root/webserver/example/freeRTOSexample/Source/EnergyMeters/timeConversion.c

#include <targets/LPC23xx.h>
#include "FreeRTOS.h"
#include "MetersIncludes.h"
#include "task.h"
#include "StackMacros.h"

#define MASKSEC 0x3F // Second 00..59 00000000:00000000:00xxxxxx
#define MASKMIN 0x3F00 // Minute 00..59 00000000:00xxxxxx:00000000
#define MASKHR 0x1F0000 // Hour 00..23 000xxxxx:00000000:00000000

extern xTickCount; /* tick counter (milliseconds) from FreeRTOS */

/* taken from Linux Kernel 2.6.30 */
portLONG
mktime(const unsigned int year0, const unsigned int mon0,
       const unsigned int day, const unsigned int hour,
       const unsigned int min, const unsigned int sec);
unsigned long long getEpochTimeWithMs(void)
{
  /* get both registers while in critical section to eliminate the chance of inconsistencies when there are
   * overflows of the SECONDS value.
   */
  unsigned int timeHour;
  unsigned int timeMin;
  unsigned int timeSec;
  unsigned int timeDay;
  unsigned int timeMonth;
  unsigned int timeYear;
  unsigned long long tempTickTime;
  portLONG cTIME0; 
  portLONG cTIME1;

//  portENTER_CRITICAL();
  cTIME0 = RTC_CTIME0;
  cTIME1 = RTC_CTIME1;
//  portEXIT_CRITICAL();


  timeHour = (cTIME0 & MASKHR)>>16;     // Hour
  timeMin = (cTIME0 & MASKMIN)>>8;      // Minute
  timeSec = cTIME0 & MASKSEC;   // Second
  timeDay = cTIME1 & 0xf;           // Day
  timeMonth = (cTIME1 >> 8) & 0xF;  // Month
  timeYear = (cTIME1 >> 16) & 0xFFF; // Year

  /* we get the epoch time, multiply it by 1000 and then add the milliseconds portion
     of the Tick timer. This returns a millisecond time since epoch. 
  */
  tempTickTime = mktime(timeYear, timeMonth, timeDay, timeHour, timeMin, timeSec);
  tempTickTime -= 3600 * 2; /* time zone adaptation (2 h) */
  tempTickTime = (tempTickTime * 1000) + (xTickCount % 1000);
  return tempTickTime;
}


// mktime from linux kernel 2.6.30 kernel / time.c
/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
 *
 * [For the Julian calendar (which was used in Russia before 1917,
 * Britain & colonies before 1752, anywhere else before 1582,
 * and is still in use by some communities) leave out the
 * -year/100+year/400 terms, and add 10.]
 *
 * This algorithm was first published by Gauss (I think).
 *
 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
 * machines where long is 32-bit! (However, as time_t is signed, we
 * will already get problems at other places on 2038-01-19 03:14:08)
 */
portLONG
mktime(const unsigned int year0, const unsigned int mon0,
       const unsigned int day, const unsigned int hour,
       const unsigned int min, const unsigned int sec)
{
        unsigned int mon = mon0, year = year0;

        /* 1..12 -> 11,12,1..10 */
        if (0 >= (int) (mon -= 2)) {
                mon += 12;      /* Puts Feb last since it has leap day */
                year -= 1;
        }

        return ((((portLONG)
                  (year/4 - year/100 + year/400 + 367*mon/12 + day) +
                  year*365 - 719499
            )*24 + hour /* now have hours */
          )*60 + min /* now have minutes */
        )*60 + sec; /* finally seconds */
}