for (byte i = 0; i < SLEEP_CYCLES; i++)
{
LowPower.powerDown(SLEEP_4S, ADC_OFF, BOD_OFF);
}
I noticed a additional delay of about 30sec at each loop.
Well, that's new for me. Where do you get time and date from when there is no RTC ?
There's a sleep lib that does that - I can't remember the name but Tom uses it.The sleep library #include <Sleep_n0m1.h> has a calibrate function that adjusts the overall sleep delay by the WDT error. However, even this is an approximation since very long sleep times may drift due to temperature, voltage, solar winds, and other idiosyncrasies of nature.
@Felix: Indeed, that's exactly what I'm doing now i.e. let the gateway keep track of time and date.