nRF52840 Zephyr - External LTE-M modem, offloading and LwM2M

[newUser]

Hi,

On our custom nRF52840 board, we have an external LTE-M modem.

We would like to eventually use this modem to send data over the network, including LwM2M.
What is the best way to achieve this? I have some experience with the nRF9160, in which socket offloading is used.

Is this the recommended method here as well? Can the existing LwM2M implementation use that offloading driver without problem?
We still need to be able to interface with the modem in the application layer as well.

Please let me know your thoughts!

[Martin Lesund]

Hi newUser,
What are you planning to send between the nrf52 and the nrf91?
 You could e.g. run something like the Serial LTE modem application on the nRF91 and handle all the AT command communication on the nrf52 necessary for your functionality.
However it does not have all the features supported yet as you would if you run your application on the application side in the nrf91, using sockets etc.

So it depends a bit what you plan to use the nrf91 for and what you are going to send.
We can make this case private as well if there is sensitive information.

[newUser]

Hi Martin, thank you for your response!

Sorry if I was not entirely clear, but we do not have an nRF91, only a custom nRF52840 board with an external LTE modem. We would like to send data to a remote LESHAN server.

[Martin Lesund]

Well, then connecting to the nrf9160 via some serial communication protocol and then forward the data to a leshan server should be possible.
You could use the Lwm2m client sample as reference.

[newUser]

But we do not have an nRF9160.

The LwM2M example you linked is the reason for this post. I want to be able to use that example code, so I need the incorporate a driver for our Quectel BG96 into the zephyr stack. Thus I'm asking if I should create an offloading driver, and how to do that. I know it is possible because the nRF9160 does it, but I couldn't find the source code.

[Martin Lesund]

Here is the source code

[newUser]

Thank your for your reply Martin, but I meant the Socket Offloading code used in the nRF9160. 

I would implement our modem the same way.

[Martin Lesund]

The Serial LTE modem source code is here.
no lwm2m support yet though.