[Bobrcnut]

   From of what I've found here, the prevailing opinion seems to be that I should use PWMSYNC instead of PWM, but most of those posts relate to SimonK or BlHeli ESCs.  Does the PWMSYNC recommendation also apply to older, non-BlHeli ESCs?  This is for a flybarless Trex450 with a Castle Creations Phoenix 35 ESC to be driven by either a CC3D or a Revo.

[TheOtherCliff]

For multicopters, PWMSync is better because there is the smallest possible time between sensor read and control output change for stabilization.

With multicopters the signal can come at a much faster than human speed from sensors, and stabilization control output is sent to ESCs.  With helicopters, the control output is sent to servos, not the single ESC.

Where this could help for helis is the servo signal, not the ESC signal.  To run PWMSync with helicopters, your servos must be able to accept the control pulse 500 times a second (e.g. digital servos).  I don't even know if this is allowed.

For helis, if your servos can't accept 500Hz updates, the easy way is to use PWM@whatever for your servos, where "whatever" is the max update rate of your servos.  I would also use PWM@escwhatever where "escwhatever" is the max update rate of the ESC.  A heli ESC/motor does not change speed very quickly due to huge blade rotational inertia.  Typically the heli ESC is controlled directly by your thumb on the throttle channel, and 1/1000th second (typical) faster just doesn't make a difference with human reaction time and system latency masking any difference.

[Bobrcnut]

Cliff, thanks for the quick response... makes perfect sense, if I can just stop thinking in terms of INAV, and get Castle to give a straight answer about the max. update rate for Phoenix ESCs.

[TheOtherCliff]

Just run the ESC at PWM@50Hz.  The ESC isn't controlled by an inhumanly fast sensor/CPU for stabilization.  The very fastest the vertical control needs to work is your thumb which shouldn't be slower than Revo GPS/baro controlled altitude (unless there was useless jitter).  CC3D doesn't have a baro or GPS flight mode so it really is just your thumb.

(Cyclic already discussed)  In my opinion, the best LP setup would have the collective servo run at PWM@whateveritcanrun and a governor ESC connected directly to a simple PWM@50Hz output controlled by an RC channel knob/slider, that runs the ESC/head speed at a constant speed.

[utoedter]

   From of what I've found here, the prevailing opinion seems to be that I should use PWMSYNC instead of PWM, but most of those posts relate to SimonK or BlHeli ESCs.  Does the PWMSYNC recommendation also apply to older, non-BlHeli ESCs?  This is for a flybarless Trex450 with a Castle Creations Phoenix 35 ESC to be driven by either a CC3D or a Revo.

Hi Bob, as a heli pilot i would really recommend using a BLHELI ESC instead of a normal. Having a constant head speed makes flying very comfortable, you dont have to experiement wih a pitch/throttle curve. And maybe your ESC can be upgraded to BLHELI with a cheap arduino board, 3 wires and a steady hand.

Udo