drivers/misc/debounce.c

   1 /* Author: Domen Puncer Kugler <domen@cba.si>.  License: WTFPL, see file LICENSE */
   2
   3 /* see A guide to debouncing: http://www.eng.utah.edu/~cs5780/debouncing.pdf */
   4
   5
   6 /* Feature requests:
   7  * - how long is the switch held
   8  */
   9
  10 #include <stdio.h>
  11
  12 #include <drivers/debounce.h>
  13 #include <gpio.h>
  14
  15
  16 /* debounce_periodic should be called every 5ms or so.
  17  * With 8 pulses this makes it 40ms delay, which should not be noticeable */
  18
  19 /* It is assumed debounce_register is never called after debounce_periodic */
  20
  21 #define DEBOUNCE_PULSES 8
  22
  23 static LIST_DECLARE_INIT(debounce_list);
  24 //static LOCK_DECLARE_INIT(debounce_list_lock);
  25
  26 int debounce_register(struct debounce_info *deb)
  27 {
  28 //      lock(&debounce_list_lock);
  29         list_add_tail(&debounce_list, &deb->list);
  30         deb->history = 0xffffff * gpio_get(deb->pin);
  31 //      unlock(&debounce_list_lock);
  32
  33         return 0;
  34 }
  35
  36 #define DEBOUNCE_BITS_MASK ((1<<(DEBOUNCE_PULSES+1))-1) /* 0x1ff */
  37 #define DEBOUNCE_BITS_FALLING (1<<DEBOUNCE_PULSES)      /* 0x100 */
  38 #define DEBOUNCE_BITS_RISING  ((1<<DEBOUNCE_PULSES)-1)  /* 0x0ff */
  39 int debounce_periodic()
  40 {
  41 //      lock(&debounce_list_lock);
  42         struct list *it;
  43         list_for_each(&debounce_list, it) {
  44                 struct debounce_info *deb = list_entry(it, struct debounce_info, list);
  45                 u32 h = (deb->history<<1) | gpio_get(deb->pin);
  46                 h &= DEBOUNCE_BITS_MASK;
  47                 deb->history = h;
  48
  49                 if ((deb->settings & DEBOUNCE_FALLING) && h == DEBOUNCE_BITS_FALLING)
  50                         deb->callback(deb->pin, 0);
  51                 if ((deb->settings & DEBOUNCE_RISING) && h == DEBOUNCE_BITS_RISING)
  52                         deb->callback(deb->pin, 1);
  53         }
  54 //      unlock(&debounce_list_lock);
  55         return 0;
  56 }