1 -------------------------------------------------------------------------------
3 -------------------------------------------------------------------------------
5 This is a capture of data output to 4 LED universes of 256 RGB LEDs.
6 Every universe has a frame size of 768 bytes and the dumps are clocked at
7 roughly 100 frames per second.
10 - Koen Kooi's evil vendor tree: https://github.com/koenkooi/kernel
11 - PRU WS28xx firmware: https://github.com/mranostay/ws28xx-lighting-pru
12 - WS2812B datasheet: http://www.adafruit.com/datasheets/WS2812.pdf
15 WS2812B protocol overview
16 -------------------------
18 All values have a +/- tolerance of 150 nanoseconds so the PRU firmware uses
19 the slightly different timing values below to sync the high/low transitions.
21 Logic low -> high 0.40 uS -> low 0.85 uS (1.25 uS)
22 Logic high -> high 0.80 uS -> low 0.45 uS (1.25 uS)
25 Each LED receives and then stores the first 24-bits of GRB ordered data then
26 passes any more out the Data Output pin to the next LED in the chain.
28 This functions as a "reverse" shift register and allows the strip length not
29 to be defined in the protocol.
35 The logic analyzer used was a Saleae Logic16 (at 5MHz):
37 Probe WS2812B LED strip
38 -----------------------------
42 4 (orange) Universe #4
48 The data contains various RGB values and frames.
50 The sigrok command line used was:
52 sigrok-cli --driver saleae-logic16 --samples 10M --config samplerate=5mhz \
53 -p 0=UNI1,1=UNI2,2=UNI3,3=UNI4 -o ws281x_4ch_5mhz.sr