Drawing high current without any application functionalities.

[manjiw]

We are using a custom nrf52832 HW configuration and the device is entering a state where it's drawing approximately 3mA without any obvious application layer functionality. 
It is not advertising any Bluetooth information, nor is it logging any information to the flash through our application. 

We are finding it difficult to recreate this issue consistently although we have managed to do so a handful of times. This is how we have managed to find out the above details. 

Any suggestions on steps to further uncover the root of the issue? 

[Elfving]

Hello,

I will have to get back to you on this next week.

Regards,

Elfving

[manjiw]

A quick update from my end. This is so far the diagnosis and approach we're taking. 

Observed symptoms of a ‘dead’ device:

1. No Bluetooth information being advertised

2. No application layer functionality

3. Current draw of 3-4mA

4. Voltage from battery dropping over time

   1. Once disconnected from battery, the battery voltage will readjust to a ‘healthy’ potential

Potential reasons for observed symptoms:

1. Soft Device being disabled

2. Timers being disabled

3. & 4. If both the Soft Device and the Timers are disabled the firmware will enter a constant loop of nrf_pwr_mgmt where (as tested) approx. 4mA of current will be drawn and the voltage output from the battery will drop.

Potential solution to the issue:

• Implementing a watch dog which will timeout if it is stuck in the nrf_pwr_mgmt loop.

Any other insights are welcome. Cheers. 

[Elfving]

Hello Manjitha,

In general, a watchdog sounds like a good idea.

Have you checked if this might be due to any assert? I.e., by making a led blink in the hard fault handler, or anything similar?

Is disabling Softdevice and timers any part of your application?

Have you tested if this is happening on a DK as well? 

Regards,

Elfving

[manjiw]

Hey, 

Thanks for your suggestions. As for now we've implemented a watchdog and improved our logging system. 

We were not able to recreate the issue again, which tells me it is a very rare firmware lock-up. Softdevice and timers get disabled to carry out certain operations but they return to enabled states afterwards. Some form of lockup could occur in between these operations. 

Regardless, we will keep monitoring this issue and see if the problem persists in the future. 

Cheers for your help. 

[Elfving]

No problem at all!

Regards,

Elfving