[SOLVED] RC2 wrong PWM

Hello everybody
I’m building a coaxial frame drone with Navio2 and Raspberry Pi2 and I have a problem with the RC channel n.2: the PWM output seems to be “wrong”, it that it causes the servo to make a lot of noise and vibrations. On one servo, I also see the “magic smoke”!
Searching the forum, I didn’t see any known issue about that… so my question actually is: which kind of servo do you suggest to use with Navio2? analog or digital? there is a servo model that is tested and certified for use with navio2?


Hello Ambrogio,

This is most likely due to 400Hz PWM frequency, try changing RC_SPEED parameter to a lower value. Something like 100Hz should work.

Where to find that parameter? In the full parameter list I cannot find a parameter named “RC-SPEED”??

Hmm… maybe it is not implemented for single copter. @george.staroselskiy can you please have a look?

Instead of Ambrogio I’m using APMrover2 and there I cannot find the parameter RC_SPEED. Perhaps you can check this too.

APMRover has 50Hz servo rate, so this is not related to your case.

Hi ivereninov
Actually I am not able to find the RC_SPEED parameter…
My plan is to connect an oscilloscope and check whether the PWM signal is correct or not. What sounds strange to me is that RC1 works perfectly…

Thanks for your time!

A scope will be perfect, you can also use our examples (servo) from GitHub to check if everything is good with the hardware.

I connected an oscilloscope to RC1 and RC2 output and I see something strange: frequency is 4 ms (see attached screenshot, time is 2 ms/ div). Is this correct? shouldn’t it be 20 ms?

Any help is appreciated!

Hello everybody

I finally found the parameter that controls PWM frequency
The parameter name is MOT_SV_SPEED.
The original value was 250 hz. I changed to 50 (hz) and now I see the correct WPM output