Why does the AVR clock display a flashing letter P?
This happens when the AVR clock is in back-up mode, i.e., it does not receive the 1 PPS signal (1 Pulse per Second) from the RTC (or another external source). The AVR clock has a countdown timer that is activated after roughly 1 1/30 second (based on its own crystal oscillator), and it advances the time if no PPS signal was received. This will most likely happen when a GPS device feeds the 1PPS signal and the device looses its satellite lock. The clock will keep going in that case, though running a little slow. If you have the NMEA output of the GPS device connected to the Serial Port (and the GPS option is selected with the proper local time zone offset), the AVR clock will automatically set the proper time and date once the GPS device gets another lock. A flashing letter “G” indicates the the time or date was changed based on the incoming NMEA records. The RTC has its own backup battery and is always powered. To reset the RTC, please remove it from its socket and reinsert it (with th
