debounce_button.c

#include "debounce_button.h"

static debounce_button_data* debounce_list = NULL; // Holds head of list
static void debounceButtonCallback(uint gpio, uint32_t events);
static int64_t debounceButtonTimerCallback(alarm_id_t id, void *user_data);

void debounceButtonCreate(debounce_button_data* db, uint pin, uint delay_ms, event_callback_t event_callback, bool up, bool high)
{
    // Add to end of list
    if (!debounce_list)
    {
        debounce_list = db;
    }
    else
    {
        debounce_button_data* db_prev = debounce_list;

        while (db_prev->next)
        {
            db_prev = db_prev->next;
        }
        db_prev->next = db;
    }
    db->next = NULL;

    db->pin = pin;
    db->delay_ms = delay_ms;
    db->event_callback = event_callback;
    db->up = up;
    db->high = high;
    db->timer_id = -1;

    gpio_init(db->pin);
    gpio_set_dir(db->pin, GPIO_IN);

    (db->up) ? gpio_pull_up(db->pin) : gpio_pull_down(db->pin);

    // Attach the interrupt handler
    gpio_set_irq_enabled_with_callback(db->pin, db->high ? GPIO_IRQ_EDGE_RISE : GPIO_IRQ_EDGE_FALL, true, &debounceButtonCallback);
}

void debounceButtonDestroy(debounce_button_data* db)
{
    // Disable the IRQ
    gpio_set_irq_enabled_with_callback(db->pin, db->high ? GPIO_IRQ_EDGE_RISE : GPIO_IRQ_EDGE_FALL, false, &debounceButtonCallback);

    // Kill any timer
    if (db->timer_id != -1)
    {
        // Cancel a timer if it was running
        cancel_alarm(db->timer_id);
        db->timer_id = -1;
    }

    // Remove from linked list - strictly speaking this should be interrupt protected

    // Is this the head?
    if (debounce_list == db)
    {
        debounce_list = db->next;
    } 
    else
    {
        // Walk the list to find our position
        debounce_button_data* p = debounce_list;
        while (p->next != db)
        {
            p = p->next;
        }
    
        // p is now the entry before us, so link to next
        p->next = db->next; 
    }
}

static void debounceButtonCallback(uint gpio, uint32_t events)
{
    // Find this block in the linked list
    debounce_button_data* db = debounce_list;

    while ((db != NULL) && db->pin != gpio)
    {
        db = db->next;
    }

    if (db)
    {
            if (db->timer_id == -1)
            {
                // Timer not running so create one
                db->timer_id = add_alarm_in_ms(db->delay_ms, debounceButtonTimerCallback, db, true);
            }
    }
    gpio_acknowledge_irq(gpio, events);
}

// Called when the timer fires
// Send data back to the application
static int64_t debounceButtonTimerCallback(alarm_id_t id, void* db) 
{
    // Is the button pressed?
    if ((((debounce_button_data*)db)->timer_id != -1) && 
          (gpio_get(((debounce_button_data*)db)->pin) == ((debounce_button_data*)db)->high))
    {
        ((debounce_button_data*)db)->event_callback(((debounce_button_data*)db)->pin, single_press);
    }

    // Clear timer indicator
    ((debounce_button_data*)db)->timer_id = -1;
    return 0;
}