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Thread: Can't flash Teensy 4.0

  1. #1
    Junior Member
    Join Date
    Sep 2019

    Can't flash Teensy 4.0

    Hello there,
    So I recently ordered a new teensy and I can not upload any code to the teensy. I am trying the example program blink. I have soldered on my old audio shield to the teensy.
    On plugging the teensy in to a computer it is recognized in device manager as a raw HID device, the preshipped blink program runs. Pressing the reset button momentarily does not reset the blinking led on the teensy nor does it start programming when plugged in. On trying to flash(tried both a previously working teensyduino install and a fresh install of both arduino + teensy) it just gets stuck at waiting for device to reset/enter program mode. The onboard blink sketch freezes during this time as the blink sketch will freeze in its current state. Attached is a log
    1) plugged in
    2) tried to flash blink
    3) pressed program mode (nothing new in log)
    4) held reset for 15s

  2. #2
    Senior Member
    Join Date
    Jul 2014
    Quote Originally Posted by autouser View Post
    I have soldered on my old audio shield to the teensy.
    old audio shield does NOT work on Teensy 4, when soldered pin to pin.
    you need Audio board Version D for pin to pin compatibility with teensy 4.x

  3. #3
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    I'm trying to understand what you're describing with these words "Pressing the reset button momentarily does not reset the blinking led on the teensy nor does it start programming when plugged in."

    Would you do a quick test and tell me exactly what happens?

    Please unplug Teensy and reboot your computer. Do not run any programs after your PC boots up. The goal is to *not* run Arduino or Teensy Loader, so your computer will not do any communication with Teensy. The idea of this test is to just focus on what's happening with Teensy, without the extra complexity of what software on your PC might be doing.

    Then plug in Teensy. The orange LED should blink slowly, because it should be running the original program which is loaded during testing of the board at PJRC. The red LED (near the USB connector) should be off. Can you confirm if Teensy 4.0 looks this way?

    Press the pushbutton on your Teensy 4.0. Don't hold it down, just a quick press & release. What happens with the red and orange LEDs after you've pressed the button?

    Again, the idea here is to remove your PC's behavior from the equation, so we can just focus on what Teensy 4.0 is doing. That's why you should reboot and then make sure no software has started running.

  4. #4
    Junior Member
    Join Date
    Sep 2019
    I was removing everything off the board and all of a sudden it started programming again. I inspected the teensy before starting the removal of the audio shield and there were no obvious shorts or issues with soldering. After removing half the pins it magically started programming again. I put it all back together and im back to my project! Thanks for the help, I wish I knew what happened perhaps the heat from the iron or the extreme flexing of me trying to pry off the audio shield. Everything is working right now.

    I will make a new post but does anyone know if ws2812serial drives leds at 400khz or 800 and if its 400 how would I bump it up to 800khz?

  5. #5
    Junior Member
    Join Date
    Nov 2018
    I recently encountered the inability to flash as well (on a new Teensy 4.0 but guessing that's not the issue) after an abrupt Windows update & brownout. Paul: thanks for reminding me of this simple tip!

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