How to recover a nRF9160 from sporadic ENETDOWN

[Achim Kraus]

Using a Thingy!91 (v1.0.0 and v1.4.0, firmware 1.2.3, 1.2.7) I get sometimes (every couple of days) a ENETDOWN when sending data out. Before that ENETDOWN, the device was usually able to exchange 100 and more UDP messages.

Currently I do a "sys_reboot(SYS_REBOOT_COLD)", but I'm wondering, if there are less massive ways to recover.   

I found other questions, but I'm still struggling to see an "useful" answer. e.g.

https://devzone.nordicsemi.com/f/nordic-q-a/57642/nrf9160-lte-modem-documentation

but the link at the end, ends in "NOT FOUND".

So, what is the recommended way to recover from ENETDOWN?

[Albrecht Markus Schellenberger]

Hello Achim,

Achim Kraus said:

So far, that works. Lets see, if it still works in 2-3 weeks :-).

Thanks for your feedback :-)

Achim Kraus said:

Though this case is rare in reality, I'm still not that sure. Anyway, that are my results so far:

What is it you are not sure about?

Regards,

Markus

[Achim Kraus]

> What is it you are not sure about?

I'm not sure, if this is the only root cause and reopen the socket is always the fix for the ENETDOWN.

My test was done with plugin an external lte-antenna and then cover that or remove the antenne (leave the plugtail in the modem). That causes a couple of network reconnects, but even with that, only a few showed also the ENETDOWN.

So, lets see, if that "lost network" is the only cause of the ENETDOWN and the failing socket.

(And in too many cases, after fixing a bug, the next bug will show up. Same as in soccer ;-) ):