When the battery is low, the program freezes and the watchdog cannot be reset. J-link can't read the device

[SOK_LiWang]

hellow

I made a wearable device using nRF52840. 3.7V lithium battery power supply. The software adopts NCS V2.6.0. I found a problem that when my device is working at full speed and the battery level drops to 2.9V, the device stops working. nRF52840 will also stop working, after the battery is fully charged, nRF52840 will not restart work, it seems that the program is stuck somewhere. I want to use J-link to send nrfjprog.exe --reset, then J-link can't read the device either. The device will not reset until the battery is rewelded. A single channel EEG collection device I made, nRF52832, did not have this problem. Is there a problem with my device tree or config configuration? And please help me. Thank you so much.

sok

[JONATHAN LL]

Hi Sok, 

Can you measure the voltage on the VDD pin close to the SoC, so that you can see what is happening at the chip. Best is to use a scope and capture the issue that is happening. 


Also can you disable pin reset and see if the issue still happens. 


And what you explain sounds like a BOR\POR reset loop, but this can only happen if the voltage is under brown out levels, so under 1.8V at least. And if the battery has a high seires resistance and is close to empty or bad in any way. 


Regards,
Jonathan