worldsemi,ws2812-gpio

Vendor: Worldsemi Co., Limited

Description

Worldsemi WS2812 LED strip, GPIO binding

Driver bindings for bit-banging a WS2812 or compatible LED strip.

The CPU driver uses inline assembly, and isn't available for all
boards. The timing is automatically derived from the CPU clock frequency,
or can be provided by setting the delay-txx properties in the device
tree, or can be manually provided by the Kconfig settings DELAY_Txx.

The four delays provided (calculated based on the clock frequency,
provided by a dts, or Kconfig file) determine the delays as depicted
below. The exact timings of the LED strip data line might vary on the
type of LEDs used, consult the data-sheet for the precise timings.

0 code
   +-------+                 +---
   |       |                 |
   |  T0H  |       T0L       |
   |       |                 |
---+       +-----------------+

1 code
   +---------------+         +---
   |               |         |
   |      T1H      |   T1L   |
   |               |         |
---+               +---------+


Example dts file:
/ {
      cpus {
          cpu@0 {
              clock-frequency = <64000000>;
          };
      };

      rgb_led: ws2812 {
          compatible = "worldsemi,ws2812-gpio";
          chain-length = <1>;
          color-mapping = <LED_COLOR_ID_GREEN
                           LED_COLOR_ID_RED
                           LED_COLOR_ID_BLUE>;
          gpios = <&gpio0 16 0>;
      };
};

Example dts file:
/ {
      chosen {
          zephyr,led-strip = &rgb_led;
      };

      rgb_led: ws2812 {
          compatible = "worldsemi,ws2812-gpio";
          chain-length = <1>;
          color-mapping = <LED_COLOR_ID_GREEN
                           LED_COLOR_ID_RED
                           LED_COLOR_ID_BLUE>;
          reset-delay = <50>;
          gpios = <&gpio0 16 0>;
          delay-t1h = <48>;
          delay-t1l = <32>;
          delay-t0h = <16>;
          delay-t0l = <32>;
      };
};

Properties

Properties not inherited from the base binding file.

Name

Type

Details

chain-length

int

 
The number of devices in the daisy-chain.

This property is required.

color-mapping

array

 
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>;

This property is required.

reset-delay

int

 
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.

Default value: 8

gpios

phandle-array

 
GPIO phandle and specifier for the pin connected to the
led-strip. Exactly one pin should be given.

This property is required.

delay-t1h

int

 
Number of NOP assembly operations to create a delay for a 1 bit, high
voltage period (default 700 nsec)

delay-t1l

int

 
Number of NOP assembly operations to create a delay for a 1 bit, low
voltage period (default 600 nsec)

delay-t0h

int

 
Number of NOP assembly operations to create a delay for a 0 bit, high
voltage period (default 350 nsec)

delay-t0l

int

 
Number of NOP assembly operations to create a delay for a 0 bit, low
voltage period (default 800 nsec)