Simple IRQ Button Debounce for Raspberry Pi Pico

main.c

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


static const uint8_t DEBOUNCE = 50;
static bool pressed = false;
static int32_t alarm_id = 0;

int64_t enable_button(alarm_id_t alarm_id, void *user_data) {
    pressed = false;
    return 0;
}

void gpio_callback(uint gpio, uint32_t events) {
    if (pressed) {
        cancel_alarm(alarm_id);
    } else {
        pressed = true;
        printf("Button pressed: %d\n", gpio);
    }

    alarm_id = add_alarm_in_ms(DEBOUNCE, enable_button, NULL, false);
}


int main() {
    const uint LED_PIN = PICO_DEFAULT_LED_PIN;
    const uint32_t events = GPIO_IRQ_LEVEL_HIGH;
    const uint8_t sleep_time = 250;
    stdio_init_all();

    gpio_init(LED_PIN);
    gpio_set_dir(LED_PIN, GPIO_OUT);

    gpio_init(21);
    gpio_pull_down(21);
    gpio_init(15);
    gpio_pull_down(15);
    gpio_init(16);
    gpio_pull_down(16);

    gpio_set_irq_enabled_with_callback(21, events, true, &gpio_callback);
    gpio_set_irq_enabled(16, events, true);
    gpio_set_irq_enabled(15, events, true);

    while(1) {
        gpio_put(LED_PIN, 1);
        sleep_ms(sleep_time);
        gpio_put(LED_PIN, 0);
        sleep_ms(sleep_time);
    }
}

// vim: sw=4 ts=4 et