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Thread: I bricked not one but two teensy 4.1s by uploading Blink to them

  1. #1

    I bricked not one but two teensy 4.1s by uploading Blink to them

    I'm at a total loss here. My 3.6 works just fine. Both 4.1s are experiencing the exact same issue as far as I can tell.

    I can only upload a sketch to them by pressing the program button. As soon as I do, the red light turns on at half brightness, then full, then off, and then nothing and the board is invisible to my computer. Won't even blink. Unplugging it won't play the Windows USB disconnect sound so that means it's gone before windows finished playing the connected sound.

    No other sketch works either. That was the problem with the first, it suddenly wouldn't work in the project I've had it sitting in for months. Second one was brand new, hadn't even opened the packaging. Was blinking by default just fine until I uploaded blink. I'm even on fresh windows installation right now, by a few hours. What gives?

  2. #2
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    Quote Originally Posted by Eli_Beeblebrox View Post
    What gives?
    Very difficult to say why it's not working for you. It definitely does work when I test here.

    First, check the simple things. Make sure you're using the latest software, which is version 1.54. To check, click Help > About in Arduino.

    Version 1.54 did fix a startup bug. I've never seen that bug hit the LED blink program, but if you have 1.53 or older, installing the latest is so simple, so try that first.

    Another problem we sometimes see are (usually silently) corrupted installs because Windows Defender or some other lame anti-virus software interfered with installing some file. Just quitting Arduino, running the 1.54 installer and restarting Arduino might fix everything. Or if this is a case of anti-virus messing up the install, it might do the same thing again (but many anti-virus bugs often silently vanish a few days later when the vendor updates). You might need to temporarily disable it. The Teensyduino installer doesn't use any network access, so you can unplug from the internet while anti-virus is off and the installer will be able to work without the internet.

    The next thing to try is the 15 sec restore. Hold the Program button until you see a quick flash of the red LED, then release. This will cause a complete wipe of the flash memory and restore of the known-good LED blink. The process takes about a minute. You'll know it's done when the red LED turns off and the orange LED starts blinking. Your PC should detect the board and it should appear in the Tools > Ports menu as RawHID (not Serial). While this won't solve anything happening on your PC, it can at least give you confidence the Teensy 4.1 board is still working properly.

    If it's still not working, there's a chance perhaps your PC is creating a bad .HEX file. That's pretty unlikely. But to test this, you could find the HEX file Arduino creates. It's in a hidden temporary folder. Click File > Preferences to turn on verbose output while compiling, and then look at the pathnames in the huge amount of info Arduino shows. The .ELF file also has useful info, so if you'd like us to try running that compiled code on a Teensy 4.1, just put the .HEX and .ELF into a ZIP file and upload it here. If using "Quick Reply", click "Go Advanaced" to get to the forum's editor which lets you attach a file to your message. Then I (and maybe others) can try running the same .HEX file on our Teensy 4.1 boards to see if it does the same thing.

  3. #3
    Senior Member
    Join Date
    Feb 2016
    If you run linux I find teensy_loader ( on a raspberry pi works well. download, unzip, copy to linux machine,type "make", copy binary to suitable location (sudo cp teensy_loader_cli /usr/local/bin) then run command
    sudo teensy_loader_cli --mcu TEENSY41 -v -w -s Blink.ino.TEENSY41.hex
    My blink is 500ms so you can see the difference between the default one.h

    Another option anyway to rule out any windows software issues.

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