Reset loop and XPOFWARN

[Vincent44]

Hello,

On my nRF9160 custom device, I have enabled XPOFWARN to automatically switch off the modem in case the voltage gets too low. It's working fine.

This case happens when my device is not installed, as it is store without its antenna. In this situation, the TX power is increased which leads to battery voltage dropping (because my battery is not strong enough). The XPOFWARN does a great job at stopping the modem, preventing the battery to drop even lower, which would lead to brownout reset.

I was wondering if this case can lead to a reset loop ? My device tries to connect to the network every 15min. But if the battery is low, or if the antenna is removed, the modem will automatically be switched off.

The reset loop trigger after 7 resets. Is there any time restriction on this ? Is it 7 reset in 1h/day ? Of is it simply 7 reset in a row, without any proper switch off ?

Also, is there a way to read if the device is in the reset loop ? Or does it only work with %MDMEV ?


Thanks.

[Charlie]

Hi Vincent,

I was wondering if this case can lead to a reset loop ? My device tries to connect to the network every 15min. But if the battery is low, or if the antenna is removed, the modem will automatically be switched off.

No, reset loop only counts the modem activations that lead to a reset without deinitializing the modem between the activations, and it does not count power supply caused brown out.

The reset loop trigger after 7 resets. Is there any time restriction on this ? Is it 7 reset in 1h/day ? Of is it simply 7 reset in a row, without any proper switch off ?

No time restriction, but keep in mind the counter will reset to zero in any of the following condiction:

1. when modem deinitialization with +CFUN=0 is triggered before the predefined limit is reached.

2. after modem initialization when a reset has not occurred in 60 s.

3. If the modem is activated after initialization and registration to network succeeds before 60 s has passed.

Also, is there a way to read if the device is in the reset loop ? Or does it only work with %MDMEV ?

Yes, you will get  %MDMEV: RESET LOOP nottificiton if you set AT%MDMEV=1.

The above information is available in the white paper:

Modem Reset Loop Restriction (nordicsemi.com)

Best regards,

Charlie