Airspeed Calibration not working on Pixhawk 5X VTOL Firmware

[poyatabrizi]

Issue Details
When performing a calibration, the process just goes through without me having to blow into the pitot
After above-mentioned calibration, the speed with no wind reads at ~9m/s or ~30km/h
I have tested Ardupilot firmware and my standby airspeed reads around ~2m/s.

To Reproduce
-Connect the 45250 airspeed sensor via I2C
-Navigate to sensors and airspeed
-After sensor calibration, reboot
-Check airspeed value on the main screen

Expected behaviour
I expect the calibration will take into account the offset of the sensor and result in close to 0 airspeeds when there are no wind (i.e. indoor)

Log Files and Screenshots
Refer to forum chat where multiple people are experiencing this and there are screenshots provided.
https://discuss.px4.io/t/airspeed-sensor-is-off-by-9m-s-or-30km-h/25901

Drone (please complete the following information):
Pixhawk 5X flight controller
VTOL - Generic Quadplane VTOL
45250 5A1 airspeed sensor
Qground Stable Version 4.0
PX4 Firmware: Standard VTOL (Generic Quadplane) Firmware 1.12.3

Additional context
Add any other context about the problem here.

[gruffymax]

It looks as though the calibration is working as SENS_DPRES_OFF is set to the zero differential pressure value sent from the sensor. In my case the 4525 sensor reports 145 pa at rest and my SENS_DPRES_OFF is also set to 145.
It seems as though this offset value is not being subtracted from the raw differential pressure before being used to calculate the airspeed. Manually changing SENS_DPRES_OFF to any value makes no difference to the airspeed displayed in QGroundControl.

[gruffymax]

Looking through the driver for the MS4525 shows that a differential pressure is subtracted from the raw pressure in drivers/differential_pressure/ms4525/ms4525_airspeed.cpp:215
report.differential_pressure_filtered_pa = _filter.apply(diff_press_pa_raw) - _diff_pres_offset;

Tracing _diff_pres_offset back leads to the function Airspeed::ioctl, lib/drivers/airspeed/airspeed.cpp:114 which sets _diff_pres_offset. This function does not appear to be called anywhere so _diff_pres_offset stays as 0.0f.

[ryanjAA]

Which version of px4 are you running. I’ll give this a try tomorrow.

[poyatabrizi]

Sorry, I forgot to mention the Firmware details. it is now added to my original comment and it is v 1.12.3

[vincentpoont2]

Sorry, I forgot to mention the Firmware details. it is now added to my original comment and it is v 1.12.3

I just reproduced it, it seems like it is only happening with v1.12.3 and not with Master firmware. Can you use try using Dev build (master)? @bkueng @dagar Was there something that was change recently related to this?

1.12.3
https://user-images.githubusercontent.com/46874772/153453307-5b7527b4-2c97-41f3-add6-a69098815077.mp4

Master FMuv5x Firmware
https://user-images.githubusercontent.com/46874772/153453635-55c37c05-9603-45be-9d59-18fa2a458546.mp4

[jhoexp]

Same problem here, Holybro 5x, 4525 airspeed sensor, 1.12.3, vtol standard quadplane airframe: calibration does not complete correctly (the process concludes without letting you blow into the pitot). The result is that aispeed reads large offset from 0, even when there is no wind indoor and the vehicle is standing perfectly still.

[SJ-Jang]

I am currently having the same problem.
Do we have a modified version?

[VTOLDavid]

Same problem here with Cube orange, Px4 1.14 beta and Sensirion sdp33

[junwoo091400]

Tracing _diff_pres_offset back leads to the function Airspeed::ioctl, lib/drivers/airspeed/airspeed.cpp:114 which sets _diff_pres_offset. This function does not appear to be called anywhere so _diff_pres_offset stays as 0.0f.

I have just checked and this is correct. The offset variable isn't getting properly updated in v1.12.3.

However, for v1.14 beta this should have been resolved, as the offset is now decoupled from the airspeed sensor driver, and is taken into account inside airspeed calibration code alone.

PX4-Autopilot/src/modules/sensors/sensors.cpp

Lines 59 to 61 in 18898f1

	#if defined(CONFIG_SENSORS_VEHICLE_AIRSPEED)
	/* Differential pressure offset */
	_parameter_handles.diff_pres_offset_pa = param_find("SENS_DPRES_OFF");

@VTOLDavid Did you indeed experience the problem of Airspeed calibration skipping the step of "blow into the pitot tube" on it's own using v1.14 beta?

[junwoo091400]

Also, this should have been fixed starting on v1.13, from this commit: d1d15a6

For now I don't know if it would be valuable to backport and fix this bug in v1.12 🤷

[junwoo091400]

However, for v1.14 beta this should have been resolved, as the offset is now decoupled from the airspeed sensor driver, and is taken into account inside airspeed calibration code alone.

@VTOLDavid @SPuigUAVW could you check again whether this problem is indeed present in v1.14? It should not be here, but I don't have the setup to confirm that 😢

[DronecodeBot]

This issue has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there:

https://discuss.px4.io/t/px4-maintainers-call-july-11-2023/33057/1

[VTOLDavid]

We installed v1.14 last week. We had different problems with pitot calibration and USB connection:

• USB connection for cube orange does not work in latest QGC 4.2.6. Once flashed in last QGC version it disconnected. Only connected via USB in a older version of QGC 4.2.4.
• With this older version we configured a datalink.
• With QGC 4.2.6 over a telemetry link pressing pitot calibration shows nothing. The second time shows the error Command denied during calibration: 241
• With QGC 4.2.4 over a telemetry link we were able to calibrate the pitot normally.

Sems that the USB driver problem with cubeorange is interfering here, something changed in QGC and we had some random problems...

[junwoo091400]

@ryanjAA provided this log of an Airspeed calibration working fine with the latest release/1.14 branch, using the same SDP33 sensor: https://review.px4.io/plot_app?log=079cea16-699f-47c8-93b6-9639f5d57d00, and as you reported, the problem seems to be in QGC.

Could you create another issue on QGC repo and tag me there? @VTOLDavid

[DronecodeBot]

This issue has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there:

https://discuss.px4.io/t/px4-maintainers-call-july-18-2023/33189/1