RTC weird on nrf52832

RE: RTC weird on nrf52832

pellepl — Wed, 22 Dec 2021 07:41:39 GMT

I cannot reproduce this anymore, so I'll conclude it was a fluke of some sort. If we stumble on it again I'll try to gather more data.

Thanks for the help and merry Christmas!

RE: RTC weird on nrf52832

pellepl — Thu, 16 Dec 2021 08:25:09 GMT

Hi Sigurd,

sorry for belated reply. The marking on the chip says QFAAE1 2114FA, In production we're using the nrfx drivers, this example is boiled down for clarity.

Turns out a power cycle resolves it. The processors are in a bit awkward position to easily cold boot.

My gut feeling is that we've gotten into this state by numerous debugging sessions and flashings on perhaps bad timings. But it is a little scary that we got in this state as we're relying on the rtc to work. I'll see if I can reproduce it.

RE: RTC weird on nrf52832

hmolesworth — Wed, 15 Dec 2021 20:50:38 GMT

This is not necessarily the issue, but I suggest changing the position of DSB to ensure the start completes before attempting to read. Additionally continuous reading of the counter register by the 64MHz cpu thrashes the bus pathwys between CPU and the 32kHz RTC and may (will) cause issues,

Change:
    NRF_RTC2->TASKS_START = 1;
    //while (NRF_RTC2->COUNTER == 0); // HANG 4ever :(
    __DSB();
To:
    NRF_RTC2->TASKS_START = 1;
    __DSB();
    while (NRF_RTC2->COUNTER == 0) nrf_delay_usec(200); // HANG 4ever :(

RE: RTC weird on nrf52832

Sigurd — Tue, 14 Dec 2021 14:31:11 GMT

Hi,

I'm not seeing this when testing on nRF52832-DKs. Can you try to call nrfx_clock_anomaly_132() before triggering LFCLKSTART ?

PS: I recommend using the nrfx driver.

RE: RTC weird on nrf52832

pellepl — Fri, 10 Dec 2021 16:01:13 GMT

Hi, thanks for answering.

I'm pretty sure it is newer than that as it came from the factory this autumn, but will check for sure coming Monday.

Also, it affects all three RTCs in fact, the RTC2 is simply the last one I tested.

Finally, turns out a full power cycle recovers it. A reset via nrfjprog -r does not. Have yet to test nvic reset. We have no pin reset. And no idea of how we got to this state.

Cheers,

Peter

RE: RTC weird on nrf52832

Sigurd — Fri, 10 Dec 2021 15:51:44 GMT

Hi,

What is the IC marking on the nRF52832 that fails?

Are you using some old nRF52832 Engineering A devices here ? If yes, then this errata would explain the issue: https://infocenter.nordicsemi.com/topic/errata_nRF52832_EngA/ERR/nRF52832/EngineeringA/latest/anomaly_832_10.html