zephyr-gpio

Zephyr GPIO Skill

Overview

This skill provides guidance for implementing GPIO functionality in Zephyr RTOS applications. GPIO (General Purpose Input/Output) is fundamental to embedded systems for controlling LEDs, reading buttons, and interfacing with digital peripherals.

API Selection Decision Tree

Need GPIO?
├── Single pin from devicetree?
│   └── Use gpio_dt_spec + _dt() functions (RECOMMENDED)
│       └── GPIO_DT_SPEC_GET(node, prop) → gpio_pin_configure_dt() → gpio_pin_set_dt()/gpio_pin_get_dt()
│
├── Multiple pins, same port?
│   └── Use gpio_port_*() functions for efficiency
│       └── gpio_port_set_masked() / gpio_port_get()
│
└── Runtime-determined pin?
    └── Use raw API with device + pin number
        └── DEVICE_DT_GET() → gpio_pin_configure() → gpio_pin_set()/gpio_pin_get()

Getting Device Reference

From Devicetree (Preferred)

/* For nodes with gpios property (e.g., gpio-leds, gpio-keys) */
#define LED_NODE DT_ALIAS(led0)
static const struct gpio_dt_spec led = GPIO_DT_SPEC_GET(LED_NODE, gpios);

/* Check device readiness before use */
if (!gpio_is_ready_dt(&led)) {
    return -ENODEV;
}

gpio_dt_spec Structure

struct gpio_dt_spec {
    const struct device *port;  /* GPIO controller device */
    gpio_pin_t pin;             /* Pin number (0-31 typically) */
    gpio_dt_flags_t dt_flags;   /* Flags from devicetree (e.g., GPIO_ACTIVE_LOW) */
};

Common Workflows

1. Basic LED Blinky

#include <zephyr/kernel.h>
#include <zephyr/drivers/gpio.h>

#define LED_NODE DT_ALIAS(led0)
static const struct gpio_dt_spec led = GPIO_DT_SPEC_GET(LED_NODE, gpios);

int main(void)
{
    if (!gpio_is_ready_dt(&led)) {
        return -ENODEV;
    }

    int ret = gpio_pin_configure_dt(&led, GPIO_OUTPUT_ACTIVE);
    if (ret < 0) {
        return ret;
    }

    while (1) {
        gpio_pin_toggle_dt(&led);
        k_msleep(1000);
    }
    return 0;
}

2. Button Input (Polled)

#define BUTTON_NODE DT_ALIAS(sw0)
static const struct gpio_dt_spec button = GPIO_DT_SPEC_GET(BUTTON_NODE, gpios);

int main(void)
{
    if (!gpio_is_ready_dt(&button)) {
        return -ENODEV;
    }

    gpio_pin_configure_dt(&button, GPIO_INPUT);

    while (1) {
        int val = gpio_pin_get_dt(&button);
        if (val > 0) {
            /* Button pressed (handles ACTIVE_LOW automatically) */
        }
        k_msleep(100);
    }
}