Hi all,

I've just dusted off my S900 with Pixhawk 2 and want to get it back in the air. But I'm having some issues with the lower end of the throttle range, which when tied with the fact this is massively overpowered with no payload, means that I'm having some hairy takeoffs and landings.

Basically I'm not getting any motor response until the throttle stick gets to almost halfway, then I get normal throttle control but I can only use the top half of the stick range to control the drone.

Here's what the numbers are showing in Mission Planner:

Drone disarmed (throttle stick fully down)

RC3 In = 1094

RC3 Out = 1094

Armed (throttle stick fully down)

RC3 In = 1094

RC3 Out = 1169 (which is governed by the MOT_SPIN_ARM setting at 9%)

Motors start idling

Increasing throttle to almost halfway

RC3 In = 1094 up to about 1430

RC3 Out = 1169

Motors still just idling

Increase throttle stick more

RC3 In = 1430 up to max

RC3 Out = increase proportionately from 1169

Motors speed up according to RC3 Out value. Haven't been able to test how it behaves over the full range because I'm testing indoors.

Can anyone suggest why I might not have use of the lower half of the throttle stick range?

Regarding my setup:

Running APM:Copter V3.5.3

My understanding is that these DJI ESCs cannot be calibrated.

I have seen reference to people changing the min max of the throttle output to account for the DJI ESCs top and bottom deadzones, but I can't find verified numbers/advice on that, and I don't think this will help this issue, as the problem seems to be with how the pixhawk converts my throttle movements into RC3 Out signals to the ESC.

Thanks in advance, Joel

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