Blinky is a simple application which blinks an LED forever using the :ref:`GPIO API <gpio_api>`. The source code shows how to configure GPIO pins as outputs, then turn them on and off.
See :ref:`pwm-blinky-sample` for a sample which uses the PWM API to blink an LED.
You will see this error if you try to build Blinky for an unsupported board:
Unsupported board: led0 devicetree alias is not defined
The board must have an LED connected via a GPIO pin. These are called "User
LEDs" on many of Zephyr's :ref:`boards`. The LED must be configured using the
led0 :ref:`devicetree <dt-guide>` alias. This is usually done in the
:ref:`BOARD.dts file <devicetree-in-out-files>` or a :ref:`devicetree overlay
<set-devicetree-overlays>`.
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. Blinky does not print to the console.