Is it possible to define a 4th MAVLink instance in PX4?

[Aman]

Hello everyone,

I’m currently working on a project where I need to connect four devices to the Pixhawk (Cube Orange+) via MAVLink. According to the PX4 documentation, there are only three MAVLink instances defined by default: MAV_0, MAV_1 and MAV_2.

My question is:
Is it possible to define and use a 4th MAVLink instance PX4?

If yes

What’s the proper method to configure it?
Are there any system limitations or best practices to follow when running more than three MAVLink connections?

Any guidance or examples would be greatly appreciated!

Thanks in advance.

[JulianOes]

I think 4 should work fine. It’s just not set up.

It will need a few tweaks to enable it:

• For a start: PX4-Autopilot/src/modules/mavlink/module.yaml at 9a0b666debcff4292ce51c4a52aab1f2e346e8e0 · PX4/PX4-Autopilot · GitHub
• Then, add defaults for all params: e.g. PX4-Autopilot/src/modules/mavlink/module.yaml at 9a0b666debcff4292ce51c4a52aab1f2e346e8e0 · PX4/PX4-Autopilot · GitHub
• And I think it should not trigger here because the define is 6: PX4-Autopilot/src/modules/mavlink/mavlink_main.cpp at 9a0b666debcff4292ce51c4a52aab1f2e346e8e0 · PX4/PX4-Autopilot · GitHub

[ryanjAA]

@hamishwillee this should be in the docs or advanced or something. I’ve struggled with this before a long time back and had to figure this out.

[JulianOes]

We should just add it in code.

[Aman]

Thank you @JulianOes…,
I will go through this

[ryanjAA]

Ya, I don’t know the downside. I wondered if it was a limit or consumed too much cpu on f4 processors a long while back but insignificant now…