MAVLINK Bridge

Serial Connection

Pixhawk TELEM2 is internally connected to the Jetson module. Let us first check the connection on the Jetson terminal. Consider having a MAV connection to companion computers in advance. Check PX4 Docs for the details. For a sanity check, you could run mavlink shell on /dev/ttyTHS0

Ethernet Connection

Since there is no DHCP server active in this configuration, the IPs have to be set manually: Once the Ethernet cables are plugged in, the eth0 network interface seems to switch from DOWN to UP.

You can check the status using:

ip address show eth0

You can also try to enable it manually:

sudo ip link set dev eth0 up

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

ip address show eth0

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
    inet 169.254.21.183/16 brd 169.254.255.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::yyyy:yyyy:yyyy:yyyy/64 scope link 
       valid_lft forever preferred_lft forever

This means the Jetson’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:

ifconfig

eth0    Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx at DOWN
        inet addr:0.0.0.0 DRaddr:192.168.0.254 Mask:255.255.255.0

For me, it is DOWN at first.

To set it to UP:

ifup eth0

ifup eth0...OK

Now check the config again:

ifconfig

eth0    Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx at UP
        inet addr:0.0.0.0 DRaddr:192.168.0.254 Mask:255.255.255.0

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

ifconfig eth0 169.254.21.184

And check it:

ifconfig

eth0    Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx at UP
        inet addr:169.254.21.184 DRaddr:169.254.21.1 Mask:255.255.255.0

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 Jetson terminal:

ping 169.254.21.184

PING 169.254.21.184 (169.254.21.184) 56(84) bytes of data.
64 bytes from 169.254.21.184: icmp_seq=1 ttl=64 time=0.188 ms
64 bytes from 169.254.21.184: icmp_seq=2 ttl=64 time=0.131 ms
64 bytes from 169.254.21.184: icmp_seq=3 ttl=64 time=0.190 ms
64 bytes from 169.254.21.184: icmp_seq=4 ttl=64 time=0.112 ms
^C
--- 169.254.21.184 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3077ms
rtt min/avg/max/mdev = 0.112/0.155/0.190/0.034 ms

And from the FC in Nuttx Shell:

ping 169.254.21.183

PING 169.254.21.183 56 bytes of data
56 bytes from 169.254.21.183: icmp_seq=0 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=1 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=2 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=3 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=4 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=5 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=6 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=7 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=8 time=0 ms
56 bytes from 169.254.21.183: icmp_seq=9 time=0 ms
10 packets transmitted, 10 received, 0% packet loss, time 10010 ms

MAVLink/MAVSDK test

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

For an initial test we can do:

mavlink start -o 14540 -t 169.254.21.183

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:

python3 -m pip install mavsdk

wget https://raw.githubusercontent.com/mavlink/MAVSDK-Python/main/examples/tune.py
chmod +x tune.py
./tune.py