4.3. Code Examples

4.3.1. Turn Onboard LED On

The Raspberry Pi Pico board has a green LED already connected to GPIO 25. Following code configures GPIO 25 as an output and turns the LED on.

#include <pico/stdlib.h>
#include <hardware/gpio.h>

#define LED_PIN 25                  // Define a pin number macro to use it throughout the code

int main()
{
    gpio_init(LED_PIN);             // Initialize GPIO 25 to the default state
    gpio_set_dir(LED_PIN, true);    // Configure GPIO 25 as an output
    gpio_put(LED_PIN, true);        // Drive GPIO 25 to High

    while (true);
}

4.3.2. Read HIGH or LOW using a GPIO

Following code configures a GPIO as an input. The exact configuration can be set by changing values in gpio_set_pulls function.

#include <stdio.h>
#include <pico/stdlib.h>
#include <hardware/gpio.h>

void setup()
{
    stdio_init_all();

    gpio_init(0);
    gpio_set_dir(0,0);
    gpio_set_pulls(0,0,0); // Change GPIO input configuration to see different behavior
}

void loop()
{
    bool x = gpio_get(0); // Read GPIO state, i.e. HIGH or LOW
    printf("%u\r\n",x); // Print out the GPIO state as 1 or 0
}

int main()
{
    setup();
    while (true)
        loop();
}