timer.c

/* sd2snes - SD card based universal cartridge for the SNES
   Copyright (C) 2009-2010 Maximilian Rehkopf <otakon@gmx.net>
   This file was adapted from sd2iec, written by Ingo Korb.
   Original copyright header follows:
*/
/* sd2iec - SD/MMC to Commodore serial bus interface/controller
   Copyright (C) 2007-2009  Ingo Korb <ingo@akana.de>

   Inspiration and low-level SD/MMC access based on code from MMC2IEC
     by Lars Pontoppidan et al., see sdcard.c|h and config.h.

   FAT filesystem access based on code from ChaN and Jim Brain, see ff.c|h.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License only.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


   timer.c: System timer (and button debouncer)

*/

#include "config.h"
#include <avr/interrupt.h>
#include <avr/io.h>
#include "avrcompat.h"
#include "led.h"
#include "timer.h"

volatile tick_t ticks;
// Logical buttons
volatile uint8_t active_keys;

// Physical buttons
uint8_t buttonstate;
tick_t  lastbuttonchange;

/* Called by the timer interrupt when the button state has changed */
static void buttons_changed(void) {
  /* Check if the previous state was stable for two ticks */
  if (time_after(ticks, lastbuttonchange+2)) {
    if (active_keys & IGNORE_KEYS) {
      active_keys &= ~IGNORE_KEYS;
    } else if (!(buttonstate & (BUTTON_PREV|BUTTON_NEXT))) {
      /* Both buttons held down */
        active_keys |= KEY_HOME;
    } else if (!(buttonstate & BUTTON_NEXT) &&
               (BUTTON_PIN & BUTTON_NEXT)) {
      /* "Next" button released */
      active_keys |= KEY_NEXT;
    } else if (!(buttonstate & BUTTON_PREV) &&
               (BUTTON_PIN & BUTTON_NEXT)) {
      active_keys |= KEY_PREV;
    }
  }

  lastbuttonchange = ticks;
  buttonstate = BUTTON_PIN & BUTTON_MASK;
}

/* The main timer interrupt */
ISR(TIMER1_COMPA_vect) {
  uint8_t tmp = BUTTON_PIN & BUTTON_MASK;

  if (tmp != buttonstate) {
    buttons_changed();
  }

  ticks++;

#ifdef SINGLE_LED
  if (led_state & LED_ERROR) {
    if ((ticks & 15) == 0)
      DIRTY_LED_PORT ^= DIRTY_LED_BIT();
  } else {
    if ((led_state & LED_BUSY) || (led_state & LED_DIRTY)) {
      DIRTY_LED_ON();
    } else {
      DIRTY_LED_OFF();
    }
  }
#else
  if (led_state & LED_ERROR)
    if ((ticks & 15) == 0)
      DIRTY_LED_PORT ^= DIRTY_LED_BIT();
#endif

  /* Sleep button triggers when held down for 2sec */
  if (time_after(ticks, lastbuttonchange+2)) {
    if (!(buttonstate & BUTTON_NEXT) &&
        (buttonstate & BUTTON_PREV) &&
        time_after(ticks, lastbuttonchange+2*HZ) &&
        !key_pressed(KEY_SLEEP)) {
      /* Set ignore flag so the release doesn't trigger KEY_NEXT */
      active_keys |= KEY_SLEEP | IGNORE_KEYS;
      /* Avoid triggering for the next two seconds */
      lastbuttonchange = ticks;
    }
  }
#if CONFIG_RTC_VARIANT == 1
  increment_rtc();
#endif

#ifdef CONFIG_REMOTE_DISPLAY
  /* Check if the display wants to be queried */
  if (!(SOFTI2C_PIN & _BV(SOFTI2C_BIT_INTRQ))) {
    active_keys |= KEY_DISPLAY;
  }
#endif
}

void timer_init(void) {
  /* Count F_CPU/8 in timer 0 */
  TCCR0B = _BV(CS01);

  /* Set up a 100Hz interrupt using timer 1 */
  OCR1A  = 1249;
  TCNT1  = 0;
  TCCR1A = 0;
  TCCR1B = _BV(WGM12) | _BV(CS10) | _BV(CS11);
  TIMSK1 |= _BV(OCIE1A);

  /* Buttons */
  BUTTON_DDR  &= (uint8_t)~BUTTON_MASK;
  BUTTON_PORT |= BUTTON_MASK;
}