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-------------------------------------------------------------------------------
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 WS28xx firmware: https://github.com/mranostay/ws28xx-lighting-pru
- WS2812B datasheet: http://www.adafruit.com/datasheets/WS2812.pdf
WS2812B protocol overview
-------------------------
All values have a +/- tolerance of 150 nanoseconds so the PRU firmware uses
the slightly different timing values 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 then 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 analyzer 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
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