I’ve configured my joystick with “Center stick is zero throttle” and “Allow negative thrust” enabled, yet when I launch QGroundControl or I plug my joystick in the throttle is shown all the way to the left whereas everything else is centered correctly. In that state everything works normally except negative throttle which doesn’t do anything.
The mere act of going to the “Advanced” tab fixes the issue(without touching any options in that tab), the throttle is shown centered as expected and negative throttle works.
Interestingly disconnecting and reconnecting the drone doesn’t cause the issue.
This issue occurs on the latest release of QGroundControl and on v3.5, and on the ArduPilot Rover firmware v4.0 and v3.5 on a PixHawk 2.1. The controller is an Arduino Leonardo communicating via the Arduino Joystick Library.
I am using the latest daily build of QGroundControl with ardurover 4.0. (There is better ardurover support I feel). I have this installed on Linux Mint 19.3.
Flight Controller Omnibus F4 V3 Pro.
I am using joystick control option on QGoundControl via telemetry input of flight controller.
I do not use a radio control transmitter.
I have a similar experience to you.
First I assume your joystick is correctly calibrated. This only needs to be done once.
To fix the negative thrust issue when starting up QGroundControl,
Wait until the flight controller has made a MAVLink connection to QGroundControl.
Select [Vehicle Setup]
Select [Joystick]
Select [Advanced]
Untick box [Allow negative Thrust]
Retick box [Allow negative Thrust]
Return to flight control operation and it should be fine. You need to do this each time you start QGroundControl.
The developers might need to investigate this.
I have seen this on different versions of QGroundControl.
The symptoms are as if on startup, “Allow negative Thrust” has not been selected. Even though there is a tick in the selection box.