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GPIO with custom devicetree binding

Overview

In Zephyr, all hardware-specific configuration is described in the devicetree.

Consequently, also GPIO pins are configured in the devicetree and assigned to a specific purpose using a compatible.

This is in contrast to other embedded environments like Arduino, where e.g. the direction (input / output) of a GPIO pin is configured in the application firmware.

For typical use cases like LEDs or buttons, the existing gpio-leds or gpio-keys compatibles can be used.

This sample demonstrates how to use a GPIO pin for other purposes with a custom devicetree binding.

We assume that a load with high current demands should be switched on or off via a MOSFET. The custom devicetree binding for the power output controlled via a GPIO pin is specified in the file samples/basic/custom_dts_binding/dts/bindings/power-switch.yaml. The gate driver for the MOSFET would be connected to the pin as specified in the .overlay file in the boards folder.

Building and Running

For each board that should be supported, a .overlay file has to be defined in the boards subfolder.

Afterwards, the sample can be built and executed for the <board> as follows:

west build -b <board> samples/basic/custom_dts_binding
west flash

For demonstration purposes, some boards use the GPIO pin of the built-in LED.

Sample output

The GPIO pin should be switched to active level after one second.

The following output is printed:

Initializing pin with inactive level.
Waiting one second.
Setting pin to active level.