Tricopter yaw servo reversed


Does anyone know how to reverse the output from APM to the servo (tricopter)? I
think that I can fix this by rotating the servo, but it might be easier to just
change something in the code, since the DIP switches are not used anymore.


**The APM is mounted correctly; it's only the output to the yaw servo that is reversed
i.e. stabilize corrections are reversed, but manual input from the transmitter is correct.**

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  • Hey, yes you can reverse the yaw. Did you come right?


    OK. Just for completeness, and to make it easier for others coming across this. This is the code fix:


    // servo Yaw

    if(g.rc_4.get_reverse() == true)
    APM_RC.OutputCh(CH_7, ( (-1 * (g.rc_4.radio_out - g.rc_4.radio_trim) ) + g.rc_4.radio_trim ) );

    APM_RC.OutputCh(CH_7, g.rc_4.radio_out);


    At line 831 in 2.0.38 in the ArduCopterMega.pde tab

    This should let you reverse channel 4 in the planner by putting in a '-1' which will reverse the way the copter compensates with the yaw gyro.

    Thank you Don for the fix!

  • i have try to change CH4_rev to -1, the ruder can reverse.

    but my 3Cs is still rotate yaw to left

    I think, i must reverse the yaw gyro.

    i use prop. CCW for left front and back. and CW for right front

    any idea?
  • Ahhh! Just got it to work! You need to reverse the RC4 channel NOT the RC7 -- RC4 is the input for yaw on a tricopter. You reverse the channel by replacing 1 with -1 as per the APM manual. It would be nice if a revision of this page was in the ACM manual.
  • I tried changing the value to/from: 1, 0, -1 -- there is no diffrnce between either of them. Maybe this function is disabled/not used in ACM2?
  • It's an anolog servo. Where about is the RC7_REV - I can't seem to find it?
  • can we set reverse servo from configurator AMP by change value of RC7_REV?
  • Developer


    To keep things simple and if you have a digital servo, then you can program it for reverse operation.

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