Set Guided mode with MAVSDK-java

[TeoVal138]

Hello everyone,
I'm developing an android mobile app with mavsdk-java to control my ardupilot drone, in this days I've been trying to set the guided mode in order to takeoff autonomously.
Can you please tell me what can I do?

Many thanks in advance

[JonasVautherin]

I think that the equivalent to "guided" in PX4 is "offboard". Did you try the offboard plugin? Not sure if it works with Ardupilot though 🤔. Worth trying with a simulator! 😊

[TeoVal138]

Hi Jonas,
Thank you for the support 😊
I was trying with a simulator to use offboard but the "system.getOffboard().start()" method doesn't respond and "system.getOffboard().isActive()" is always set to false so I think it's off limits unfortunately.
For a while I tried with the Shell plugin but I didn't find anything useful in the online forums, do you happen to know if I could actually use it to change the flight modes and if so what command should I use?

[JonasVautherin]

Calling offboard.start() should just change the flight mode, see here:

_system_impl->set_flight_mode(FlightMode::Offboard)

which ends up translating that to an Ardupilot flight mode here:

make_command_ardupilot_mode(flight_mode, component_id);

which e.g. for a copter will translate to Guided here:

        case FlightMode::Offboard:
            return ardupilot::CopterMode::Guided;

So I think it should work.

The problem is that at least the last part is not available in MAVSDK v1.4.16 (latest release, see here), only on the main branch.

I see two three solutions for you (none of them ideal, unfortunately):

1. You build MAVSDK from source (from the C++ core up to MAVSDK-Java)
2. You wait until MAVSDK v2 is out, but that may take time. It is being tracked here.
3. You fix v1.4.16 and open a PR, such that we can release v1.4.17 with the changes you need. You can get inspiration from the main branch (where I believe it should work), but honestly I don't know how easy that will be. Could be quite straightforward, I think.

[TeoVal138]

Thank you Jonas I will try to follow your advice! 😊
So no other mavsdk-java plugin would allow me to switch modes right?
I'm not just talking about the guided mode set but also about the other modes set

[JonasVautherin]

The MAVSDK plugins set the mode as required. For instance the mission plugin will set the mission mode, the action plugin will set the RTL, takeoff, land mode, etc.