URGENT : NRF52840 hanging up after working for some time!!!

[kaushalyasat]

Hi,

THIS IS AN URGENT REQUEST. PLEASE HELP ASAP.

After deploying our sensors based on nRF52840 running coap client on OpenThread and powered by 3V 2032 Lithium coin cell, we have noticed that two out of about 50 sensors just not sending data to the host. One of the sensors we know has hung up with no response to the button push and lo LED indication. The other have the characteristics of it, but not yet confirmed by the client. The issue is not immediate, some like couple weeks, some couple of days. We have seen two of our sensors, which are being tested in our lab, to hang up as well. We dont have an external watchdog. Not sure if the internal watchdog is enabled.

Once the sensor hangs up, you can make it come back alive by power cycling. 

Now we have an external 32k oscillator in our design, which showed stopping after some time probably due to capacitor loading not being correct. So we revert to internal oscillator, which seem to solve the issue. That is how these sensors been working so far and release to customers. But the external oscillator and two loading caps exist in the PCB. I dont know if this can be an issue if we use HFINT internal oscillator. 

We have enabled the internal oscillator by the following in the prj.conf.

CONFIG_CLOCK_CONTROL=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=n

We have not done any calibrations for the HFINT. 

So these are my questions.

1. What possible causes could be there for the hang-up of nRF52840? As mentioned, it is powered by a 3V coin cell, which is not discharged and running off the internal HFINT oscillator. 

2. Can the 32k external oscillator being present in the sensor affect the stability of HFINT oscillator?

3. Is the way in which we have enabled the internal oscillator good enough? Do we need to do any calibrations for it?

4. Can the internal WDT restart the HFINT oscillator, if it has stopped for whatever reason?

5. How to enable, load and hit the internal WDT from application FW?

Cheers,

Kaushalya

[kaushalyasat]

Hi Stian,

Ok, I see. Unfortunately the two hung-up sensors are packaged to be send to you, so I cant run this anymore. You can try when you get the devices, hopefully soon. I have the other sensors which showed this behavior with me, but with WDT fw. So I dont know if if the WDT will heal the issue. 

I am will do an IR test for the batteries on the failed ones to see how bad the IR is.

Cheers,

Kaushalya

[Stian Røed Hafskjold]

Hello,

I was able to power the devices from a power analyzer without resetting them. And I can clearly see that they are in system ON idle, consuming around 2 uA and doing the LFRC clock calibration every 4 seconds. So everything looks normal. Except that it is not advertising.

I don't think there are any reasons to suspect any battery issues, or any hardware issues, as the CPU is waking up to calibrate the LFRC, which means that the LFRC, RTC, CPU interrupts, etc, are working as normal. So this looks to me like a software issue.

I will continue to investigate, but it would be nice if you could share your software project, so I can build the code here. Maybe zip it and send it in a PM or similar. Thanks.

Best regards,
Stian

[kaushalyasat]

Hi Stian,

All your support much appreciated. That is a good news. How could we know its doing the LFRC clock calibration? Just by looking at the 4 sec current draws?

To send the project, by PM, you mean as a personal message ?

Cheers,

Kaushalya

[WENDELL V BOYD]

Kaushalya,

You should be able to move the DevZone ticket to 'Private' this will allow you to post any more sensitive or confidential materials such as your code directly to the Nordic team. Regards.

[kaushalyasat]

Thanks Wendell, I tried looking for ways to move this to private, but couldn't find. I can move my original post, but there is no 'private' section in the list. Could you please elaborate a bit?  

Thanks,

Kaushalya