volatile long sekunden;
#define LF_FREQUENCY 32768UL
#define SECONDS(x) ((uint32_t)((LF_FREQUENCY * x) + 0.5))



#ifdef __cplusplus
extern "C" {
#endif

void settimer(){
  NRF_CLOCK->LFCLKSRC = CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos;
  NRF_CLOCK->TASKS_LFCLKSTART = 1;
  while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0);
  NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
  NRF_RTC0->PRESCALER = 0;
  NRF_RTC0->CC[0] = SECONDS(1);
  NRF_RTC0->EVTENSET = RTC_EVTENSET_COMPARE0_Enabled << RTC_EVTENSET_COMPARE0_Pos;
  NRF_RTC0->INTENSET = RTC_INTENSET_COMPARE0_Enabled << RTC_INTENSET_COMPARE0_Pos;
  NVIC_EnableIRQ(RTC0_IRQn);
  NRF_RTC0->TASKS_START = 1;
}
#ifdef __cplusplus
}
#endif


#ifdef __cplusplus
extern "C" {
#endif
void RTC0_IRQHandler(void)
{
  volatile uint32_t dummy;
  if (NRF_RTC0->EVENTS_COMPARE[0] == 1)
  {
    NRF_RTC0->EVENTS_COMPARE[0] = 0;
    NRF_RTC0->CC[0] = NRF_RTC0->COUNTER +  SECONDS(1);
    sekunden++;
    dummy = NRF_RTC0->EVENTS_COMPARE[0];
    dummy;
  }
}
#ifdef __cplusplus
}
#endif