Can't change takeoff altitude using set_takeoff_altitude()

[aydal]

Hey guys, I tried to change the altitude in takeoff_and_land.py through the following code but ran into an error. Looks like a bug. Would be grateful for insights and help on this!

#!/usr/bin/env python3

import asyncio
import time

from mavsdk import start_mavlink
from mavsdk import connect as mavsdk_connect

start_mavlink()
drone = mavsdk_connect(host="127.0.0.1")


async def run():

    print("Waiting for drone...")
    async for state in drone.core.connection_state():
        if state.is_connected:
            print(f"Drone discovered with UUID: {state.uuid}")
            break

    print("-- Arming")
    await drone.action.arm()

    print("-- Taking off")
    await drone.action.set_takeoff_altitude(100)
    print (await drone.action.get_takeoff_altitude())
    await drone.action.takeoff()
    await asyncio.sleep(30)
    
    print("-- Landing")
    await drone.action.land()



loop = asyncio.get_event_loop()
loop.run_until_complete(run())

Terminal output:

python3 takeoff_and_land.py
Waiting for drone...
Drone discovered with UUID: 5283920058631409231
-- Arming
-- Taking off
Traceback (most recent call last):
 File "takeoff_and_land.py", line 36, in <module>
   loop.run_until_complete(run())
 File "/usr/lib/python3.6/asyncio/base_events.py", line 484, in run_until_complete
   return future.result()
 File "takeoff_and_land.py", line 25, in run
   await drone.action.set_takeoff_altitude(100)
 File "/usr/local/lib/python3.6/dist-packages/mavsdk/plugins/action.py", line 331, in set_takeoff_altitude
   raise ActionError(result, "set_takeoff_altitude()", altitude)
mavsdk.plugins.action.ActionError: UNKNOWN: ''; origin: set_takeoff_altitude(); params: (100,)

[JonasVautherin]

Sorry for the delay @aydal, I've been a bit overwhelmed.

I'm thinking that you may actually contribute to that issue, as now you are familiar with gRPC from the PositionNED PR :-).

If you look at SetTakeoffAltitude:

    grpc::Status SetTakeoffAltitude(
        grpc::ServerContext* /* context */,
        const rpc::action::SetTakeoffAltitudeRequest* request,
        rpc::action::SetTakeoffAltitudeResponse* /* response */) override
    {
        if (request != nullptr) {
            const auto requested_altitude = request->altitude();
            _action.set_takeoff_altitude(requested_altitude);
        }

        return grpc::Status::OK;
}

You can see that response is ignored. Which is wrong: we need to respond with an ActionResult, as defined by the proto file.

SetMaximumSpeed, in the same file, does it the right way:

    grpc::Status SetMaximumSpeed(
        grpc::ServerContext* /* context */,
        const rpc::action::SetMaximumSpeedRequest* request,
        rpc::action::SetMaximumSpeedResponse* response) override
    {
        if (request != nullptr) {
            const auto requested_speed = request->speed();
            mavsdk::Action::Result action_result = _action.set_max_speed(requested_speed);

            if (response != nullptr) {
                auto* rpc_action_result = new rpc::action::ActionResult();
                rpc_action_result->set_result(
                    static_cast<rpc::action::ActionResult::Result>(action_result));
                rpc_action_result->set_result_str(mavsdk::Action::result_str(action_result));
                response->set_allocated_action_result(rpc_action_result);
            }
        }

        return grpc::Status::OK;
}

i.e. SetMaximumSpeed does put the ActionResult into the response.

Would you mind fixing SetTakeoffAltitude such that it behaves correctly? That would be awesome :sunglasses:.

[aydal]

Hello Jonas, Apologies for the late reply. Have built and checked the changes. Changes visible on PR

[JonasVautherin]

Which PR?

[JonasVautherin]

@aydal: Any news on that? I remember you worked on that but I lost track eventually :confused:.

[ghost]

I had the same issues but I used some other work around by setting the takeoff height parameter, MIS_TAKEOFF_ALT

await drone.param.set_float_param("MIS_TAKEOFF_ALT", 20.0)

20.0 metres was the height in my case. That should suffice for now.

[JonasVautherin]

That works, of course, but the fix suggested above would be cleaner. It should not be difficult to fix, and I believe @aydal had it but just did not open a PR with it :confused:.

[ghost]

Alright then, let me give it a shot.

[JonasVautherin]

@vizzbee: sure, it would be awesome!

I don't remember that PR or why it did not get merged. The easiest would probably be to open a PR specific to that bugfix, so that it is easier to merge it. If you do it along with a new feature, it will take more time to get merged :slightly_smiling_face:.

[siddux]

Hi, has the bug been resolved? I tried to modify the takeoff altitude on takeoff example file and still get an error.

[julianoes]

@siddux let me check. I see the last status here: https://github.com/mavlink/MAVSDK/pull/958

[julianoes]

I have updated the pull request. I hope that we can merge it soon now.

[julianoes]

The PR has been merged, this should be fixed in the next release.

[cryptik]

This issue is marked as closed, but it seems to still be an issue. I ran similar code as shown above, calling the set_takeoff_altitude() command as follows:

await drone.action.set_takeoff_altitude(5.0)

The code throws and invalid parameter exception but still sets the altitude value. I can confirm this by calling the get method and verify that it was in fact changed. I am running version 0.12.0 of mavsdk on a raspberry pi.

[julianoes]

I am running version 0.12.0 of mavsdk on a raspberry pi.

@cryptik Can you try the latest version 1.4.0?

[cryptik]

Sorry... I gave you the version I am running on locally on MacOS. I deploy remotely to RPi.. will check the version when I am back at the drone. Another question... for the Mac, it appears the latest version is 0.12.0? I have an M1... is that the latest version?

[julianoes]

M1 is tricky as we don't have mavsdk_server built in CI for it yet. See https://github.com/mavlink/MAVSDK-Python/issues/319.

You can get try to get the latest with python -m pip --upgrade install mavsdk

[cryptik]

Thanks, but worries.. there are other issues I have with the M1 and related libraries... so the remote build on RPi works fine. Will check the version and report back.

When I do the upgrade on the M1, it tells me the requirement is already met... for version 0.12.0. Seems consistent with what is discussed in #319.

[cryptik]

Ok, I checked... on the RPi, I am using mavsdk 1.4.0 which I assumed had this problem corrected... but maybe not for the Pi. I currently catch the exception and then call the get function to confirm that it was actually changed.

[julianoes]

That's odd. It definitely should have been fixed in 1.4.0. I will try to reproduce this.