RTC does not advance time counter

[mscovel]

The RTC Time Seconds Register (TSR) and Timer Prescaler Register (TPR) do not increment while the K65 is running/single stepping (nor powered off with a battery connected).

The tower does not have this problem. Both TSR and TPR run (constantly increment) and when powered off/on the TSR is updated to reflect the elapsed time.

Furthermore, the KSDK example rtc_example_twrk65f180m sets an RTC alarm and waits for it to happen. This works on the tower and not on our board. 

I'm thinking there is some K65 errata that Freescale/NXP don't know about yet.

Could this be related to MCG clock speed?

Has anybody seen this problem or does anyone have any idea how to fix it?

[deniscollis]

I had the same problem with a custom K81 board.  The RTC did not run with any new MCUXpresso project.   But it did run with some example code.  On investigation I found that the watchdog setup in the demo checked and set the RTC CR OSCE bit, because it needed the RTC Time Alarm. The side-effect was that the RTC ran beautifully...   until I disabled the watchdog.  To preserve sanity I set the OSCE bit right after the RTC_Init

 rtc_config_t rtcConfig;
 RTC_GetDefaultConfig(&rtcConfig);
 RTC_Init(RTC, &rtcConfig);
 RTC->CR |= RTC_CR_OSCE_MASK; // Enable Oscillator
 RTC_StartTimer(RTC);

[mjbcswitzerland · Accepted solution]

Hi Mark

Check your 32kHz crystal on your own HW - without this oscillating the time will never increment (as in your case).
If this is not the cause, check that the RTC oscillator intialisation has not been missed somehow; ie. setting RTC_CR_OSCE bit in RTC_CR.

Regards

Mark

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[mscovel]

That's what was wrong. The RTC oscillator was not running. Thanks Mark!

[mscovel]

That’s good info Mark. Thank you!

Thanks

Mark Scovel