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Thread: Feasible to drive Adafruit Neopixel LED strip?

  1. #1
    Junior Member
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    Feasible to drive Adafruit Neopixel LED strip?

    Adafruit is kind of scary about controlling their new "Neopixel" 60-led strip due to stringent timing rqts. they write

    "to get high density, the controller chip is inside the LED, which is kind of cool, but also means that the chip only uses a single pin for input and a single pin for output. The protocol used is very very timing-specific and can only be controlled by microcontrollers with highly repeatable 100nS timing precision. We have example code for using with the Arduino Uno/Mega microcontroller at 8MHz and 16MHz, but it will not work with the Raspberry Pi, Basic Stamp, NETduino, any other interpreted/virtual machine microprocessor or any processor slower than 8 MHz."

    The above is from this page http://adafruit.com/products/1138

    So is this controllable using the Teensy 3.0? Seems to me it should be possible to avoid timing problems by masking interrupts. Suggestions?

    thanks in advance.
    Charlie in Encinitas CA

  2. #2
    Senior Member PaulStoffregen's Avatar
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    I believe these are the WS2811 chip. Please see this topic:

    http://forum.pjrc.com/threads/15620-...PI_LED-library

    My understanding is today there isn't a viable solution for WS2811 chips on Teensy 3.0. I know Daniel is planning to add it to his FastSPI_LED library.

    I've also got something special planned for WS2811 applications....... (I'll post about it on that other topic, so please discuss over there)

  3. #3
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    Yes, you can run NeoPixels, but ...

    I've had some success running NeoPixels with the Teensy, but I still don't have it perfected and it's been a very frustrating path. The main problem seems to be the 3.3V signaling from the Teensy 3.0/3.1, so I added a level converter I got from SparkFun.com. That almost worked. But the system was still hinkey, so I put the scope on it. The signal I was getting from the Teensy looked perfect, but after it passed through the level converter, I had a wave form that looked like a square wave with the top slanting steeply from the front to back. I also noticed that the output of the converter never got above 4.4VDC. I eventually deduced that the mosfets in the level converter were simply too slow.

    After some research, I discovered that some other people have had success using the SN74HCT245 as a one-way level converter that gives nice clean square waves at five volts for the output. I've ordered some today, should have them next week. I'll try to remember to update this post with the results.

    Ray

  4. #4
    Senior Member+ MichaelMeissner's Avatar
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    PJRC now has the following carrier that includes the SN74HCT245 and has the wiring to use the Octows2811 library, using 2 cat6 cables to get to the lights: http://www.pjrc.com/store/octo28_adaptor.html.

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