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Ethernet Connection

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Link-local networking setup between CM4 and FC

Local cable

To set up a local ethernet connection between CM4 and the flight computer, the two ethernet ports need to be connected using a 8 pin to 4 pin connector.

The pinout of the cable is:

8 pin: 1 A 2 B 3 C 4 D 5 (not connected) 6 (not connected) 7 (not connected) 8 (not connected)

to 4 pin: 1 B 2 A 3 D 4 C

IP setup on CM4

Since there is no DHCP server active in this configuration, the IPs have to be set manually: First, connect to the CM4 via ssh by connecting to the CM4’s wifi (or use a Wifi dongle). Once the ethernet cables are plugged in, the eth0 network interface seems to switch from DOWN to UP.

You can check the status using:

You can also try to enable it manually:

It then seems to automatically set a link-local address, for me it looks like this:

This means the CM4’s ethernet IP is 169.254.21.183.

IP setup on FC

Now connect to the NuttX shell (using a console, or the MAVLink shell), and check the status of the link:

For me it is DOWN at first.

To set it to UP:

Now check the config again:

However, it doesn’t have an IP yet. I’m going to set one similar to the one of CM4:

And check it:

Now the devices should be able to ping each other.

Note that this configuration is ephemeral and will be lost after a reboot, so we’ll need to find a way to configure it statically.

Ping test

First from the CM4:

And from the FC in Nuttx Shell:

MAVLink/MAVSDK test

For this, we need to set the mavlink instance to send traffic to the CM4’s IP:

For an initial test we can do:

This will send MAVLink traffic on UDP to port 14540 (the MAVSDK/MAVROS port) to that IP which means MAVSDK can just listen to any UDP arriving at that default port.

To run a MAVSDK example, install mavsdk via pip, and try out an example from MAVSDK-Python/examples.

For instance:

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