Servos¶
The Servos tab configures each physical servo output: center point, travel limits/endpoints, and direction (reversing), on top of whatever mixing rules send input to that output.
Set servo endpoints conservatively at first -- it's easier to increase travel once you've confirmed nothing binds mechanically at the extremes than to diagnose a stalled/straining servo after the fact.
Endpoints and scale¶
Min/Max cap the servo's actual pulse-width travel, to keep the arm off a mechanical stop at either extreme. Scale Neg/Scale Pos are a separate pair of per-side scaling factors (500μs default for a normal 1520μs-center servo, 250μs for a narrow-band 760μs-center one) -- adjust these instead of Min/Max specifically to correct a servo that throws noticeably further on one side than the other.
Rate, Speed, and Reverse¶
Rate is the PWM update frequency for this output -- 50Hz for analog servos (higher can damage them), 100-560Hz for digital servos depending on what the datasheet supports. It only takes effect after Save and reboot, since the rate is set up at boot time, not applied live like most other fields here.
Speed limits how fast the servo is allowed to move, expressed as milliseconds needed for a 60° rotation -- 0 means unlimited. Useful for deliberately slowing a specific output (e.g. retracts) independent of the Mixer rule's own Speed limit on the same output.
Reverse flips direction if a surface moves the wrong way -- check Mixer rule polarity first if only one of several surfaces on the same axis is backwards, since Reverse here and a rule's own Reverse checkbox both flip the same thing from different places.
Geometry Correction¶
Compensates for the non-linear geometry of a servo arm sweeping through an arc -- the further from center, the less each degree of rotation actually moves a pushrod linearly. Only enable it for servos driving a linkage through an arc; leave it off for anything already linear (e.g. a direct belt/rack-driven surface), where there's no arc geometry to correct for.
In-Flight Trim¶
Center points (Mid) don't have to be set from this tab or the CLI -- map Servo Trim Roll, Servo Trim Pitch, or Servo Trim Yaw to a momentary switch on the Adjustments tab (Stepped mode) and nudge them live while flying instead.
Trimming an axis shifts Mid on every servo whose Mixer rule takes its input from that stabilized axis, not just one output -- each servo's own Reverse flag above is respected, so e.g. two ailerons mixed from opposite sides of the same roll input trim toward each other correctly rather than both moving the same raw direction. Servos fed by a raw RC channel, an override, or a logic condition rather than a stabilized axis aren't touched -- the same rule Auto Trim uses for its own capture.
Each axis can move up to ±200μs away from its last saved Mid before hitting the adjustment's own limit. Disarming with a pending trim saves it automatically, the same as any other live-adjusted value, and the ±200μs window then re-baselines to the new center, so there's always fresh headroom to keep trimming across multiple flights rather than being capped by the first save.
Best used in the air, not on the bench
This is meant for trimming while actually flying. Ground use over USB currently fights you on two fronts: this tab won't visibly pick up a center-point change made this way, so there's nothing to confirm/save from the Configurator, and having this tab open over USB blocks arming outright. See firmware issue #17 for current status.
Bus Servos¶
Enabling SBUS Output or FBUS Master on a serial port (see Configuration) adds a second "Bus Servo Configuration" table below the PWM one, covering up to 18 additional outputs -- for digital bus servos wired to that UART instead of individual PWM wires. Each bus output has the same Min/Max/Scale/Speed/Reverse/Geometry Correction fields as a PWM servo, above.
Clone PWM outputs to bus servos¶
Clone PWM outputs to bus servos is ON by default: bus channel 1 mirrors PWM servo 1's final output, bus channel 2 mirrors PWM servo 2, and so on for every bus channel that has a PWM counterpart. This means any mixer built for PWM outputs -- including one generated by the Mixer Setup Wizard for a named model type -- drives the bus servos too, without needing separate mixer rules for them. Bus channels beyond your PWM output count (e.g. channel 9 on a board with 8 PWM outputs) always run their own independent mixer rule regardless of this setting, since there's no PWM output to mirror.
Turn it OFF for a custom model where the bus servos need mixer rules of their own, distinct from the PWM outputs -- for example a different control-surface layout on the bus side, or extra bus channels that don't correspond 1:1 with your PWM outputs. With cloning off, a bus channel's Min/Max/Mid/Scale/Speed/Reverse here and its own rule on the Mixer tab (output numbers past your PWM count) take full effect, exactly like a PWM servo does.
Note
Turning this off doesn't change your existing PWM mixer rules -- it only changes whether the bus outputs also follow them. A common workflow is still to start from the Mixer Setup Wizard for the PWM side, then add or edit rules targeting the bus outputs on the Mixer tab afterward.