevents any "bad" code on the Teensy from running. Details here:

    As a final last resort, cold reboot (complete power off) your PC. Then do this button hold while plugging in the cable.

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