sometime host cannot deactivate the LTE when the network registration status is 2

[Siyou]

Hi,

Similar to https://devzone.nordicsemi.com/f/nordic-q-a/57105/nrf9160-modem-stuck-in-searching/231773

We found sometime the LTE cannot be deactivated during the modem is trying to attach or searching network;

It can be reproduced by below steps:

Condition: there is no catM1 network and no NB network(You can assume it is in shielded room)

1), AT+CEREG=5

2), AT+CFUN=21

Wait until the the CEREG notified "+CEREG: 2,....."

3), AT+CFUN=20

Sometime the network registration status cannot chage to 0 even the result of AT+CFUN?  is "+CFUN: 4"

It can be found both catM1(AT%XSYSTEMMODE=1,0,1,0) and NB(AT%XSYSTEMMODE=0,1,1,0) mode.

modem fw version: mfw_nrf9160_1.1.1

[Didrik Rokhaug]

Hi.

When I tested this, I did not see this behavior.

While I do have both NB-IoT and LTE-M network at my home office, I do not have a shielded box. However, my iBasis SIM card does not support my local NB-IoT network, so it will not be able to attach to the network.

I have attached a log from my test, as you can see, +CEREG reports that the modem is offline. The test was done using the at_client from NCS v1.2.0.

Could you provide a modem trace that shows this behavior?

Best regards,

Didrik

Fullscreen modem_disabled_while_searching.txt Download

at%xsystemmode=0,1,0,0
OK
at+cereg=5
OK
at+cfun=21
OK
at+cfun?
+CFUN: 1
OK
+CEREG: 2,"9DD1","01082D66",9,0,0,"11100000","11100000"
at+cfun=20
+CEREG: 0,"9DD1","01082D66",9,0,0,"11100000","11100000"
OK
at+cfun?
+CFUN: 4
OK
at+cereg?
+CEREG: 5,0,"9DD1","01082D66",9,0,0,"11100000","11100000"
OK
at+cgmr
mfw_nrf9160_1.1.1
OK

[Siyou]

Hi,

Please check below our test cmd log and trace based on at_client sample from NCS v1.2.0

2020-04-09T03:34:21.716Z INFO Modem port is opened
2020-04-09T03:34:25.041Z DEBUG modem >> AT+CGMR\x0D\x0A
2020-04-09T03:34:25.064Z DEBUG modem << mfw_nrf9160_1.1.1\x0D\x0A
2020-04-09T03:34:25.067Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:34:31.719Z DEBUG modem >> AT%HWVERSION\x0D\x0A
2020-04-09T03:34:31.734Z DEBUG modem << %HWVERSION: E218\x0D\x0A
2020-04-09T03:34:31.737Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:34:39.576Z DEBUG modem >> AT%XSYSTEMMODE=1,0,1,0\x0D\x0A
2020-04-09T03:34:39.594Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:34:45.594Z DEBUG modem >> AT+CGDCONT=0,"IP","test"\x0D\x0A
2020-04-09T03:34:45.612Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:34:52.345Z DEBUG modem >> AT%XBANDLOCK=2,"1000000000010000001"\x0D\x0A
2020-04-09T03:34:52.361Z DEBUG modem << OK\x0D
2020-04-09T03:34:59.120Z DEBUG modem >> AT%XSYSTEMMODE?\x0D\x0A
2020-04-09T03:34:59.136Z DEBUG modem << %XSYSTEMMODE: 1,0,1,0\x0D\x0A
2020-04-09T03:34:59.138Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:35:07.857Z DEBUG modem >> AT+CEREG=5\x0D\x0A
2020-04-09T03:35:07.871Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:35:14.466Z DEBUG modem >> AT+CFUN=21\x0D\x0A
2020-04-09T03:35:14.510Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:35:30.876Z DEBUG modem << +CEREG: 2,"FFFE","FFFFFFFF",7,0,0,"11100000","11100000"\x0D\x0A
2020-04-09T03:35:34.619Z DEBUG modem >> AT+CFUN=20\x0D\x0A
2020-04-09T03:35:34.639Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:35:41.451Z DEBUG modem >> AT+CEREG?\x0D\x0A
2020-04-09T03:35:41.469Z DEBUG modem << +CEREG: 5,2,"FFFE","FFFFFFFF",7,0,0,"11100000","11100000"\x0D\x0A
2020-04-09T03:35:41.477Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:35:50.938Z DEBUG modem >> AT+CFUN?\x0D\x0A
2020-04-09T03:35:50.957Z DEBUG modem << +CFUN: 4\x0D\x0A
2020-04-09T03:35:50.974Z DEBUG modem << OK\x0D\x0A
2020-04-09T03:35:56.352Z DEBUG modem >> AT+CEREG?\x0D\x0A
2020-04-09T03:35:56.370Z DEBUG modem << +CEREG: 5,2,"FFFE","FFFFFFFF",7,0,0,"11100000","11100000"\x0D\x0A
2020-04-09T03:35:56.380Z DEBUG modem << OK\x0D\x0A

trace-2020-04-09T03-33-52.630Z.bin

[Didrik Rokhaug]

Hi, and sorry for the late reply.

Sadly, your modem trace is empty, so I can not read anything from it. A proper modem trace easily reaches a size of several hundred kilobytes if not more, and with the LTE stack enabled it should grow with several kilobytes per second.

Could you try to capture a new trace?

Make sure that CONFIG_BSD_LIBRARY_TRACE_ENABLED=y is set, and that you have issue AT%XSYSTEMMODE=1,2

[Didrik Rokhaug]

I have had a talk with the modem team, and they believe that the behavior you are seeing is because of a bug in the modem that leads to the CEREG stat not being updated.

AT+CFUN? correctly returns that the modem is offline, while AT+CEREG? has not been updated to show that the modem is offline. They are looking into the root of the bug.

[Siyou]

Hi

This issue still exist on mfw_nrf9160_1.2.0, is there any update or workaround?

[Didrik Rokhaug]

Hi, and sorry for the late reply.

The bug has been identified and fixed and will be part of the next modem firmware release (it did not make it into mfw v1.2.0).

Best regards,

Didrik