Workflow

1.
Create alarm struct and initialize the time with current time.
```
struct rtc_calendar_alarm_time alarm;
```

Set alarm to trigger on seconds only.

alarm.mask = RTC_CALENDAR_ALARM_MASK_SEC;

Add one second to the current time and set new alarm.

alarm.time.second += 5;
alarm.time.second = alarm.time.second % 60;

rtc_calendar_set_alarm(&rtc_instance, &alarm, RTC_CALENDAR_ALARM_0);