Colony

  time.c

  anything that requires a delay

  mostly delay_ms

  author: Robotics Club, Colony Project

  Change Log:

  2.5.07 - Kevin

  Aaron fixed the orb/servo code and made them use timer3 but compare registers B and C. He hard set the prescaler

  to 8 so the RTC broke. Changed it so that we use a 8 prescaler which sets the compare match at 1/16th of a second.

  You now count how many 16ths of a second you want until you trigger your actual interrupt. Works. Changed defines

  for time so you can still call rtc_init with a scale but now it is defined in terms of actual time like second, quarter_second

  etc. Read that section in the time.h file for more information. Tested and works, though the clock drifts more than

  it used to

  1.30.07 - Kevin

  Modified the clock to run on timer3 on the Dragonfly. Works with decent accuracy. Using a prescaler of 256

  the timer counts up to a precomputer value which will trigger an interrupt and reset the timer. Multiples of

  256 change it by that multiple. Refer to the time.h file for all possible prescalers.

  The interrupt will call a specified function _rtc_func every pulse.

  All of it has been tested and it works.

void delay_ms(int ms) {

  for(; ms > 15; ms-=15)

    _delay_ms(15);

  _delay_ms(ms);

  //Clear timer register for Timer 3

  TCNT3 = 0;

  /* 	This sets the Waveform Generation Module to CTC (Clear Timer on Compare) Mode (100)

	See page135 in Atmega128 Docs for more modes and explanations */

  TCCR3B |= _BV(WGM32);

  /* 	This sets the prescaler for the system clock (8MHz) ie: divides the clock by some number.

	Currently set to a prescaler of 8 because that is what the orb and servos use (they are on this timer as well)

	See page137 in Atemga128 Docs for all the available prescalers */

  TCCR3B |= _BV(CS31);

  /* 	Sets the two regsiters that we compare against. So the timer counts up to this number and

	then resets back to 0 and calls the compare match interrupt.

	8x10^6 / 8 = 1/16 Second. All values are based off of this number. Do not change it unless you

	are l337*/

  OCR3A = 0xF424;	

  /* 	Enable Output Compare A Interrupt. When OCR3A is met by the timer TCNT3 this interrupt will be

	triggerd. (See page140 in Atmega128 Docs for more information */

  ETIMSK |= _BV(OCIE3A);

  /*	Store the pointer to the function to be used in the interrupt */

  _rtc_f = rtc_func;

  /*	Store how many 1/16ths of a second you want to let by before triggering an interrupt */

  _rtc_scale = prescale_opt;

int rtc_get(void) {

  return _rtc_val;

void rtc_reset(void) {

  _rtc_val = 0;

  if (_rtc_pulse ==  _rtc_scale) {

    //Increment the real time clock counter

    _rtc_val++;

    //Calls the function tied to the real time clock if defined

    if(_rtc_f != 0)

      _rtc_f();

    //Resets the pulse until the next scale is matched

    _rtc_pulse = 0;

  }	

  //Updates the amount of pulses seen since the last scale match

  _rtc_pulse++;