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zephyr/samples/drivers/led_ws2812
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Martí Bolívar 1d2a551c65 drivers: led_strip: modernize and fix up ws2812 drivers/sample 
Convert the GPIO based driver to the new GPIO API. (Only the
gpio_configure() call is affected).

Move configuration to DT where appropriate for both SPI and GPIO
drivers, only leaving the SPI vs. GPIO decision in Kconfig (in
addition to the basic enable for the driver.) Move some files around
to clean up as a result of this change.

led_ws2812 sample changes:

- make the pattern easier to look at by emitting less light

- use led_strip alias from DT to get strip device, allocate
  appropriate struct led_rgb buffer, etc.

- move the pins around and remove 96b_carbon support (I have no board
  to test with)

GPIO driver specific changes:

- str is required to write OUTSET/OUTCLR, not strb. The registers
  are word-sized.

- the str[b] registers must all be in r0-r7, so "l" is the correct GCC
  inline assembly constraint for both "base" and "pin"

SPI driver specific changes:

- match the GPIO driver in not supporting the update_channels API
  method, which never made sense for this type of strip

- return -ENOMEM when the user tries to send more pixel data
  than we have buffer space for instead of -EINVAL

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
 		2020-02-05 12:00:36 +01:00
..
boards
…
src
…
CMakeLists.txt
…
Kconfig
…
README.rst
…
nrf52-bindings.h
…
prj.conf
…
sample.yaml
…

README.rst 

.. _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 <device-tree>` 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/nrf52_pca10040.overlay` and
:zephyr_file:`samples/drivers/led_ws2812/boards/nrf51_pca10028.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`_.