(Rare?) pre-arm failure: GPS 1 failing configuration checks


While setting up my first Arduplane aircraft, I am encountering the following pre-arm failure:

Pre-arm Message:
PreArm: GPS 1 failing configuration checks

Followed by:
GPS 1: u-blox posllh rate configuration 0x3FE

All messages are these:
GPS 0: detected as u-blox at 115200 baud
GPS 1: u-blox posllh rate configuration 0x3FE
PreArm: GPS 1 failing configuration checks
PreArm: Compasses inconsistent
EKF2 IMU1 is using GPS
EKF2 IMU0 is using GPS
EKF2 IMU1 Origin Set
EKF2 IMU0 Origin Set
EKF2 IMU1 tilt alignment complete
EKF2 IMU0 tilt alignment complete
GPS alt: 38465
EKF2 IMU1 initial yaw alignment complete
EKF2 IMU0 initial yaw alignment complete
EK2: Changed EK2_GPS_TYPE to 1
GPS 0: detected as u-blox at 115200 baud
Airspeed sensor calibrated
Ready to fly
Airspeed calibration started
Barometer calibration complete
PX4v2 0043002C 30365115 31313731
PX4: c4dfb9bf NuttX: 258f2257
ArduPlane V3.7.1 (22b5c415)
Initialising APM
Calibrating barometer

The GPS seems to work. What might be the cause of this error and what would the next step to fix it? From checking Arduplane’s code it seems to be failing to configure the NAV POSLLH messages properly. But why only these and not the others?

Thanks for your help!


Following, I have this sometimes with only gps connected.
Gps 0 = primary gps
Gps 1 = secondary gps
Rebooting pixhawk solve the problem for me but why sometimes we got this error ?

It’s actually failing to configure almost everything, we simply print out the first configuration item that is failing. The 0x3FE tells me that the following messages are all failing to be configured as well : posllh rate, status rate, solution rate, velned rate, dop rate, hw monitor rate, hw2 monitor rate, raw rate, version. If you notice as well part way though the boot process the EKF gave up on trying to use the GPS as a 3D GPS. This occurs if the GPS isn’t providing us with a vertical velocity. Given that u-blox always provides this we can tell that it isn’t being correctly configured.

The most common reason for this to fail is actually bad wiring or an intermittent connection (usually on the Tx line to the GPS). Because the GPS is being detected reliably we know we are recieving at least some correct data. I’d check the wiring harness first to ensure that this all looks good.

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Thanks for the detailed replies…

I was thinking in the same direction because my cables indeed are not looking trustworthy. If I understand the code correctly, before the posllh-rate is configured, other must have succeeded. So it is a bit strange, that it consistently fails at exactly this point.

Is it possible, that the u-blox could be misconfigured so soundly, that I need to attach it directly to the u-center to correct some basic parameters?

Well i have the same problem with 1FFF as the rate donfiguration, and i was working fine before i made a wrong upload with QGC that erased all my AC parameters , only one m8n ublox.The position reported by the GPS is accurate.Any idea, my cable just not have become defective in few days…