led_ws2812

WS2812 Sample Application

Overview

This sample application demonstrates basic usage of the WS2812 LED strip driver, for controlling LED strips using WS2812, WS2812b, SK6812, Everlight B1414 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 I2S SDOUT, 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.

Wiring on a thingy52

The thingy52 has integrated NMOS transistors, that can be used instead of a level shifter. The I2S driver supports inverting the output to suit this scheme, using the out-active-low dts property. See the overlay file :zephyr_file:`samples/drivers/led_ws2812/boards/thingy52_nrf52832.overlay` for more detail.

Building and Running

This sample's source directory is :zephyr_file:`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 :kconfig:option:`CONFIG_WS2812_STRIP_SPI` unless you are using an nRF51 SoC, in which case it will be :kconfig:option:`CONFIG_WS2812_STRIP_GPIO`. For the nRF52832, the SPI peripheral might output some garbage at the end of transmissions, and that might confuse older WS2812 strips. Use the I2S driver in those cases.
• create a led-strip :ref:`devicetree alias <dt-alias-chosen>`, which refers to a node in your :ref:`devicetree <dt-guide>` with a worldsemi,ws2812-i2s, worldsemi,ws2812-spi or worldsemi,ws2812-gpio compatible. The node must be properly configured for the driver backend (I2S, SPI or GPIO) and daisy chain length (number of WS2812 chips).

For example devicetree configurations for each compatible, see :zephyr_file:`samples/drivers/led_ws2812/boards/thingy52_nrf52832.overlay`, :zephyr_file:`samples/drivers/led_ws2812/boards/nrf52dk_nrf52832.overlay` and :zephyr_file:`samples/drivers/led_ws2812/boards/nrf51dk_nrf51422.overlay`.

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

Then build and flash the application:

.. zephyr-app-commands::
   :zephyr-app: samples/drivers/led_ws2812
   :board: <board>
   :goals: flash
   :compact:

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

Supported drivers

This sample uses different drivers depending on the selected board:

I2S driver: - thingy52_nrf52832

SPI driver: - mimxrt1050_evk - mimxrt1050_evk_qspi - nrf52dk_nrf52832 - nucleo_f070rb - nucleo_g071rb - nucleo_h743zi - nucleo_l476rg

GPIO driver (cortex-M0 only): - bbc_microbit - nrf51dk_nrf51422

References

• RGB LED strips: an overview
• 74AHCT125 datasheet
• An excellent blog post on WS2812 timing.