Dual motor controller setup issues

Moved backwards in our development to change out some failing technology and try to get the correct trims for right-hand only (Mode 2 transciever, center loaded stick) reversing behaivior I was expecting. Our previous working prototype had a forward only setup using left stick throttle in manual. As a skid steering UGV, it wasn’t too essential to our tuning process at the time. But we’re also using it for real farm tasks and the reverse behaivor would be helpful.

I’ve got two new competing issues:

  1. Right wheels are moving forward after safety switch disengaged and MOT_SAFE_DISARM=1 but before ARMING, which is concerning from a safety perspective. Crappy SD card (part of the aformentioned equipement fail) means I don’t have any of our logs for this time, but I’ll generate some today with LOG_DISARMED set.

  2. Forward and reverse behaivior on wheels as expected but right wheels are turning at a much slower rate. Signal interference? I wish I had my oscilloscope. Observation of right MC leds indicates that is isn’t recieving a HIGH directional signal from the AUX 6 pin.

I’ll reply later today to this topic with params and logs if anyone can help.


This looks like the range the ESCs are accepting doesn’t match the range output by the Flight controller’s PWM output pins.

In particular if the right wheel is moving then it’s likely that the SERVO3_TRIM isn’t quite right for the ESC. I think the MP’s motor test screen is a good way to try and get this sorted out because it will allow trying different throttle percentages to each wheel so their speeds can be compared. Make sure they start spinning at about the same throttle percentage… Adjusting the SERVOx_TRIM up or down to make them the same. Ideally the motors should start spinning very slowly when the throttle percentage is set to 1%. If you find the throttle percentage must be higher (like 5%) then the MOT_THR_MIN parameter should be adjusted. It’s often not possible to get it absolutely perfect.

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Adjusting Trim and Min servo values to 100 and 0 fixed the problem on the Cytron MD30C controllers using the brushed with relay setup and the throttle on the center locked transmitter control stick. The second issue was a short in the toggle switches that serve as Safety Interlocks for motors, still wish I had my oscilloscope though.