nrf9160dk + W5500 Ethernet Shield + modbus_tcp_server example socket creation returns 23 error

[makoto.inoue]

Hi,

I'm evaluating a scenario of using an nrf9160 with an HMI, communicating via modbus tcp connection.

The hardware setup looks like this:

HMI <-----> Ethernet switch <-----> nrf9160dk + W5500 Ethernet Shield

With this layout, I've managed to get the dhcpv4_client example to function properly (I get a valid ip), so I think my W5500 overlay file is okay.

The problem is that when I load the modbus_tcp_server example I get an error during socket creation with an error code 23.

The same code with nrf5340dk + W5500 Ethernet Shield does not have this error, and it is able to receive and send modbus tcp messages.

My guess is that the I'm not configuring something properly in Kconfig. From what I read, the error code 23 is "too many open files in system" - this could be because nrf9160dk + W5500 Ethernet Shield setup has two ipv4 interface instead of one, but I am not certain. I am using static ip for the modbus_tcp_server example.

I'm attaching my prj.conf and Kconfig fragments files.

Appreciate your help in advance!

Best Regards,

Makoto5875.prj.confnrf9160dk_nrf9160_cpuapp_ns.conf4370.nrf5340dk_nrf5340_cpuapp_ns.conf

[Øyvind]

Hello, 

I'm not familiar with the modbus_tcp_server sample, as this is part of the Zephyr repository. What version of the nRF Connect SDK are you working on?

The same code with nrf5340dk + W5500 Ethernet Shield does not have this error, and it is able to receive and send modbus tcp messages.

Sounds like an issue with e.g. too many sockets open. There is a known issue that Zephyr does support multiple network interfaces. Have a look at this ticket:  nRF9160 Ethernet and LTE both available but cannot open sockets under Ethernet 

Kind regards,
Øyvind

[makoto.inoue]

Hi, Øyvind,

Thank you for your reply. I did not know Zephyr does not support multiple network interfaces. Good to know.

Since I do need ethernet connection to HMI and I want Cellular connection then would something like below setup work?

HMI <----> Ethernet switch <-----> nrf5340dk + W5500 Ethernet Shield <-----> nrf9160dk (with AT Client or LTE Sensor Gateway or similar)

If it does, would FOTA be possible for the nrf5340? If FOTA is possible, are there examples?

Best Regards,

Makoto

[Øyvind]

Hello Makoto, 

makoto.inoue said:

Since I do need ethernet connection to HMI and I want Cellular connection then would something like below setup work?

Yes, this seems plausible for the use-case you are looking for.

makoto.inoue said:

If it does, would FOTA be possible for the nrf5340? If FOTA is possible, are there examples?

Do you mean downloading image via nRF9160 and updating the nRF5340? If so, yes, there is a sample, Cellular: LwM2M Client, what you can evaluate. This uses UART to update an external MCU.

Kind regards,
Øyvind

[makoto.inoue]

Hi Øyvind,

Thank you for the reply. Good to know that layout will work and FOTA example is available. I will check it out.

Best Regards,

Makoto