92145a22d3
The chain-length DTS property is now mandatory, so remove the optional Kconfig for setting the length Signed-off-by: Jamie McCrae <spam@helper3000.net>
100 lines
3.4 KiB
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100 lines
3.4 KiB
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.. zephyr:code-sample:: led-strip
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:name: LED strip
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:relevant-api: led_strip_interface
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Control an LED strip example.
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Overview
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********
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This sample application demonstrates basic usage of the LED strip.
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Requirements
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************
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Zephyr supports various LED strip chips. For example,
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- WS2812, such as the `NeoPixel(WS2812 compatible) LED Strip from AdaFruit`_.
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- APA102, such as the `Dotstar(APA102 compatible) LED Strip from AdaFruit`_.
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- LPD8806, such as the `LPD8806 LED Strip from AdaFruit`_.
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- Power supply. These LED strips usually require a 5V supply.
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- If the LED strip connects to the SPI bus, SPI communications usually use 5V
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signaling, which may require a level translator, such as the
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`74AHCT125 datasheet`_.
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.. _NeoPixel(WS2812 compatible) LED Strip from AdaFruit: https://www.adafruit.com/product/3919
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.. _Dotstar(APA102 compatible) LED Strip from AdaFruit: https://www.adafruit.com/product/2242
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.. _LPD8806 LED Strip from AdaFruit: https://www.adafruit.com/product/1948
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.. _74AHCT125 datasheet: https://cdn-shop.adafruit.com/datasheets/74AHC125.pdf
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Wiring
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******
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APA020 and LPD880x
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==================
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#. Ensure your Zephyr board, the 5V power supply, and the LED strip
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share a common ground.
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#. Connect the MOSI pin of your board's SPI master to the data input
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pin of the first IC in the strip.
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#. Connect the SCLK pin of your board's SPI master to the clock input
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pin of the first IC in the strip.
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#. Connect the 5V power supply pin to the 5V input of the LED strip.
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WS2812
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======
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#. Ensure your Zephyr board, and the LED strip share a common ground.
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#. Connect the LED strip control pin (either I2S SDOUT, SPI MOSI or GPIO) from
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your board to the data input pin of the first WS2812 IC in the strip.
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#. Power the LED strip at an I/O level compatible with the control pin signals.
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Note about thingy52
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-------------------
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The thingy52 has integrated NMOS transistors, that can be used instead of a level shifter.
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The I2S driver supports inverting the output to suit this scheme, using the ``out-active-low`` dts
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property. See the overlay file
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:zephyr_file:`samples/drivers/led_strip/boards/thingy52_nrf52832.overlay` for more detail.
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Building and Running
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********************
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The sample updates the LED strip periodically. The update frequency can be
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modified by changing the :kconfig:option:`CONFIG_SAMPLE_LED_UPDATE_DELAY`.
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Then build and flash the application:
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.. zephyr-app-commands::
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:zephyr-app: samples/drivers/led_strip
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:board: <board>
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:goals: flash
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:compact:
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When you connect to your board's serial console, you should see the
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following output:
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.. code-block:: none
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***** Booting Zephyr OS build v2.1.0-rc1-191-gd2466cdaf045 *****
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[00:00:00.005,920] <inf> main: Found LED strip device WS2812
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[00:00:00.005,950] <inf> main: Displaying pattern on strip
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References
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**********
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- `WS2812 datasheet`_
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- `LPD8806 datasheet`_
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- `APA102C datasheet`_
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- `74AHCT125 datasheet`_
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- `RGB LED strips: an overview`_
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- An excellent `blog post on WS2812 timing`_.
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.. _WS2812 datasheet: https://cdn-shop.adafruit.com/datasheets/WS2812.pdf
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.. _LPD8806 datasheet: https://cdn-shop.adafruit.com/datasheets/lpd8806+english.pdf
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.. _APA102C datasheet: https://cdn-shop.adafruit.com/product-files/2477/APA102C-iPixelLED.pdf
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.. _blog post on WS2812 timing: https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
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.. _RGB LED strips\: an overview: http://nut-bolt.nl/2012/rgb-led-strips/
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