Modem Reset Loop Recreation

[DamoL]

Hi, 

I have a feeling we may be experiencing Modem Reset Loop Restrictions on some of our devices, so I want to put in something to our application code so we know and can make the user aware of it. I have added MDMEV notifications and I want to test that we do actually catch it, so I am trying to force the device to get restricted, so far with no luck. 

How can I recreate a modem reset loop restriction? 

According to the documentation - "The modem counts all resets where the modem is not gracefully deinitialized with +CFUN=0" I am using > 1.3.0 so count max is 7. 

Initially, I just tried a hardware reset every time it attempted to make a network connection. After at least 20 resets, it still managed to connect, with no issues. 

I then ran the AT Command passthrough code, so I could manually turn on the modem, and hard reset, just in case my newer code was doing something I wasn't aware of. I did this by subscribing to MDMEV notifications, then putting CFUN=1

AT%MDMEV=1
AT+CFUN=1

After a couple seconds resetting the device, and again, this did not result in any restriction. 

I tried again, this time allowing it to connect to a network, then resetting, and this did not result in a restriction. 

Lastly, I limited the output current on my power supply, so that when I did CFUN=1, the spike in current resulted in a large voltage drop, recreating a brown out reset. Still no luck. 

Any help would appreciated. 

Thanks, 

Damien

[dejans]

Hi Damien,

There might be something in your application which prevents this restriction from occurring. Can you provide more information about your application?
Apart from modem reset loop and activation of reset loop restriction documentation, more information on counting towards restriction can be found in the discussions about reset loop prevention and reset loop.

Best regards,
Dejan

[DamoL]

Hi Dejan, 

I actually managed to do it yesterday, by the AT Command passthrough firmware, turning on the modem with AT+CFUN=1 then pressing the reset button on the nrf Connect Programmer software. 

We have had some units come back to us in a weird state, that we are struggling to recreate. It seems like the modem just becomes unresponsive, and the only fix is a hardware reset/power cycle - I saw information about the reset loop and wondered if it had anything to do with it, so I wanted to put into our firmware, some way of detecting it when it happens, which I have now done, and it works. From my initial testing I am not sure this is the problem though, as it does recover after 30 minutes. 

I think I will open a new ticket on recreating a hard reset/power cycle in software, as a way to fix our issue without units being sent back to us. It is a small number that it happens to, but it does seem to have grown a bit recently. 

[dejans]

Hi,

DamoL said:

I think I will open a new ticket on recreating a hard reset/power cycle in software, as a way to fix our issue without units being sent back to us. It is a small number that it happens to, but it does seem to have grown a bit recently. 

When creating new ticket, please provide  your modem firmware version, application log and modem trace. 

Best regards,
Dejan