NRF52 Watchdog not resetting

[jonas.woerner]

Hi,

Currently I am trying to implement Watchdog functionality into my Project.

I have the followowing problem:

I use the Nordic WatchdogTimer.h and instance the class with 1s in the constructor.

now, if I just do a 'while(1);' the code succesfuly resets after about 1 Second.

But If I dont use a while loop, it does not reset, even if I dont use the WDT::Kick() function..?!

I think I altered some of the nrf52_bitfields.h parameters, but I dont remember which ones, so maybe thats the cause, but what could it be?

Its really strange that it resets on a while loop, but not without it and without WDT::Kick()

Thanks,

jonas

[twihtronics]

have you attempted to run a diff between your modified bitfield.h and the standard one? Not sure if this has anything to do with you issue but it is a start. Or may try using the watch dog driver assuming you are using sdk15.2 or above.

[jonas.woerner]

I didnt find an unmodified version of the bitfield.h, the only one I found had completly different defines in it..

I am using SDK14 I think, so I guess thats not an option.. however, what does it do differently from the old WDT library?

[Einar Thorsrud]

Hi,

The only way to prevent the watchdog from resetting is feeding it (or going to sleep if the WDT is configured to pause in that case - which is usually not a good idea). Can you upload the minimal code you are using to test this? That way we can see if we spot something odd.

[jonas.woerner]

yep, here I have the ultra minimal code, which still shows this strange behaviour.

#include "RTT/SEGGER_RTT.h"
#include "WatchdogTimer.h"
int main() {
SEGGER_RTT_Init();
SEGGER_RTT_WriteString(0,"startup\n");
WatchdogTimer WDT(3);

  while(1) {
    SEGGER_RTT_WriteString(0,"looping\n");
    Thread::wait(1000);
    while(1);
  }

}

when used exactly like this the code resets after some time (I noticed its not the WDT timeout, but rather random when it resets...)

if you remove the while(1); the code will print "looping" all the time without restarting.

my guess is still that it has something to do with the bitfields file, because thats the only thing I modified. But I dont find this file anywhere... only versions that are different from mine.

[jonas.woerner]

I just realized that my WatchdogTimer.h is for NRF51xx boards... here is the code:

WatchdogTimer::WatchdogTimer(float seconds)
{
    //Configure watchdog timer
    //HALT_Pause: Pause watchdog when debugger stops chip
    //Sleep_Run: Continue running watchdog when chip sleeps
    NRF_WDT->CONFIG = (WDT_CONFIG_HALT_Pause << WDT_CONFIG_HALT_Pos) | ( WDT_CONFIG_SLEEP_Run << WDT_CONFIG_SLEEP_Pos);
    
    //Set watchdog timeout (seconds * clock cycle)
    NRF_WDT->CRV = seconds * (float)NRF_CLK_RATE;
    
    //Enable reload register 0
    NRF_WDT->RREN = WDT_RREN_RR0_Enabled << WDT_RREN_RR0_Pos;
    
    //Start the watchdog timer
    NRF_WDT->TASKS_START = 1;
}

void WatchdogTimer::kick()
{
    //Reload register 0
    NRF_WDT->RR[0] = WDT_RR_RR_Reload;
}

now im wondering what I have to change so it would work with my NRF52.. but I will do some research

[Einar Thorsrud]

This is not SDK code from Nordic (here is no WatchdogTimer.h file in the SDK). Where does this come from?

[jonas.woerner]

yeah, I just realized that, my bad. I think I got it somewhere from git, im not 100% sure where tho.

however, I read the documentation ( http://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.nrf52832.ps.v1.1%2Fwdt.html ) and from what I can tell this code should work... all registers are set correctly. so whats the mistake?

[jonas.woerner]

I just tested:

int main()
{
  static const uint16_t NRF_CLK_RATE = 32768; //32KHz
  NRF_WDT->CONFIG = 0x00001001;
  NRF_WDT->CRV = 2 * NRF_CLK_RATE;
  NRF_WDT->RREN = 0x111111111;
  NRF_WDT->TASKS_START = 1;
  SEGGER_RTT_Init();
  SEGGER_RTT_WriteString(0, "startup\n");

  while (1)
  {
    SEGGER_RTT_WriteString(0, "looping\n");
    Thread::wait(1000);
  }
}

It does not work.

[Einar Thorsrud]

Hi,

There are a few issues with your code, but none that should prevent it from working. I have fixed the writes to the WDT registers and modified the code to match the normal nRF5 SDK like this:

int main(void)
{
    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();
    NRF_LOG_INFO("Temperature example started.");

    static const uint16_t NRF_CLK_RATE = 32768; //32KHz
    NRF_WDT->CONFIG = 0x00000009;
    NRF_WDT->CRV = 2 * NRF_CLK_RATE;
    NRF_WDT->RREN = 0x11111111;
    NRF_WDT->TASKS_START = 1;

    while (1)
    {
        NRF_LOG_INFO("looping");
        nrf_delay_ms(1000);
    }
}

This gives the expected log output:

<info> app: Temperature example started.
<info> app: looping
<info> app: Temperature example started.
<info> app: looping
<info> app: looping
<info> app: Temperature example started.
<info> app: looping
<info> app: looping
<info> app: Temperature example started.
<info> app: looping
<info> app: looping
<info> app: Temperature example started.
<info> app: looping
<info> app: looping
<info> app: Temperature example started.
<info> app: looping
<info> app: looping
<info> app: Temperature example started.
<info> app: looping
<info> app: looping
<info> app: Temperature example started.
<info> app: looping
<info> app: looping

Please also note that the SDK includes a WDT example which uses the WDT driver, providing a high-level API that is tested and verified by us (Nordic).

[jonas.woerner]

yehaa, its working!

I still dont know why the WatchdogTimer.h does not work, but I will just do it this way now.

my first try to do it without the included file would have worked, if I wouldnt have been so stupid and accidentally use 0x00001001 instead of 0b00001001.

So thanks for helping me out!

Jonas

[jonas.woerner]

well.. I discovered something strange... when I set CONFIG to 0x00000009 it will work. If I try to set it to 0x00 it wont work?! also, I noticed that for the CONFIG=... it will take a power cycle for the change to get applied, is that intentionally?

[Einar Thorsrud]

Hi,

What do you mean by saying that it won't work when CONFIG is set to 0? In that case the WDT will pause when in sleep or haltet by a debugger, so if your current test code does that, then you should not expect to see a reset.

Regarding changes to the CONFIG register, that must always be done before the WDT is started by writing to TASKS_START. Once it is started it cannot be reconfigured, and the only way to stop it (so that it can be reconfigured again) is with a reset. This is intentional behavior, as it prevents a malfunction system to accidentally reconfigure the SoftDevice, potentially preventing a WDT reset.

The WDT chapter in the PS specifies it like this:

The watchdog must be configured before it is started. After it is started, the watchdog’s configuration registers, which comprise registers CRV, RREN, and CONFIG, will be blocked for further configuration.