.. _led_ws2812_sample:
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
************
.. _NeoPixel Ring 12 from AdaFruit: https://www.adafruit.com/product/1643
.. _74AHCT125: https://cdn-shop.adafruit.com/datasheets/74AHC125.pdf
- 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
******
#. Ensure your Zephyr board, and the LED strip share a common ground.
#. 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.
#. Power the LED strip at an I/O level compatible with the control pin signals.
Building and Running
********************
.. _blog post on WS2812 timing: https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
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 :option:`CONFIG_WS2812_STRIP_SPI` unless you are using an nRF51 SoC, in
which case it will be :option:`CONFIG_WS2812_STRIP_GPIO`.
- 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-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
: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:
.. code-block:: none
***** 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
References
**********
- `RGB LED strips: an overview <http://nut-bolt.nl/2012/rgb-led-strips/>`_
- `74AHCT125 datasheet
<https://cdn-shop.adafruit.com/datasheets/74AHC125.pdf>`_
- An excellent `blog post on WS2812 timing`_.
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