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WS2812 Sample Application

Overview

This sample application demonstrates basic usage of the WS2812 LED strip driver, for controlling LED strips using WS2812, WS2812b, SK6812, and compatible driver chips.

Requirements

  • LED strip using WS2812 or compatible, such as the NeoPixel Ring 12 from AdaFruit.

  • Note that 5V communications may require a level translator, such as the 74AHCT125.

  • LED power strip supply. It’s fine to power the LED strip off of your board’s IO voltage level even if that’s below 5V; the LEDs will simply be dimmer in this case.

Wiring

  1. Ensure your Zephyr board, and the LED strip share a common ground.

  2. Connect the LED strip control pin (either SPI MOSI or GPIO) from your board to the data input pin of the first WS2812 IC in the strip.

  3. Power the LED strip at an I/O level compatible with the control pin signals.

Building and Running

This sample’s source directory is samples/drivers/led_ws2812/.

To make sure the sample is set up properly for building, you must:

  • select the correct WS2812 driver backend for your SoC. This currently should be CONFIG_WS2812_STRIP_SPI unless you are using an nRF51 SoC, in which case it will be CONFIG_WS2812_STRIP_GPIO.

  • create a led-strip devicetree alias, which refers to a node in your devicetree with a worldsemi,ws2812-spi or worldsemi,ws2812-gpio compatible. The node must be properly configured for the driver backend (SPI or GPIO) and daisy chain length (number of WS2812 chips).

For example devicetree configurations for each compatible, see samples/drivers/led_ws2812/boards/nrf52_pca10040.overlay and samples/drivers/led_ws2812/boards/nrf51_pca10028.overlay.

Some boards are already supported out of the box; see the boards directory for this sample for details.

Then build and flash the application:

west build -b <board> samples/drivers/led_ws2812
west flash

When you connect to your board’s serial console, you should see the following output:

***** Booting Zephyr OS build v2.1.0-rc1-191-gd2466cdaf045 *****
[00:00:00.005,920] <inf> main: Found LED strip device WS2812
[00:00:00.005,950] <inf> main: Displaying pattern on strip