-------------------------------------------------------------------------------
WS2812B LED strip
-------------------------------------------------------------------------------

This is a capture of data output to 4 LED universes of 256 RGB LEDs.
Every universe has a frame size of 768 bytes and the dumps are clocked at
roughly 100 frames per second.

Details:
 - Koen Kooi's evil vendor tree: https://github.com/koenkooi/kernel
 - PRU WS281x firmware: https://github.com/mranostay/ws28xx-lighting-pru
 - WS2812B datasheet: http://www.adafruit.com/datasheets/WS2812.pdf


WS2812B protocol overview
-------------------------

All values have +/- tolerance of 150 nanoseconds so the PRU firmware uses
slightly different timing value below to sync the high/low transitions.

  Logic low  -> high 0.40 uS -> low 0.85 uS (1.25 uS)
  Logic high -> high 0.80 uS -> low 0.45 uS (1.25 uS)
  Latch      -> low 50 uS

Each LED receives and the stores the first 24-bits of GRB ordered data then
passes any more out the Data Output pin to the next LED in the chain.

This functions as a "reverse" shift register and allows the strip length not to
be defined in the protocol.


Logic analyzer setup
--------------------

The logic analzyer used was a Saleae Logic16 (at 5MHz).

  Probe       WS2812B LED strip
  -----------------------------
  1 (black)   Universe #1
  2 (brown)   Universe #2
  3 (red)     Universe #3
  4 (orange)  Universe #4


Data
----

The data contains various RGB values and frames.

The sigrok command line used was:

  sigrok-cli --driver saleae-logic16 --samples 10M --config samplerate=5mhz \
             -p 0=UNI1,1=UNI2,2=UNI3,3=UNI4 -o ws281x_4ch_5mhz.sr