sensors/vehicle_air_data: don't publish if there aren't any healthy sensors remaining

[dagar]

Possible fix for #15223.

[dagar]

This has been pulled into #15235 where the same issue was fixed for magnetometers (and verified).

[julianoes]

@dagar this does not actually work. The only output I see is:

[px4         ] ERROR [vehicle_air_data] sensor_baro:#0 failed:  STALE!, reconfiguring priorities

but nothing regarding switching to GPS.

Here is a log: https://logs.px4.io/plot_app?log=6da28929-ce23-48be-8b28-d0b319d07e13

[dagar]

Yes, I debugged and fixed it as part of #15235.

What I discoverd is that the validator group state (overall error) doesn't clear until all the sensors are back to healthy. So instead what I did was only publish the current primary if it's healthy. Thanks for testing it.

https://github.com/PX4/Firmware/blob/42a4f844424ba8269a82ded6680eb92a63b13af1/src/modules/sensors/vehicle_air_data/VehicleAirData.cpp#L192-L194

[julianoes]

@dagar when I tested #15235 it didn't work either. I'll try again.

[julianoes]

@dagar ok I tried again and I can see that it does fall back but there are two issues with it:

1. It takes about 25 seconds until it switches even though it could do much quicker, right?
2. Once you land and do another flight it climbs indefinitely.

[julianoes]

@dagar ok you're right, it works correctly but only if the temperature is also "stuck". I had to fix that with 358799b.