How to recover calendar data after a reset

[Tony.X]

Dear Nordic Developer Zone,

I have implemented a real-time-clock using application timer which is based on the on-chip real-time counter on NRF51822.

A concern of mine is that after a reset due to a unpredictable error( i.e. stack error), is there a way to recover the previous time information?

Thanks, Tony

[Asbjørn]

As @scytulip says, you would have to write the value of the clock/time to flash periodically. This would save it during a reset. RAM will be lost if a reset occurs.

[John]

I would add a caveat to writing the time to flash: We don't know Tony's time accuracy requirement which would dictate how often he needs to save the time. If the time needs to be saved frequently, flash wear would be important. He may need to rotate the saved time through a large set of flash locations to prevent wearing out a single location. He'd also need a way to locate the latest time in flash after a reset. That might be simple if the time was something like a seconds since epoch counter.