Hello all,
I am currently working on a custom aircraft equipped with a Here4 GPS puck, Cubepilot CubeBlue, and custom PX4 firmware. I am encountering an issue where the firmware triggers a failsafe due to the following message: “[Warning]: Invalid Setpoints.”
After conducting a root cause analysis, I observed that at a specific timestamp (tested on multiple Here4 units and CubeBlue boards using both standard and custom PX4 firmware versions >1.15.0), the GPS reports low speed accuracy with large error values ranging between 2.5 and 26 m/s. This occurs consistently at fixed timestamps—for example, ~263 seconds in one case and ~255 seconds in another. Further investigation revealed that the error originates from the GPS puck itself via the CAN protocol and is not influenced by any post-processing steps in the PX4 firmware. This issue is consistently reproducible during every flight, including the moment when the failsafe is triggered.
Key observations:
- The Here4 GPS is connected via the blue CAN cable to the CAN2 port on a KORE carrier board.
- The error occurs only once per flight and is consistent regardless of whether the aircraft is armed or not.
- Both fix and fix2 corrections are present throughout the flight.
- When the covariance matrix is analyzed during the accuracy drop, the diagonal elements are unusually high (0.6 to 3), with all diagonal elements showing identical values.
- Using the Here3 GPS with the same hardware/firmware setup does not produce the high variance values observed with the Here4 GPS.
Based on this information, could you please assist in resolving this issue or provide guidance on the next steps?