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Thread: UnoWS2811? DuoWS2811?

  1. #1
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    UnoWS2811? DuoWS2811?

    Hi friends (mostly hi Paul),

    I'm using OctoWS2811 to drive a single (though perhaps I'll want two) strip of WS2811s controlling LEDs.

    Is there a way to modify the library to only try to control 1 or 2 strips instead of all 8? I read through the source and it didn't seem obvious. The pins weren't referred to anywhere except setting them to output mode? I'd ideally like to save ram & pins & time spent copying / DMAing.

    Ian

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by ianloic View Post
    Is there a way to modify the library to only try to control 1 or 2 strips instead of all 8?
    The FastSPI_LED and NeoPixel libraries do this. But they use CPU-hogging bit-bashing, not efficient DMA, so they're useful for short to modest length strips.

  3. #3
    Senior Member PaulStoffregen's Avatar
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    And no, there isn't any realistic way to modify OctoWS2811 for only a single strip. The DMA's minimum transfer size is 8 bits. If you want fewer than 8 outputs, you have to waste those unused bits of RAM to use DMA.

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    Quote Originally Posted by PaulStoffregen View Post
    The FastSPI_LED and NeoPixel libraries do this. But they use CPU-hogging bit-bashing, not efficient DMA, so they're useful for short to modest length strips.
    Yeah - I definitely want to use the DMA approach. Thanks!

    Ian

  5. #5
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    Ian, did you make changes to the library?

    I need three strips at most (about 300 to 400 LEDs total) and would be very much interested to free up some pins for other peripherals.

  6. #6
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    Quote Originally Posted by jitter View Post
    Ian, did you make changes to the library?

    I need three strips at most (about 300 to 400 LEDs total) and would be very much interested to free up some pins for other peripherals.
    Nah, I didn't need to use any other pins so I just left some unused.

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