RTC1 runs too fast

[rgriggs]

Greetings, I am developing an application for the NRF52840 in a RAK Wireless RAK4631, using the Arduino BlueFruit libraries.

When I monitor NRF_RTC1->COUNTER variable, it seems to increment too fast - approximately 2000ms are gained every minute when compared to real time.

The prescaler is set to 31 (NRF_RTC1->PRESCALER) which applies a prescaler of 1024 to the 32768hz RTC.

Can anyone let me know why it would be running so fast?

Thanks,

Ryan

[rgriggs]

Please disregard my question: I just realized that the RTC->COUNTER is NOT milliseconds and must be divided by 1024 instead of 1000 to get accurate seconds.

[Karl Ylvisaker]

Hello Ryan,

I am glad to see that you identified the issue so quickly!
Yes, the COUNTER register will increment each RTC tick, which is not given in milliseconds, and also dependent on the prescaler configuration.

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

Good luck with your development!

Best regards,
Karl