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Thread: Plugged teensy 2.0 into USB while powered by 5v, can't upload new program

  1. #1
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    Plugged teensy 2.0 into USB while powered by 5v, can't upload new program

    I am working on a sculpture in Austin for the fun fun fun Fest and I just messed up my teensy 2.0. It was running an LED strip and I forgot to remove it from power before I plugged the USB into to upload a new program.
    When I plug it into USB now the on board LED lights up and pulses so I know it is getting power and running, but when I press the reset button to upload a new program it can't find the teensy and the lights go off.
    Is there anyway I can upload a program without using USB? Or is there anyone in Austin who can lend me a teensy 2.0? I need it tonight
    Please help

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by Mrichard View Post
    When I plug it into USB now the on board LED lights up and pulses so I know it is getting power and running, but when I press the reset button to upload a new program it can't find the teensy and the lights go off.
    That sounds like the Teensy side is working. It's running your old code. When you press the button, it stops running your program. It's probably running the bootloader, waiting for you to upload new code.

    This page has a couple more things to try.

    http://www.pjrc.com/teensy/troubleshoot.html

  3. #3
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    I have two teensy 3.0's that behave in a similar way and three that dont. For the ones that do, I find that if I cut the 5v supply to the teensy (leaving the USB connected) and then press the button shortly after reconnecting power, it always works. What's odd is that for a while, it will continue to work as expected, but after a while it stops registering the button press again. I also use the command line teensy loader and see the same behavior there.

    I figured it was something to do with my sketch until it became clear that some teensies were doing it and others weren't. If I stop running them off of external power (e.g. reconnect VIN to VUSB), they all work correctly.

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by tetsuo View Post
    If I stop running them off of external power (e.g. reconnect VIN to VUSB), they all work correctly.
    Can you tell us a bit more about this power supply?

    Aside from the obvious question of whether the power is stable, I'd look at possible ground issues. If it's earth grounded, and your PC is too, perhaps there's some voltage between the 2 different grounds, causing unexpected current to flow through the Teensy and the USB cable's ground. Those types of problems are called "ground loops" and they're tricky to troubleshoot. One quick test involves simply measuring the voltage between the 2 grounds, while they're not connected to Teensy. Ideally you should see zero volts. Use both DC and AC. Often these problems show up as AC voltages.

    Edit: on the boards that are working, I would be concerned that whatever problem is happening is affecting them too, but they're just barely able to operate.

  5. #5
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    It happened w/ multiple power supplies. A cheap wall wart, a decent ebay PSU, and a fancy MeanWell. I run all of my teensies off of USB power at the moment (4 teensies and 6 power supplies in the mix, so lots of potential for grounding issues), and haven't seen this behavior anymore as a result.

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