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Thread: Teensy 3.0 - Dead, but at the same time not dead.

  1. #1
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    Teensy 3.0 - Dead, but at the same time not dead.

    I've got a pair of 3.0's that I just got for a programmable POV glow poi set I'm making with the octows2811 library and a strand of ws2811's. Everything was going great, got all the test programs working and started messing around with the code, but at some point the 3.0 just stopped updating the LED's properly, and now when the data pin is connected they will flash white, then quickly fade to red, and be unresponsive to reprogramming/reset. I checked all the power pins and it seems to be working fine, I don't have a oscilloscope to check the data, but from the fact they still work, I'm going to say it's probably not them.

    So after messing around with it, I think it is something to do with the reprogramming, I tried loading up blink, and it does not work. In the verbose window it reacts to the reset button, says '01:47:37: remote cmd: "status" 01:47:37: status data sent' when uploading from arduino. but no response form the board itself.

    I cut the trace between VUSB and VIN, and had it hooked up to an external power supply in the form of a 3.7V 5600mah lipo, going through a booster to 5V. Once I started having problems, I switched to a computer power supply 5V pin on a plug, no change in behavior.

    I don't know what else to try.

    Also, a question about my project. Since I'm only running 10-20 LED's at a time, is it possible to run the leds off VUSB by itself? is there any way to dim the leds without pulse width modulation, since that really distracts from the POV aspect of the poi...?

    Thanks a ton for any help you can offer in advance, I'm stumped, and I got to have these guys done by wakarusa!!

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by toastyman View Post
    I don't know what else to try.
    Perhaps try the recovery process (holding the reset button while plugging in the USB cable). Details are here:

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

    Also, a question about my project. Since I'm only running 10-20 LED's at a time, is it possible to run the leds off VUSB by itself?
    Most USB ports on computers and powered hubs can deliver 500 mA of current.

    If you have a long USB cable, the size of the power conductors can matter. The 4 foot cables PJRC sells have #24 wire, but many other cables on the market have #28 or even #30 wire, which will drop too much voltage if you run 0.5 amp over a substantial distance. Those thin cables work great for portable devices that like camers that do not charge over the USB, but they're not great for electronic projects needing more current. That's why we had cables made with #24 power wires.

    The RGB LED uses about 15 mA per color, but the actual current isn't precise. Generally 50 mA per LED (when fully white) is a good power budget. The Teensy 3.0 needs about 27 mA. So 9 LEDs plus the Teensy 3.0 adds up to 477 mA, just under the 500 mA limit.

    Most computers will allow you to use a bit more than 500, but going over the limit risks triggering the current limiting protection in your PC. Apple Macs have the best, most precise and fastest response overcurrent circuitry. Most of the times I've heard people triggering these limits, it's on a Mac. Some cheap PCs don't have any limiting, even though it's required by the USB spec and safety standards. The power supplies in many desktop PCs can produce an incredible amount of current at 5 volts, though how well they work when the ratio of power on 12 and 5 volts is outside the expected range can be, well, unpredictable. Be careful drawing lots of power from a cheap PC.

    Also, unpowered hubs can usually only provide 100 mA. The idea is they get 500 mA from the PC, use up to 100 mA for themselves, and each of the 4 downstream ports can get 100 mA. Often they have transistors or current protection that limits you to 100 mA.

    USB hubs are very cheaply made consumer devices. Typically the powered ones can provide 500 mA, but not on all the ports simultaneously. Beware pushing a cheap hub to its power limit on all ports at the same time. Often the limit is the supplied power adaptor, which can't even output enough current. For example, I have a 7 port hub on my desk which came with a power adaptor rated for 2.6 amps max.


    is there any way to dim the leds without pulse width modulation, since that really distracts from the POV aspect of the poi...?
    The WS2811 has no configuration options. However, its internal PWM is really fast. I'm surprised this is an issue?
    Last edited by PaulStoffregen; 05-04-2013 at 06:27 PM.

  3. #3
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    OK, So I got blink to work, (program issue, not board) but now when I load up any octoWS2811 test programs, on any pin I get all full brightness white LED's. I cut the strip down to 4 LED's so powering from the USB would not be a problem. I performed the reset procedure, and it did not effect the behavior... any idea what I can try from here?

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