Since Dec.29, 2019, ArduPilot official has updated the firmwares of arducopter(multirotor), arduplane(acrobatic) and ardurover(car/boat) to V4.0. However, the sensor integrated of firmware V4.0 has been modified, making that of some RadioLink PIXHAWK doesn’t function normally as the progress bar doesn’t move when calibrating the compass. If this problem encountered, please follow below steps:

Note The progress bar should be moving when calibrating compass, meaning PIXHAWK functions and is compatible with firmware V4.0. Then there’s no need to follow below steps

1. 1. Connect the PIXHAWK to a GPS module with compass 

Because it is the internal sensor driver modified with the V4.0 firmware and the external sensor remains. To work with an external one, it can function normally.

2. 2. Use the firmware of V3.X instead of V4.0  

Arducopter 3.6.12 https://firmware.ardupilot.org/Copter/stable-3.6.12/fmuv2/arducopter.apj

Arduplane 3.9.11 https://firmware.ardupilot.org/Plane/stable-3.9.11/fmuv2/arduplane.apj

Ardurover 3.5.2 https://firmware.ardupilot.org/Rover/stable-3.5.2/fmuv2/ardurover.apj

Click the links above to download the corresponding firmwares, then load them in the Mission Planner