Retaining RTC Time After resetting NRF52840.

Question

Hello Respected members, I have a question regarding the #nrf5-calendar example that is, is there any way to retain the NRF52 time after resetting the device. I am using the nrf_calendar example which is using RTC0 and when I reset the device the time is no longer retained ( which I have set from the GUI). Now my question is, is there any way to retain the time even after resetting the device, should I go for app_timer instead of RTC, or do I have to store the time in flash which holds the values after reset. If flash is the solution then kindly elaborate how would I save time values in flash.
Thanks and regards
Engr. Sami Ul Haq

Karl Ylvisaker · Accepted Answer

Hello Sami Ul Haq, While it could be possible to store the date to flash, I am not sure that this would be feasible for a calendar application since the device does not know how long it has been in SYSTEM_OFF mode - so if the last thing written to flash was 60 days ago, it will not have any way to know this, and it will resume its RTC as if no time has passed. The only thing this would tell is with certainty is that the date and time in flash has passed, at least. There is unfortunately no way to resume the RTC and date-time keeping in a more accurate way through a SYSTEM_OFF, since the RTC also is off during this time. My advice would be to connect to the device following a reset, and update / synchronize the calendar time before starting operation again. If your application really needs to keep track of the time passed in SYSTEM_OFF sleep you might have to add an external RTC that could do this for you while the nRF is in SYSTEM_OFF sleep. Best regards, Karl

Karl Ylvisaker · Answer

No problem at all, Sami Ul Haq - I am happy to help you!

Please do not hesitate to open another ticket if you should encounter any other issues or questions in the future.

Good luck with your development!

Best regards,
Karl

Retaining RTC Time After resetting NRF52840.

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