NRF9160 DK fails to reconnect to network

[RobertT]

Hello!

 I have the Serial LTE code running on an NRF9160 DK and sending AT commands to publish data to MQTT broker. 

 It happens sometimes that the NRF9160 looses network connection and doesn't go back online. After I do a hardware reset he is back online. On the mosquito broker side I can see in the logs that basically the modem does not answer to the 60s pings sent, so it's offline.  ( " 1621872110: Client trinity has exceeded timeout, disconnecting. " ) 

 At the current moment I am doing hardware resets every hour to keep the modem online but I still get moments when between that hour interval the modem goes offline.

 Any advice would be appreciated. I did put this partially into another topic ( devzone.nordicsemi.com/.../mqtt-return-error-after-24-hours ) but I though of opening a new topic dedicated to the network re-connection process of the nrf9160.

Thank you! 

[Hakon]

Hello,

I can see from your other case that a lot has been tried already. The next thing you can try is capture a modem trace from the disconnect, and then I can pass it on for analysis.

[RobertT]

 Hello, Hakon!

 Please provide some guidance, a weblink, so I can set the logs for modem trace. Is it possible to monitor the dk that I have on site, since that will have valuable information? I am asking this because so far I had the monitored dk connected to my PC and the one on site is on battery.

All the best,

Robert.

[Hakon]

RobertT said:

Please provide some guidance, a weblink, so I can set the logs for modem trace.

This post describes the procedure quite well. If you are unsure how to do it, make sure to follow every step carefully.

[RobertT]

An update: 

- last week I got the new O2 sim card ( for IoT ) and took the set up I had on site and brought it on the bench ( nrf52840 dk communicating over uart to nrf9160 dk ) . Did not change anything on it except for the sim card.

 - I am now into the 5th day of the system running continuously without issues. 

A next step would be to get the same set up with O2 sim card on site and see how it behaves in that area or put the O2 sim card into another set up like this ( just different devices )  on the bench. I will do one of them this week and let you know again what happened.

All the best,

Robert.