dts/bindings/led_strip/ws2812.yaml

# Copyright (c) 2019, Linaro Limited
# Copyright (c) 2019, Nordic Semiconductor ASA
#
# SPDX-License-Identifier: Apache-2.0

description: |
  Worldsemi WS2812 (and compatible) LED controller

  Driver bindings for daisy chains of WS2812 (and compatible devices
  like SK6812, or Everlight B1414) LED controllers.

  The PWM protocol is described here:
  https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/

  A 0 bit's pulse width is between 200 and 500 ns. A 1 bit's is
  at least 550 ns, with 700 ns or so typical. Pixel order is GRB.

  You can connect the device to either a GPIO on your SoC, or a SPI
  MOSI line. Use the worldsemi,ws2812-spi.yaml or
  worldsemi,ws2812-gpio.yaml bindings instead of this file after
  making your choice.

  Everlight B1414:

  The specification of the Everlight B1414 LED controller is slightly different.
  For the control signal (waveform) each bit is described with a 1.2 us pulse:

    0 bit: 300 ns high and 900 ns low.
    1 bit: 900 ns high and 300 ns low.

  There is a a +/- 80 ns tolerance for each timing.

  The latch/reset delay is 250 us and it must be set using the reset-delay
  property. The pixel order depends on the model and it can be configured
  using the color-mapping property.

properties:
  chain-length:
    type: int
    required: true
    description: |
      The number of devices in the daisy-chain.

  color-mapping:
    type: array
    required: true
    description: |
      Channel to color mapping (or pixel order).

      For example a GRB channel to color mapping would be

         color-mapping = <LED_COLOR_ID_GREEN
                          LED_COLOR_ID_RED
                          LED_COLOR_ID_BLUE>;

  reset-delay:
    type: int
    required: false
    default: 8
    description: |
      Minimum delay to wait (in microseconds) to make sure that the strip has
      latched the signal. If omitted, a default value of 8 microseconds is used.
      This default is good for the WS2812 controllers. Note that despite the
      WS2812 datasheet states that a 50 microseconds delay is required, it seems
      6 microseconds is enough. The default is set to 8 microseconds just to be
      safe.