Toilet bowl effect in loiter mode –quad running ChibiOS board

My 250 size quad is running Open Pilot Revolution board (non Pixhawk board) using ChibiOS operating system. When switched to loiter mode, the quad experiences toilet bowl effect. I use default setting (param attached) after flashing the firmware. The built-in compass in the Revolution board works fine as witnessed by the correct display of direction on the HUD of MP corresponding to the direction of the board, Pls see attached photo on the layout of the quad.

I have another quad 450 size,. FC is Pixhawk running arducopter V3.6.1. This quad works satisfactorily in loiter mode, and it uses mostly default settings.

Both Revolution and CC3D belong to the project Open Pilot family, and this link for CC3D :– says
NMEA is no longer supported , and the page refers to set up of UBX protocol (3rd paragraph).

GPS connected to Pixhawk normally uses NMEA as protocol. Now that the board is ChibiOS board, could it be the toilet bowl effect due to malfunction of the mini ublxo NEO-6M GPS because it is pre-configured to UBX instead of NMEA ?

Can anyone help to trouble shoot the problem with the attached param of the quad 250 ? DF log is not available because there is no memory card on Revolution board.
Quad250.param (13.7 KB)

Thank you.

A 250 size quadcopter will not be expected to fly well on default settings. Start here with basic tuning setting for your craft:

Can you not use block logging on that board? It works on other boards w/o an Sd card.

Edit: You can log to dataflash on that board. From the Hwdef file:
enable logging to dataflash

Good day, just perform a soft autotune of your copter and just adjust also the INS_GYRO_FILTER to 40 or 80 and INS_ACCEL_FILTER to 40.

Hi Dave,

Thank you for yr reply. Will follow the basic tuning as you suggested.

The 250 size quad performs very well in Stabilize mode. Reading all related threads in forum, towel bowl effect seems relates to compass setting. My 450 size quad holds very well in LOITER mode with default setting. Does the difference in size between 250 and 450 quad make the difference in LOITER mode ?

What is block logging ? How do I do it ?

Also how do you do soft autotune , versus autotune out at a field ?

Thank you for your help.


Set LOG_BACKEND_TYPE to 4 and then a Log Bitmask to enable some data. Toilet bowl could be a compass problem or it could just be general stability. High vibrations possibly.

I don’t know what “soft” AutoTune is. Make the tuning changes and perform a hover in AltHold for a minute or so and post the log assuming one is saved.

If you want provide the autotune just set is as weak with this parameter 0.050, if you want change just set this parameter for the autotune you want: 0.1=agressive, 0.075=medium.
Just add gel pads for isolate your fc by high vibrations on all axis…

Thanks, Dave.

In my version of arducopter V3.6.5, the param LOG_BACKEND_TYPE has only 3 options, 0, 1, 2 and 3.

No option 4. What is yr arducopter version ?

Will figure out this before making autotune changes.

3.6.5 is over a year old. Update to current stable, V4.0.3, and also update Mission Planner to latest Beta.

Hi Dave,

I set the LOG_BACKEND_TYPE to 3 and enable some data in LOG_BITMASK using default, I got “Bad logging” error message which prevents me from arming the motors.

When I disable both by setting back to 0, the error message disappears and I can arm the motors.

That’s because 3 is not Block logging. Set it to 4. If you don’t see this option set it to 4 anyway. This assumes you have updated to current stable.

Hi Dave,

Thank you for yr support. I updated both the MP and arducopter to the latest version. And also set the LOG_BACKEND_TYPE to 4, and enable LOG_BITMASK by using default value 830. See attached.

But how do I access the Block logging ? The MP only provides access to download the dataflash log via Mavlink. But I have no dataflash card in FC.

Hi Frankie,
I had assumed it should work because it does on other boards with only flash memory. It does on my Omni F4 Nano V6 for example. There are so few people using that board perhaps you are the 1st one to test this feature. Can you post your parameter file from V4.0.3 anyway, maybe there is something so see.

Hi Dave,

Pls see attached the parameter file, as you requested.

My question is : how do I access the Block log file , now that I set the LOG_BACKEND_TYPE to 4 and also enable some data for the LOG_BITMASK ? Which button/icon I should click to acces the log file ?

The only thing I did so far is to donwload the Dataflash log from the tab underneath the HUD display in MP. Do you mean this is the place to get the log file if it works ?

Thank you for yr help.


Param__Arducopter V4.0.3__Revo board.param (17.1 KB)

Yes, the same place you would normally download logs from. I’m not sure why this doesn’t work with your Revo board. I don’t see anything in your parameter file to prevent it either. The Hwdef file seems to suggest it can support logging but perhaps not.

Back to tuning it doesn’t look like you have updated the basic tuning parameters for a 250 size craft as per the link above. I would do that and then try an Autotune.

Hi Dave,
You edit your earlier message :–
Edit: You can log to dataflash on that board. From the Hwdef file: enable logging to dataflash define HAL_LOGGING_DATAFLASH

I have no background in coding or software. How and where do you do this ? What is Hwdef file ?
Will update the basic tuning param and do autotune in weekend, weather permitting.
Thank you for yr continued support.

You don’t need to code anything, it’s already done. The Hwdef file (Hardware Definition) allows Ardupilot to access each boards hardware configuration. They are here for reference: