application: serial_lte_modem: Allow auto-connect for NIDD

[junqingzou]

For the use case of FOTA over NIDD with lwm2m_carrier,
.Enable auto-connect NIDD after FOTA image is applied.
.Enable auto-connect NIDD on all kinds of reset.
.Add AT#XCARRIER="auto-connect","read|write"[,<auto-connect-flag>] to control YES/NO of auto-connect.

Dependence: libmodem v2.4.2

UPDATE: the solution has been expanded to support both U-bind and N-bind for LwM2M_Carrier.

[junqingzou]

This PR is created for the required behavior in verifying FOTA over LwM2M with NIDD binding in SoftBank network.
DNM for work in progress.

[NordicBuilder]

Test specification

CI/Jenkins/NRF

• Integration Platforms

CI/Jenkins/integration

Test Module	File based changes	Manually selected	West overwrite
test-fw-nrfconnect-nrf-iot_serial_lte_modem	X

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[NordicBuilder]

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[junqingzou]

Hi @mgolu, is auto-connect to NIDD network acceptable to your customers?
We need it to complete FOTA over NIDD sequence in time.

[mgolu]

Hi @mgolu, is auto-connect to NIDD network acceptable to your customers? We need it to complete FOTA over NIDD sequence in time.

Overall this will work, since the auto-connect to NIDD is configurable via the new XCARRIER command.

[junqingzou]

Hi @mgolu, is auto-connect to NIDD network acceptable to your customers? We need it to complete FOTA over NIDD sequence in time.

Overall this will work, since the auto-connect to NIDD is configurable via the new XCARRIER command.

The point is by default auto-connect is eanbled in the setting page, which is behavior change of SLM with NIDD.

[wiba-nordic]

This seems like something that deserves a changelog entry, so remember to add one after this is no longer work in progress.

[VTPeltoketo]

acronym NIDD, which words it comes from?

[junqingzou]

acronym NIDD, which words it comes from?

Non-IP Data Delivery (3GPP R13~)

[wiba-nordic]

I believe this needs a changelog entry for the added AT command.

[kacperradoszewski]

How about extending this functionality to IP context as well? I don't see why this should be restricted to NIDD only, because the binding does not really affect the FOTA sequence and it would be quite convenient to reconnect automatically over UDP as well.

Ther reason that we don't want to support IP network is due to: (1) PDP Context activation normals needs network-specific configuration and use authentication (2) Don't want to change behavior when SLM is built withour LwM2M_Carrier

If there is need to configure the PDP context, the user can always disable auto-connect and use AT commands to do so as they would do until now. I don't see why SLM would have specific handling for Non-IP binding, which in the LwM2M Carrier library's case is definitely the less common choice. If it's more convenient to set up the context in the code for NIDD, I would simply restrict that section of code to be conditional on CONFIG_LWM2M_CARRIER_SERVER_BINDING_N, but I do find it slightly odd for the SLM to have what seems like application-specific implementation. Setting the functional mode of the modem to 1 (CFUN=1) can apply regardless of the binding, and that can be made dependent on CONFIG_SLM_CARRIER, so this wouldn't affect the behaviour when SLM is built without carrierlib.

[junqingzou]

How about extending this functionality to IP context as well? I don't see why this should be restricted to NIDD only, because the binding does not really affect the FOTA sequence and it would be quite convenient to reconnect automatically over UDP as well.

Ther reason that we don't want to support IP network is due to: (1) PDP Context activation normals needs network-specific configuration and use authentication (2) Don't want to change behavior when SLM is built withour LwM2M_Carrier

If there is need to configure the PDP context, the user can always disable auto-connect and use AT commands to do so as they would do until now. I don't see why SLM would have specific handling for Non-IP binding, which in the LwM2M Carrier library's case is definitely the less common choice. If it's more convenient to set up the context in the code for NIDD, I would simply restrict that section of code to be conditional on CONFIG_LWM2M_CARRIER_SERVER_BINDING_N, but I do find it slightly odd for the SLM to have what seems like application-specific implementation. Setting the functional mode of the modem to 1 (CFUN=1) can apply regardless of the binding, and that can be made dependent on CONFIG_SLM_CARRIER, so this wouldn't affect the behaviour when SLM is built without carrierlib.

I get your point. Something special with LwM2M_Carrier integration is that you enabled the PDN library in the overlay. This means that customer can add extra CONFIG defined by the library to configure LTE connection, upon libmodem is initialized by SLM main(). Then I'll use CONFIG_SLM_CARRIER to enclose the auto connection logic, which will contain CFUN=1 only.

New solution tested good with Leshan (U-binding) and SoftBank IoTPF (N-binding) with two different overlays.

[kacperradoszewski]

Nice and useful improvement, thanks 👍

[VTPeltoketo]

Why the SYSTEMMODE setting has to be under CONFIG_LWM2M_CARRIER_SERVER_BINDING_N?

[junqingzou]

Why the SYSTEMMODE setting has to be under CONFIG_LWM2M_CARRIER_SERVER_BINDING_N?

Because modem only support NB-IoT for NIDD connection.