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Thread: PC communication problems with Teensy 3.0

  1. #1
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    PC communication problems with Teensy 3.0

    I've got an intermittent problem which happens frequently and is making my head hurt. I'm working on LED lighting for a robot participating in the FIRST competition. Our first match is tomorrow. I'm using a Teensy 3.0 to control an AdaFruit NeoPixel string of 160 RGB LEDs. First thing I figured out is that you can't run the AdaFruit strandtest sketch successfully unless you keep the Teensy at 96MHz. (That's the default setting in the Arduino IDE.) But what is driving me crazy is that I can run the Teensy blink sketch w/o problems, but when I run any NeoPixel sketch, there is a high probability that it will mess up the USB port on the PC, making the Serial Monitor unavailable. I often have to reboot if I want to connect to the Teensy using the USB port. I've got a 100 Ohm resistor on the data line to the LED strand in order to reduce ringing, and I've got a 1000uF cap across power and ground. When things work, they work beautifully, but the problems are so frequent they are maddening and seriously threatening my ability to get this project completed on time. (Some time today.)

    Even if I don't get this done today, I plan to keep working on it. Tomorrow is just the first of three matches we have, so if you have an idea what might be happening, please speak up, even if it's after 3/13/2014.

    On the sketch that we use on the robot, we do use the Serial Monitor for both debugging messages and to send commands to the Teensy. I thought that might be part of the problem, but we still lose the USB port even when just running strandtest.

    Thanks for your help.
    Ray

  2. #2
    Senior Member xxxajk's Avatar
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    Just a guess here, but 1000uF might be a bit on the high side, and could look like a short-circuit to the PC's USB power. I'd try a different value.
    Try 270uF. It also doesn't hurt to add a 1M bleeding resistor across that capacitor.

    Hope I helped.

  3. #3
    Senior Member PaulStoffregen's Avatar
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    Wow, 160 is a lot of LEDs. What's providing the power for all those LEDs? Not just the USB cable, I hope. Usually about 9 or 10 (if they ever turn on fully) is the most you run reliably connect to a USB powered product.

  4. #4
    Senior Member xxxajk's Avatar
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    I was thinking the same thing.

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    Quote Originally Posted by PaulStoffregen View Post
    Wow, 160 is a lot of LEDs. What's providing the power for all those LEDs? Not just the USB cable, I hope. Usually about 9 or 10 (if they ever turn on fully) is the most you run reliably connect to a USB powered product.
    The power is provided by a separate source, a bench power supply during testing and the robot's main battery when the lights are on the robot. The matches are only 3 minutes long.

    Ray

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