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Thread: OctoWS2811 pixel corruption with dim brightness values

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    Aug 2013
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    OctoWS2811 pixel corruption with dim brightness values

    I'm having problems with OctoWS2811 with specific low-intensity bit patterns when we have multiple Teensy3's connected to the same machine. The conditions seem somewhat specific and hard to pinpoint: with only one teensy on my laptop it is ok, but fails when there are multiple teensys, and on the BeagleBone Black it fails with even just one teensy connected. It is repeatable across the four boards that I have here. The Teensy's are running stock VideoDisplay firmware and are being powered by the external 5V@20A regulated supply and are not having any power issues.

    The two attached patterns for our LED strips differ in a single bit, but turning on that bit in pixel 0 on strip #4 causes all of the later pixels on all eight strips to be incorrect. The problem only appears to occur when the intensity on the adjacent strips are less than or equal to 7, which means that only the last three bits in each word are set.

    You should be able to cat good-pattern.bin > /dev/ttyACM1 to see the YGR diagonals and then cat bad-pattern.bin > /dev/ttyACM1 to see the bug. Instead of a uniform dim diagonal, what we get is something like this with intense blues and other colors:


    Bad LED checkerboard test pattern by hudson, on Flickr
    http://www.flickr.com/photos/osr/9484997647/

    I've also observed with this setup that drawing anything on strip #4 causes frequent USB failures on the BBB. Masking all of the sliced pixel data with 0xF7 to exclude seems to prevent this from happening (as well as preventing the color bug). Has anyone seen either of these before?
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