Servo moves rough

Hello, I am currently upgrading a Logo 600 to Pixhawk Mini. On the swashplate I use Futaba BLS451 servos. It is controlled by a Futabe S.Bus receiver.

Now I notice that the servos move roughly. If I connect the servos directly to the receiver, the servos run much smoother.
I have set the parameter servo_rate to 200. 200hz fits for this servo type.

As a test I also tried an align ds610 servo, with the same behavior.

To me it looks like the servo is skipping small steps.

Is this behavior normal for Pix FC or can it be changed?

Thank you for your replys


I connected my second PIX Mini 4 to the Futabe servo today. Again, the servo runs rougher than when I connect it directly to the receiver.

With my few beginner experiences, I have not noticed this so far. Probably also because I have so far only quite coarse running servos connected to my FCs.
Now I have taken for the first time Futaba servos, which run very smoothly. That is why I now notice the rough running.

I am probably looking for a fault that is not a fault at all.

But it would help a lot to calm me down if someone could tell me that this rough servo behavior is normal with the FC.

Please give me a comment on my “problem”.

Thanks a lot


@heri please post a log file. If it is happening while disarmed then you will have to enable logging while disarmed by setting LOG_DISARMED to one.

Hi Bill, I will do so.

Hi Bill,

I have activated the LOG_Disarmed parameter and created a log with it. I link the log file here:!AjSq727ChpJzgQxrcn4eMO9nx76y?e=pVmYU0

In the first few seconds of the log, I set the Servo Mode to “Passthrough” and then later to “Disabled”. This is for your information.

Don’t be surprised about the power supply parameters. The power board is powered by its own battery (2S) and is not hooked up to the drive battery.
The servo rail is supplied with 6V (5A - 15A) from the BEC of the controller.

Would be happy if you could tell me a hint for the rough running behavior of the servos, or give me an all-clear.

Many thanks.


@heri I will look tonight. Maybe you can video this behavior and post a link. Now that I think about it more, I’m not sure I will be able to see the behavior in the data as the servo output is logged at 10hz. I can’t imagine the flight code is causing this so it has to be at the hardware level which I can’t see in the log. The log will give me your Params so I can look at those to see it I can notice anything odd.


here I made a video.!AjSq727ChpJzgQ5kNmqt-8SVKipp?e=ddVV0K

Unfortunately, I have now completely finished my cabling and installation of the FC. At the moment it would be labor intensive to unplug the servos from the FC and plug them directly into the receiver to have a comparison.

I hope you can hear and see that the servos are not running smoothly. It seems like they are skipping intermediate steps.
Everything else is working as it should. I have everything set up and might dare a first test flight with the logo.

I always have a little shaky hands before the first flight.