Requirements and application limitations
Following are some of the requirements and limitations of the application while running this module:
The application must not call the
The LwM2M carrier library initializes and uses the Modem library. This library is needed to track the modem FOTA states.
The LwM2M carrier library registers to receive several AT event reports using the AT monitor library. The following notifications must not be deregistered by the application:
SMS events (AT+CNMI).
Packet Domain events (AT+CGEREP).
Extended signal quality events (AT+CESQ).
ODIS events (AT+ODISNTF).
Universal Integrated Circuit Card events (AT%XSIM).
Network Time events (AT%XTIME).
Modem Domain events (AT%MDMEV).
Report Network Error Codes events (AT+CNEC) - EPS Session Management events are used by the LwM2M carrier library. The application may enable or disable EPS Mobility Management events.
Network Registration Status events (AT+CEREG) - Notification Level 4 is used by the LwM2M carrier library. The application can increase this level but must not decrease it.
If the application wants to use eDRX, it must enable mode 2, since the LwM2M carrier library requires the unsolicited result code.
The application must prioritize the LwM2M carrier library requests to connect and disconnect from the network.
The LwM2M carrier library uses the TLS socket for FOTA.
The LwM2M carrier library uses both the DTLS sessions made available through the modem. Therefore, the application cannot run any DTLS sessions.
The LwM2M carrier library provisions the necessary security credentials to the security tags 25, 26, 27, 28. These tags must not be used by the application.
The CA certificates that are used for out-of-band FOTA must be provided by the application. Upon initialization, the application will receive the event
LWM2M_CARRIER_EVENT_CERTS_INIT(see LwM2M carrier library events). Although the certificates are updated as part of the nRF Connect SDK releases, you must check the requirements from your carrier to know which certificates are applicable.
The LwM2M carrier library uses the following NVS record key range: 0xCA00 - 0xCAFF. This range must not be used by the application.
The following library sizes are reported in the Changelog:
Library size (binary): This shows the standalone size of the library. This size includes all objects since the library is not linked. This size will change when linking the library to an application.
Library size (reference application): This size shows the total memory impact of enabling the LwM2M carrier library in the nRF9160: LwM2M carrier sample. This size accounts for the library, abstraction layer and the associated heap and stack requirements. It also includes all the resources for all the dependencies, except Modem library. See Application integration for more information.
Enabling the LwM2M carrier library into the nRF9160: LwM2M carrier sample serves only as a reference. The increase in memory size due to the inclusion of the LwM2M carrier library depends on the application that it is being integrated into. For example, an application such as the nRF9160: Asset Tracker v2 already uses several libraries which the LwM2M carrier library depends on. This makes the added memory requirement considerably smaller.