Reading and writing 📝📂 to nRF9160 Flash Memory

.. _blinky-sample:

Blinky

Overview

The Blinky sample blinks an LED forever using the :ref:GPIO API <gpio_api>.

The source code shows how to:

#. Get a pin specification from the :ref:devicetree <dt-guide> as a :c:struct:gpio_dt_spec #. Configure the GPIO pin as an output #. Toggle the pin forever

See :ref:pwm-blinky-sample for a similar sample that uses the PWM API instead.

.. _blinky-sample-requirements:

Requirements

Your board must:

#. Have an LED connected via a GPIO pin (these are called "User LEDs" on many of Zephyr's :ref:boards). #. Have the LED configured using the led0 devicetree alias.

Building and Running

Build and flash Blinky as follows, changing reel_board for your board:

.. zephyr-app-commands:: :zephyr-app: samples/basic/blinky :board: reel_board :goals: build flash :compact:

After flashing, the LED starts to blink. If a runtime error occurs, the sample exits without printing to the console.

Build errors

You will see a build error at the source code line defining the struct gpio_dt_spec led variable if you try to build Blinky for an unsupported board.

On GCC-based toolchains, the error looks like this:

.. code-block:: none

error: '__device_dts_ord_DT_N_ALIAS_led_P_gpios_IDX_0_PH_ORD' undeclared here (not in a function)

Adding board support

To add support for your board, add something like this to your devicetree:

.. code-block:: DTS

/ { aliases { led0 = &myled0; };

leds {
	compatible = "gpio-leds";
	myled0: led_0 {
		gpios = <&gpio0 13 GPIO_ACTIVE_LOW>;
            };
};

};

The above sets your board's led0 alias to use pin 13 on GPIO controller gpio0. The pin flags :c:macro:GPIO_ACTIVE_HIGH mean the LED is on when the pin is set to its high state, and off when the pin is in its low state.

Tips:

• See :dtcompatible:gpio-leds for more information on defining GPIO-based LEDs in devicetree.

• If you're not sure what to do, check the devicetrees for supported boards which use the same SoC as your target. See :ref:get-devicetree-outputs for details.

• See :zephyr_file:include/zephyr/dt-bindings/gpio/gpio.h for the flags you can use in devicetree.

• If the LED is built in to your board hardware, the alias should be defined in your :ref:BOARD.dts file <devicetree-in-out-files>. Otherwise, you can define one in a :ref:devicetree overlay <set-devicetree-overlays>.