rgbyteclock-code/rtc.c

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <struppi@struppi.name> wrote this file. As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return.
 * (c) 2014 Stefan Rupp
 * ----------------------------------------------------------------------------
 */

 
#include <avr/io.h>
#include "rtc.h"
#include <stdlib.h>
#include <avr/interrupt.h>


static volatile uint32_t _rtc_time;

ISR(TIMER2_OVF_vect) {
  ++_rtc_time;
  return;
}

void rtc_init(uint32_t rtc_time)
{
  // Stop all interrupts
  cli();
  TCCR2B = 0;
  TCCR2A = 0;
  TCNT2 = 0;
  // Reset timer to zero
  _rtc_time = rtc_time;

  ASSR = (1<<AS2); // set to asynchronous operation
  TCCR2A = 0;
  TCCR2B = (1<<CS22)|(1<<CS20);
  
  TIMSK2 = (1<<TOIE2); // enable overflow interrupt

  sei();
}


/**
 * Get the current time
 * \return the current time (in s)
 */
inline uint32_t rtc_get(void)
{
  uint32_t t;
  uint8_t sreg;

  sreg = SREG;
  cli();
  t = _rtc_time;
  SREG = sreg;
  return t;
}

#if 0

/**
 * Decode a integer timestamp (in seconds)
 * into days, hours, minutes, seconds
 * \param time the time in seconds
 * \param days will be filled in to contain the days after return
 * \param hours will be filled in to contain the hours after return
 * \param minutes will be filled in to contain the minutes after return
 * \param seconds will be filled in to contain the seconds after return
 * \param ms be filled in to contain the microseconds after return
 */
void rtc_decode(uint32_t time, uint16_t *days, uint8_t *hours, uint8_t *minutes, uint8_t *seconds)
{
  if (seconds != NULL) {
    *seconds = time % 60;
  }
  time /= 60;
  if (minutes != NULL) {
    *minutes = time % 60;
  }
  time /= 60;
  if (hours != NULL) {
    *hours = time;
  }
  return;
}

/**
 * Encode a time given as hours, minutes, seconds and microsecods into a integer storing micorseconds
 * \param time the variable to store the time into
 * \param hour the hours to store
 * \param hour the minutes to store
 * \param hour the seconds to store
 * \param hour the microseconds to store
 */
void timer_encode(uint32_t *time, uint8_t hours, uint8_t minutes, uint8_t seconds, uint16_t ms)
{

  *time = hours;
  *time *= 60;

  *time += minutes;
  *time *= 60;

  *time += seconds;
  *time *= 1000U;

  *time += ms;

  return;
}

/*
void timer_validate(uint8_t *hours, uint8_t *minutes, uint8_t *seconds, uint16_t *ms)
{ 

  while (*ms >= 1000) {
    *ms -= 1000;
    (*seconds)++;
  }

  while (*seconds >= 60) {
    *ms -= 60;
    (*minutes)++;
  }

  while (*minutes >= 60) {
    *minutes -= 60;
    (*hours)++;
  }

  return;
}
*/

#endif