Control nRF9160 with a MCU using zephyr

[samuel4]

Hi

If we're using an external MCU to control a nRF9160, is there any software support in zephyr available? The nRF9160 is well supported by zephyr if I program the cortex-M33 application processor. Are there some device tree options to integrate an external nRF9160 in zephyr? I don't want to write AT-commands from hand, but the nRF9160 has too less SRAM for my application.

Best regards
Samuel

[Hakon]

Hello,

If we're using an external MCU to control a nRF9160, is there any software support in zephyr available?

Have you considered using the serial LTE modem sample in the SDK?

[samuel4]

Hi

Yes I did. But do you have zephyr support for the other device then? Let's say I connect a nRF9160 with a nRF5340 over UART. The serial LTE modem sample runs on the nRF9160. Is it possible use zephyr sockets on the nRF5340 with some device tree settings? I guess, I need have to write a device driver like this: github.com/.../quectel-bg9x.c

[Hakon]

samuel4 said:

Yes I did. But do you have zephyr support for the other device then?

Zephyr is supported on nrf5340.

samuel4 said:

Is it possible use zephyr sockets on the nRF5340 with some device tree settings?

Do you mean the Zephyr native network stack?

[samuel4]

Let me recapitulate. Let's say we have a hardware consisting of a nRF9160 and nRF5340. They are connected via an UART. Now I want to use the zephyr socket API on the nRF5340 to send data over the cellular network. That means, zephyr (on the nRF5340) needs to know that there is an nRF9160 on some UART interface and how socket commands are translated into AT commands. In the zephyr documentation I found two device tree binding for external cellular modems. I have posted a link above to the socket wrapper of one of them. But I haven't found a device binding for an external nRF9160.

So the question is: If I have such an hardware architecture, can I use the zephyr socket API on the nRF5340 to send data over a cellular network? Which means that there must be some specified software running on the nrf9160 receiving AT commands and more important: There must be a way to tell zephyr on the nrf5340 that there is a nRF9160 connected to it. Otherwise we probably need to implement our own device tree binding.

Why I am asking that? The nRF9160 as cellular modem is great, but it is not scalable. It is limited to 1 MB flash and usable 192 KB SRAM. So if we develop an application that needs more ROM/RAM, we could just take the same zephyr application on a second MCU and connect the cellular modem over a device tree binding. At least for socket commands it should be portable that way.

[Hakon]

samuel4 said:

The nRF9160 as cellular modem is great, but it is not scalable. It is limited to 1 MB flash and usable 192 KB SRAM.

Why do you need so much RAM in your application? Is it not possible to run the IP stack on the nrf9160 with the modem_lib?

I believe it should be possible to run the IP stack on the nrf5340 and use CONFIG_NET_SOCKETS_OFFLOAD.