Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

RE: Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

Luis — Tue, 30 Apr 2024 18:24:13 GMT

I just tested your code and it does indeed works. I don't know what I was doing wrong before.

So I am able to disable the external clock now with that code.

RE: Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

Kenneth — Tue, 30 Apr 2024 17:21:18 GMT

Unfortunately I don't have an external clock to test with, at least not right away.

Can you just confirm that the following code then will fail?

[quote user="Luis Filipe Rossi"]I tryed to start with bypass enabled and stop after that and it also didn't work. [/quote]

int main(void)
{
    NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos)|(CLOCK_LFCLKSRC_BYPASS_Enabled << CLOCK_LFCLKSRC_BYPASS_Pos ) |
    (CLOCK_LFCLKSRC_EXTERNAL_Enabled << CLOCK_LFCLKSRC_EXTERNAL_Pos);

    NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
    NRF_CLOCK->TASKS_LFCLKSTART = 1;
    while(NRF_CLOCK->EVENTS_LFCLKSTARTED == 0)
    {//do nothing
    }

    NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;

    if(nrf_clock_lf_is_running()){
        NRF_CLOCK->TASKS_LFCLKSTOP = 1; 
        while(nrf_clock_lf_is_running())
        {}
    }
    
    while(1); // It will never reach here?
}

Kenneth

RE: Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

Luis — Mon, 29 Apr 2024 14:43:12 GMT

I only have checked with EXT/BYPASS enabled (i only have a full square wave ext clocK) and with internal RC. Internal RC has no problem. For now It happens evvertime even when not in a debug session. It will happen with a Soft Reset and a Debug Reset but not a Watchdog reset.

I tryed to start with bypass enabled and stop after that and it also didn't work.

RE: Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

Kenneth — Mon, 29 Apr 2024 12:17:31 GMT

You might have found an unknown issue then, and you can confirm this only occurs when using CLOCK_LFCLKSRC_BYPASS_Enabled?

Does the problem only occur when in debug session and/or when you reset from debug session?

Does it happen for instance if you reset from watchdog or soft reset (after a power cycle, not when debug mode)?

What happens if you allways start it with bypass enabled (even when you only want to stop it), so you first (always) start it, and then try to stop it?

Kenneth

RE: Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

Luis — Mon, 29 Apr 2024 04:23:57 GMT

Hello Kenneth,

I tryed to disable the external clock, and still I could not stop it.

Any sugestions?

Best

RE: Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

Kenneth — Tue, 23 Apr 2024 11:42:48 GMT

[quote user="Luis Filipe Rossi"] Any other ideas? Would you be able to replicate it?[/quote]

Just to double check: I assume you have verified that this problem only occurs when using LFCLK source with BYPASS enabled?

If it only occurs with BYPASS enabled, then I am wondering if you can just confirm that the external clock is indeed stopped here also? Or are you still feeding the external clock when you are calling TASKS_LFCLKSTOP? Just wondering if the problem may also be related to the clock is still being provided or not.

I assume you only experience the problem when doing soft reset during debug session, or do you see the problem also for other reset sources, ref:
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/power.html#unique_961802881

Kenneth

RE: Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

Luis — Mon, 22 Apr 2024 15:40:48 GMT

Hello Kenneth,

In this specific test I already disabled the Watchdog. I run this right in the begin of my software

    int watchdog_is_running = 0;
    watchdog_is_running = NRF_WDT->RUNSTATUS;
    printf("WatchDog Status: %d\n", watchdog_is_running);

////EXT CLOCK


      if(nrf_clock_lf_is_running()){
        NRF_CLOCK->TASKS_LFCLKSTOP = 1; 
        while(nrf_clock_lf_is_running())
        {}
      }

The watchdog_is_running returns 0 (so watchdog is not running) but the while(nrf_clock_lf_is_running()) never returns after the stop.

This is somehting I see after reseting the firmware and I previously started the LFCLK as following.

NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos)|(CLOCK_LFCLKSRC_BYPASS_Enabled << CLOCK_LFCLKSRC_BYPASS_Pos ) |
(CLOCK_LFCLKSRC_EXTERNAL_Enabled << CLOCK_LFCLKSRC_EXTERNAL_Pos);

NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
NRF_CLOCK->TASKS_LFCLKSTART = 1;
while(NRF_CLOCK->EVENTS_LFCLKSTARTED == 0)
{//do nothing
}

Any other ideas? Would you be able to replicate it?

RE: Cannot stop LFCLKSTAT from BYPASS EXTERNAL XTAL

Kenneth — Mon, 22 Apr 2024 11:03:02 GMT

Hello,

Do you by any chance have watchdog enabled in your application? When using watchdog a soft reset through the debugger is not sufficient to clear the watchdog, and the watchdog will likely prevent any change to the LFCLK source.

If that is not the problem I suggest to check out the following two errata's:

https://infocenter.nordicsemi.com/topic/errata_nRF52832_Rev3/ERR/nRF52832/Rev3/latest/anomaly_832_132.html
https://infocenter.nordicsemi.com/topic/errata_nRF52832_Rev3/ERR/nRF52832/Rev3/latest/anomaly_832_36.html

Kenneth