RC pass through does not work with CH7

I have designed and built a unique helicopter that uses two forward facing tail rotors to provide anti-torque and directional control as well as forward thrust. I have a servo to controlling directional axis and another servo controlling forward thrust which are mechanically mixed for the tailrotors. I have selected servo only for the yaw axis in the set up. I can only get channel 6 to provide an RC pass through. I want to use channel 6 to perform PID tuning. How do I get channel 7 to provide an RC pass through? I used the function parameter to set the RC pass through on channel 7 but that did not seem to work. Looking for how to configure channel 7 for an RC cost through.

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  • Developer

    It may be that we don't support pass through on ch7 for helicopters because it would conflict with the external gyro output (the channel use is mentioned at the bottom of this wiki page).  The pass through should work on higher channels (assuming you're using a Pixhawk).  In Copter-3.3 on a Pixhawk I'm 99% sure it works on higher channels.

    • After doing a little digging in the code.  I found the line of code AP_Motors_Heli::Init that disables being able to use channel 7 for Aux channel functions.  If I'm not using any of the tail types for channel 7, do you think it would be acceptable to allow the aux channel functions.  I was thinking of using an "if" statement to allow the aux functions only for the "servo" option of tail types.  Looking at the code, I didn't see anything that would cause this to be a problem.  Please let me know what you think.



    • Developer

      Maybe we should use the RC_Channel_aux functions (i.e. RC7_FUNCTION. etc) to define which output is used for the heli tail?  That would allow it to be moved around.

      RobL knows best about heli of course so he should comment really.

    • I saw your post on another discussion regarding channel pass through.  I will try the idea of using the camera mount tilt to use a higher output channel.  a slightly lagged response may be acceptable for this forward thrust controller.  At least it would allow me to freeze the thrust setting until I can tune the PIDs and then move it back over to Channel 6.  Thanks again for the help!!

    • I am using a pixhawk but would I be able to do it with an 8 channel futaba receiver with a PPM encoder connecting the receiver to the pixhawk.  I thought that the RC pass through only maps the corresponding input channel.  Thanks for the help!!

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