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add note on auto servo range for DShot #2358

Closed tridge closed 4 years ago

tridge commented 4 years ago

when we setup motors using the SERVO_BLHELI options we automatically force output channels setup using SERVO_BLHELI options to use a range of 1000 to 2000. This can confuse users so we need to document it. See this discussion: https://discuss.ardupilot.org/t/plane-4-0-release/47188/205 and this issue: https://github.com/ArduPilot/ardupilot/issues/13092 Note that we force the trim to either 1000 or 1500 depending on whether the output is marked as reversible.

Hwurzburg commented 4 years ago

done

Rolf-G commented 4 years ago

BLHELI-telemetry in non-vectored tri-motor VTOLs works with SERVO_BLH_AUTO set 0 and instead SERVO_BLH_MASK with a bitmask of the actually outputs connected to BLHELI-ESCs.

Rolf-G commented 4 years ago

@Hwurzburg , @tridge as a result of the above, i suggest adding the following section in the wiki on page https://ardupilot.org/plane/docs/guide-tilt-rotor.html after the section "Vectored Yaw"

Non-Vectored Yaw

Non-Vectored yaw aircraft (Q_TILT_TYPE 0 or 1) needs a tilt servo for the rear motor for yaw control.

You need to setup your two front tilt servos both with SERVOn_FUNCTION=41 and also your rear servo for yaw control with SERVOn_FUNCTION=39 (no literal error).

Note that if you want to use BLHELI ESCs with telemetry in non-vectored tri-tilts, you must not set BLHELI to 1. Set SERVO_BLH_MASK to the output-bitmask of the servo-channels actually connected BLHELI-ESCs. E.g. SERVO_BLH_MASK=1792 for Servo 9,10,11 (the first three aux-outputs of a pixhawk1). You also need to setup Q_M_PWM_TYPE to 4 (DShot 150).