During PID tuning, have you ever seen a graph like this?


First, attach the log

my situation

  1. Even with PID tuning, toilet pool is not resolved.

  2. GPS replacement, Compass calibration several times, esc calibration, etc. does not solve the problem

  3. If it is not resolved, look at the binary log

  4. Check that Rll, Des Rll / Pit and Des Pit are not very good

  5. Looking at the graphs of Yaw and Des Yaw, I see something strange.

What’s the des yaw graph in that white square?

I’ve never seen a graph like this

Could this be causing a toilet pool?

  1. No problem in no payload flight

  2. There is no such thing in the graph even with 3kg payload

  3. After additionally equipped with 5kg payload, something like that occurred on the graph along with the toilet pool in flight

To solve that graph, what parameters should I touch?

Mag 1 is responsive to throttle, Mag 2 is not. Causing Ground Mag Anomalies and Yaw re-alignment. I suppose this is the cause of the spike in Desired Yaw. Try re-prioritizing the compass’s.

Thank you for answer.
I have been pointed out many times about compass.

I remember this too, but I’m not sure how to fix it.
Could you please take a look if you upload parameters?

FC and GPS are Holybro Pixhawk4 sets


I did look at the parameter file. You have these 2 compass’s:

Both on the I2C bus so external.

You have this priority:

#1 is causing trouble #2 is not.

Post a screen shot the HW ID screen from Mission Planner to confirm.

Whoops… I guess I’ve already uploaded a parameter once.


Are you saying you can just change it like this?


Show me the compass page in the mandatory hardware Page.

No, change the compass priority on the Mandatory Hardware>Compass screen. Or just disable the problem one.

I have disabled #1 because compass#1 caused an abnormality.

After Hexa boots, the EKF in the Hud window turns red, and this has not been resolved after waiting for more than 10 minutes.

HWID 658953 is you external compass as of current configuration its second priority .make it priority one by clicking the UP arrow and reboot the flight controller.

And check for external compass appear on top of the table If so then redo the compass calibration outside after gps lock …then you good to go.

OK, the compass on I2C bus 0 is the Internal one on Pixhawk 4’s. Disable that. The screen shot shows it still active.If you just re-prioritize and the internal one is still active you can still have problems.

Hasn’t this all been covered before?

kalai1219 says to change only Priority, please check it once

  1. Change Priority as kalai1219 said

  2. Dave, as you said, disable the internal compass (now #2)

  3. Reboot

  4. Compass Calibration

is this correct?


I would disable the internal compass. Sure, re-calibrate after doing so if you like but it’s not nessesary.

Even if I eventually disable the internal compass, should I change the Priority?

Additionally, after all, this isn’t a Pid issue, it’s all a GPS issue…

It’s a lot harder than i think


  1. Compass Priority changed, #1 and #2 changed.

  2. Disabled compass2 as you said.
    (I swapped #1 and #2. Now #2 is the old internal compass.)

Hud’s EKF does not change from red

GPS is also 3d dgps

Show gps hdop is below 1? And check message tap that EKF2 using GPS.

Hdop is 0.9

EKF2 Locking is cleared

but GPS status is 3d dgps not 3d fix

thank you

3D DGPS is better than 3D Fix, as you received corrected data from GPS system.

long time no see.

I’m back to report.

  1. Changed Compass Priority.
    (Internal:#1 -> Internal:#2)

  2. Disable the internal compass

  3. Reboot after performing compass calibration.

  4. Fly

Result: The toilet pool phenomenon disappeared.

But is it safe to fly with only one external compass?

In fact, during the flight, Hexa flew by tilting her head slightly to the side rather than flying in a straight line.

Among Rtl, it deviated significantly once at all.

Binary log

I’m sorry to have been troublesome

Please take a look at the log and let me know if there is anything I need to correct.

I’ve heard many stories that 3d dgps is better than 3d fix.

However, when in 3d dgps, the drone feels wobbly rather than powerful.
Continues to flow while hovering