building at_client for nb-iot on nrf9160-dk

[paul_tanner]

select at_client folder

west build -b nrf9160dk_nrf9160ns -p

shows this warning

```

warning: The choice symbol LTE_NETWORK_MODE_NBIOT (defined at
/Users/paul_tanner/Nordic/nrfsrc/ncs/nrf/lib/lte_link_control/Kconfig:152) was selected (set =y),
but no symbol ended up as the choice selection. See
docs.zephyrproject.org/.../CONFIG_LTE_NETWORK_MODE_NBIOT.html and/or
look up LTE_NETWORK_MODE_NBIOT in the menuconfig/guiconfig interface. The Application Development
Primer, Setting Configuration Values, and Kconfig - Tips and Best Practices sections of the manual
might be helpful too.```

```

paul_tanner@iMac at_client % ls

CMakeLists.txt build_nrf9160dk_nrf9160

README.rst build_nrf9160dk_nrf9160ns

at_client.hex prj.conf

at_client_nbiot.hex sample.yaml

build src

```

note there is no Kconfig file here

when running the resulting binary

```

AT%XSYSTEMMODE?
%XSYSTEMMODE: 1,0,1,0

```

Not surprisingly it does not connect to any NB-IOT access point.

My questions are:

1. do I need a Kconfig for NB-IOT?

2. can I use the same firmware versions for this and LTE/M?

Thx. 

[paul_tanner]

Sorry, forgot to say that LTE_NETWORK_MODE_NBIOT=y is set in prj.conf

[Didrik Rokhaug]

Hi,

The CONFIG_LTE_NETWORK_MODE_* Kconfig symbols are for the lte_link_control library.

As the lte_link_control library is used for configuring the modem (specifically the LTE link) from an application running on the application core, and the purpose of the at_client is that you can configure the modem manually, the at_client does not use the lte_link_control library.

As the lte_link_control library is not enabled, the Kconfig symbols it uses will not be defined. That is the reason for the build warning (in general, I recommend that you treat Kconfig warnings as errors).

Instead, when you use the at_client sample, you must configure the modem manually. To set the system mode to NB-IoT, you can use AT%XSYSTEMMODE=0,1,x,0, where x is 1 if you also want GPS, 0 otherwise. Note that the modem must be offline (CFUN=4 or 0) when you set the system mode.

You can then use AT+CFUN=0 to store the configuration in permanent memory.

 

1. do I need a Kconfig for NB-IOT?

 Only when using the lte_link_control library.

 

2. can I use the same firmware versions for this and LTE/M?

 You can use the same modem firmware for both modes. If you do not set the mode, LTE-M is the default.

If you are using the lte_link_control library, the default is controlled by the Kconfig options. But, the system mode can also be changed at run-time by the application.

And, again, to be clear: The at_client sample does not use the lte_link_control library, and requires you to configure the modem manually.

Best regards,

Didrik

[Didrik Rokhaug]

It is a bit hard to say for sure without seeing more of the log, but at the moment those commands were sent, the modem was searching for an NB-IoT network:

+CEREG: 5,2,"FFFE","FFFFFFFF",9,0,0,"11100000","11100000", The "2" means that it is searching, the "9" is NB-IoT, the F'es indicate that it has not found any cells yet.

But it has not found any signal:

+CESQ: 99,99,255,255,255,255

This is typical of an "out of coverage" scenario, although there is a chance that the device would be able to find a network if left searching for a longer period of time.

But, if the lte_link_control library times out, and you have not changed the timeout value, it has already been searching for 10 minutes. That should have been more than enough in most cases.

A few months ago we had another customer report issues with Vodafone's NB-IoT network in the UK. I know they have been doing some improvements since then, but they might not have gotten to your area yet. Your Regional Sales Manager might know more about the current situation. If you do not know how to contact your RSM, you can send me a private message with your location, and I will provide the contact information.

You can read more about the other customer's issue here: https://devzone.nordicsemi.com/f/nordic-q-a/64454/bad-nb-iot-signal-strength-in-uk

[paul_tanner]

Thanks Didrik,

I know that the NB-IoT coverage is patchy.  Based on your observations i think it might be worth moving to somewhere else.  No full coverage map is available but I have obtained one for my immediate area.

Will report back later and maybe capture more logging.

[paul_tanner]

I did another test with the asset tracker

prj.conf includes:

```

CONFIG_LTE_PDP_CONTEXT="0,\"IP\",\"lpwa.vodafone.iot\""
CONFIG_LTE_NETWORK_MODE_LTE_M_GPS=n
CONFIG_LTE_NETWORK_MODE_NBIOT_GPS=y
CONFIG_LTE_LEGACY_PCO_MODE=n
CONFIG_LTE_PSM_REQ_RPTAU="00000110"
CONFIG_LTE_PSM_REQ_RAT="00000010"

```

Moved to a location where vodafone says there's a good NB-IoT service

```
[00:00:00.322,387] [0m<inf> asset_tracker: Connecting to LTE network.[0m
[00:00:00.329,101] [0m<inf> asset_tracker: This may take several minutes.[0m
at%xsystemmode?

%XSYSTEMMODE: 0,1,1,0
OK

```

It's looking for an NB-IoT service

```

+CEREG: 2,"FFFE","FFFFFFFF",9,0,0,"11100000","11100000"
[00:01:53.916,809] [0m<inf> asset_tracker: LTE cell changed: Cell ID: -1, Tracking area: 65534[0m
[00:01:53.925,720] [0m<inf> asset_tracker: PSM parameter update: TAU: -1, Active time: -1[0m
at+cereg?
+CEREG: 5,2,"FFFE","FFFFFFFF",9,0,0,"11100000","11100000"
OK

```

time passes...

```

[00:10:00.385,467] [0m<inf> lte_lc: Network connection attempt timed out[0m
+CEREG: 0,"FFFE","FFFFFFFF",9,0,0,"11100000","11100000"
[00:10:00.412,078] [0m<inf> lte_lc: Using fallback network mode[0m
at%xsystemmode?

%XSYSTEMMODE: 1,0,1,0
OK

```

It's now looking for an LTE/M service - which it won't find.

Ideally it should keep looking for NB-IoT and I think I told it to do so:

CONFIG_LTE_NETWORK_MODE_LTE_M_GPS=n
CONFIG_LTE_NETWORK_MODE_NBIOT_GPS=y

Is that not correct?

[Didrik Rokhaug]

Yes, you have configured it correctly to look for NB-IoT.

However, the LTE link control library will by default try the other network mode as a fallback, if the device has not been able to connect to the network after a given time.

You can disable the fallback mechanism by setting CONFIG_LTE_NETWORK_USE_FALLBACK=n in prj.conf, and you can change the timeout value with CONFIG_LTE_NETWORK_TIMEOUT (default is 600 seconds).

[paul_tanner]

OK.  I think the problem was that we were out of range.

The next test was from somewhere nearer to a mast.

Now we get:

```

+CEREG: 5,"1BE8","0029FF0B",9,,,"11100000","00101000"

[00:02:01.235,626] [0m<inf> asset_tracker: Connected to LTE network.[0m

[00:02:01.242,523] [0m<inf> asset_tracker: Network registration status: Connected - roaming[0m

[00:02:01.251,220] [0m<inf> asset_tracker: PSM parameter update: TAU: 28800, Active time: -1[0m

[00:02:01.479,919] [1;33m<wrn> [0m

[00:02:01.719,909] [1;33m<wrn> date_time: getaddrinfo, error: -11[0m

[00:02:01.928,924] [1;33m<wrn> date_time: getaddrinfo, error: -11[0m

[00:02:02.151,916] [1;33m<wrn> date_time: getaddrinfo, error: -11[0m

[00:02:02.408,935] [1;33m<wrn> date_time: getaddrinfo, error: -11[0m

[00:02:02.415,344] [1;33m<wrn> date_time: Not getting time from any NTP server[0m

[00:02:02.422,851] [0m<inf> asset_tracker: DATE_TIME_NOT_OBTAINED[0m

[00:02:02.429,290] [0m<inf> asset_tracker: Connecting to cloud, attempt 1 of 8[0m

[00:02:02.436,859] [0m<inf> asset_tracker: Cloud connection request sent.[0m

[00:02:02.443,939] [0m<inf> asset_tracker: Connection response timeout is set to 30 seconds.[0m

[00:02:02.452,789] [0m<inf> asset_tracker: CLOUD_EVT_CONNECTING[0m

[00:02:03.655,975] [0m<dbg> nrf_cloud_transport.nct_connect: getaddrinfo failed -11[0m

[00:02:03.663,970] [0m<inf> asset_tracker: CLOUD_EVT_CONNECTING[0m

[00:02:03.670,166] [1;31m<err> asset_tracker: Failed to connect to cloud, error -3[0m

[00:02:03.678,070] [1;31m<err> asset_tracker: Network error, check cloud configuration[0m

[00:02:03.686,279] [1;31m<err> asset_tracker: Device will reboot in 300 seconds[0m

```

I think we got a connection but there was another config issue.

could it be that setting the APN

```

CONFIG_LTE_PDP_CONTEXT="0,\"IP\",\"lpwa.vodafone.iot\""

```

Did not work.

I tried 

```

AT+CGDCONT?

OK

```

This suggests that it is not set.  In that case any call requiring a connection would likely fail.

[Didrik Rokhaug]

I have not tried to set the APN manually lately, the modem usually figures that out automatically based on the network, so my memory there is a bit rusty. I will run some tests tomorrow and come back to you then.

But, it could also be that the network does not support ePCO.

Could you try to add CONFIG_LTE_LEGACY_PCO_MODE=y to the prj.conf?

And are you building with SES? If so, you must re-open the project, or use 'Project -> Run CMake...' for changes to prj.conf (or other configuration files) to take effect.

[paul_tanner]

Looks like there is a dependency where you need

CONFIG_LTE_PDP_CMD=y

for 

CONFIG_LTE_PDP_CONTEXT=...

to be allowed.

It's still not working but at lease now AT+CGDCONT? produces the right result.

Some other issue is causing it to give up after only one connection attempt.

[Didrik Rokhaug]

From your last log, it looks like you are able to connect:

+CEREG: 5,"1BE8","0029FF0B",9,,,"11100000","00101000"

[00:02:01.242,523] [0m<inf> asset_tracker: Network registration status: Connected - roaming[0m

Although the DNS lookup failes:

[00:02:01.719,909] [1;33m<wrn> date_time: getaddrinfo, error: -11[0m

[00:02:03.655,975] [0m<dbg> nrf_cloud_transport.nct_connect: getaddrinfo failed -11[0m

It might be that the network does not support ePCO. At least, that has been the case in other NB-IoT networks with DNS problems.

You can use "legacy" PCO instead by setting CONFIG_LTE_LEGACY_PCO_MODE=y

[paul_tanner]

Thanks. That certainly moved things forward.  So now it does get data/ time.

We then found a whole lot of other issues which I have posted separately.

devzone.nordicsemi.com/.../initiation-problem-on-vodafone-with-nb-iot-from-nrf9160-dk