efc0e75463
Using a gpio_dt_spec is the current best practice for getting at pins defined in the DT, because it gets all the boilerplate and flags right for you. Use that in blinky, keeping the documentation in sync with the code. Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
96 lines
2.5 KiB
ReStructuredText
96 lines
2.5 KiB
ReStructuredText
.. _blinky-sample:
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Blinky
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######
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Overview
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********
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The Blinky sample blinks an LED forever using the :ref:`GPIO API <gpio_api>`.
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The source code shows how to:
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#. Get a pin specification from the :ref:`devicetree <dt-guide>` as a
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:c:struct:`gpio_dt_spec`
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#. Configure the GPIO pin as an output
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#. Toggle the pin forever
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See :ref:`pwm-blinky-sample` for a similar sample that uses the PWM API instead.
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.. _blinky-sample-requirements:
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Requirements
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************
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Your board must:
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#. Have an LED connected via a GPIO pin (these are called "User LEDs" on many of
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Zephyr's :ref:`boards`).
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#. Have the LED configured using the ``led0`` devicetree alias.
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Building and Running
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********************
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Build and flash Blinky as follows, changing ``reel_board`` for your board:
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.. zephyr-app-commands::
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:zephyr-app: samples/basic/blinky
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:board: reel_board
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:goals: build flash
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:compact:
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After flashing, the LED starts to blink. If a runtime error occurs, the sample
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exits without printing to the console.
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Build errors
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************
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You will see a build error at the source code line defining the ``struct
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gpio_dt_spec led`` variable if you try to build Blinky for an unsupported
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board.
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On GCC-based toolchains, the error looks like this:
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.. code-block:: none
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error: '__device_dts_ord_DT_N_ALIAS_led_P_gpios_IDX_0_PH_ORD' undeclared here (not in a function)
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Adding board support
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********************
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To add support for your board, add something like this to your devicetree:
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.. code-block:: DTS
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/ {
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aliases {
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led0 = &myled0;
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};
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leds {
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compatible = "gpio-leds";
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myled0: led_0 {
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gpios = <&gpio0 13 GPIO_ACTIVE_LOW>;
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};
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};
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};
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The above sets your board's ``led0`` alias to use pin 13 on GPIO controller
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``gpio0``. The pin flags :c:macro:`GPIO_ACTIVE_HIGH` mean the LED is on when
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the pin is set to its high state, and off when the pin is in its low state.
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Tips:
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- See :dtcompatible:`gpio-leds` for more information on defining GPIO-based LEDs
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in devicetree.
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- If you're not sure what to do, check the devicetrees for supported boards which
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use the same SoC as your target. See :ref:`get-devicetree-outputs` for details.
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- See :zephyr_file:`include/dt-bindings/gpio/gpio.h` for the flags you can use
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in devicetree.
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- If the LED is built in to your board hardware, the alias should be defined in
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your :ref:`BOARD.dts file <devicetree-in-out-files>`. Otherwise, you can
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define one in a :ref:`devicetree overlay <set-devicetree-overlays>`.
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