Autopilot Output Functions

All autopilot servo/motor outputs may be mapped to any output function supported by ArduPilot. This page describes how to configure these output channels and what each of the available functions that can be assigned to an output are.

ArduPilot supports up to 32 outputs. These may be via DroneCAN ESCs or directly from autopilot outputs, or a mixture of both.

Note

see the left sidebar menu for major output categories to navigate to desired functions on this page quickly.

The SERVOn_FUNCTION parameters

In the advanced parameter view of your GCS you will find that each SERVO output channel has a SERVOn_FUNCTION parameter. For example, SERVO5_FUNCTION controls the output function of channel 5, SERVO6_FUNCTION controls the output function of channel 6 and so on.

Not all the functions are available in each vehicle. Defaults are set to 0 when firmware for a vehicle type is first loaded. Choosing a frame configuration in Mission Planner during initial setup will set the outputs to the basic typical functions for that frame type. For example, fixed wing plane will set the first four outputs, SERVO1-SERVO4 to Aileron, Elevator, Throttle, and Rudder functions, respectively.

All of these functions may be used on multiple channels. So if you want 3 elevator channels for some reason you can set SERVOn_FUNCTION to 19 on 3 of your output channels.

Configuration

Configuration can be done using the SERVO tab of Mission Planner or by directly setting the SERVOx_FUNCTION parameter for an output.

../_images/rcoutput-mapping.png

For example, if you wished to re-order a Copter quad-x frame’s motors from the kitty-corner default to a more logical clockwise method, make these changes:

  • SERVO1_FUNCTION leave as 33 (aka “motor1”, front-right)

  • SERVO2_FUNCTION change from 34 (aka “motor2”, back-left) to 36 (motor #4, back-right)

  • SERVO3_FUNCTION change from 35 (aka “motor3”, front-left) to 34 (motor #2, back-left)

  • SERVO4_FUNCTION change from 36 (aka “motor4”, back-right) to 35 (motor #3, front-left)

GENERIC FUNCTIONS

Function

ID

Available in:

Disabled

0

Plane, Copter, Rover

RCPassThru

1

Plane, Copter, Rover

RCPassThru1

51

Plane, Copter, Rover

RCPassThru2

52

Plane, Copter, Rover

RCPassThru3

53

Plane, Copter, Rover

RCPassThru4

54

Plane, Copter, Rover

RCPassThru5

55

Plane, Copter, Rover

RCPassThru6

56

Plane, Copter, Rover

RCPassThru7

57

Plane, Copter, Rover

RCPassThru8

58

Plane, Copter, Rover

RCPassThru9

59

Plane, Copter, Rover

RCPassThru10

60

Plane, Copter, Rover

RCPassThru11

61

Plane, Copter, Rover

RCPassThru12

62

Plane, Copter, Rover

RCPassThru13

63

Plane, Copter, Rover

RCPassThru14

64

Plane, Copter, Rover

RCPassThru15

65

Plane, Copter, Rover

RCPassThru16

66

Plane, Copter, Rover

RCIN1Scaled

140

Plane, Copter, Rover

RCIN2Scaled

141

Plane, Copter, Rover

RCIN3Scaled

142

Plane, Copter, Rover

RCIN4Scaled

143

Plane, Copter, Rover

RCIN5Scaled

144

Plane, Copter, Rover

RCIN6Scaled

145

Plane, Copter, Rover

RCIN7Scaled

146

Plane, Copter, Rover

RCIN8Scaled

147

Plane, Copter, Rover

RCIN9Scaled

148

Plane, Copter, Rover

RCIN10Scaled

149

Plane, Copter, Rover

RCIN11Scaled

150

Plane, Copter, Rover

RCIN12Scaled

151

Plane, Copter, Rover

RCIN13Scaled

152

Plane, Copter, Rover

RCIN14Scaled

153

Plane, Copter, Rover

RCIN15Scaled

154

Plane, Copter, Rover

RCIN16Scaled

155

Plane, Copter, Rover

Disabled

For normal operation, the Disabled output function sets the output value of the channel to 0, ie no PWM pulses being sent. The exception to this is when a MAVLink override of the channel or a mission servo set is used. So in some ways “disabled” could be called “mission-controlled”.

When you perform an auto mission you can ask for a servo to be set to a value as part of that mission. In that case you should set the SERVOn_FUNCTION for that channel to Disabled, so that the value doesn’t get changed by another output function immediately after the mission sets the value.

RCPassThru

Setting a channel to RCPassThru means it will output the value that is coming into the board from the corresponding input channel. For example, if SERVO5_FUNCTION is 1 (meaning RCPassThru) then channel 5 output will always be equal to channel 5 input.

Note

The servo output will exactly match the RC input source’s PWM value. RCx_TRIM/_MIN/_MAX and SERVOx_TRIM/_MIN/_MAX has no affect in this mode.

RCPassThru1 to RCPassThru16

This operates the same as RCPassThru explained above. However, instead of the SERVOx output being controlled by the RCx input, any RC input can be assigned to control this output. For example RCPassThru 1 (51) would assign RC Channel 1 input to control the output. So, for output 1, assigning 51 to the SERVO1_FUNCTION is identical to assigning the value of 1 passing RC Channel 1 to the output.

RCIN1Scaled to RCIN16Scaled

This operates similar to RCPassThru1 to RCPassThru16 above. However, instead of exactly passing the received PWM to the output, its is scaled.The RC input’s dead-zone(DZ) is also obeyed.

The upper PWM range from the input trim value to its maximum input is translated to its corresponding output’s trim to maximum parameter values range, and similarly for the ranges below the input’s trim value as shown below:

../_images/rcscaled-io.jpg

PLANE FUNCTIONS (Also applies to QuadPlanes)

Function

ID

Available in:

Aileron

4

Plane

Elevator

19

Plane

Throttle

70

Plane, Copter, Rover

Throttle Left

73

Plane, Copter, Rover

Throttle Right

74

Plane, Copter, Rover

Rudder

21

Plane

Flap

2

Plane

Automatic Flaps

3

Plane

Flaperon Left

24

Plane

Flaperon Right

25

Plane

Elevon Left

77

Plane

Elevon Right

78

Plane

V-Tail Left

79

Plane

V-Tail Right

80

Plane

Differential Spoiler Left1

16

Plane

Differential Spoiler Right1

17

Plane

Differential Spoiler Left2

86

Plane

Differential Spoiler Right2

87

Plane

Ground Steering

26

Plane, Rover

Boost Engine Throttle

81

Copter, QuadPlane

Motor Enable Switch

30

Copter, QuadPlane

Landing Gear

29

Copter, Plane

AirBrakes

110

Plane

Aileron

The Aileron output function provides an aileron output, with its own per-channel trim and range. This is useful when you want to trim each aileron separately, or if your main roll control is setup as ELEVONS, and you also want some normal ailerons.

Elevator

The elevator output function provides an elevator output. Multiple outputs are possible, each with separate per-channel trim and range. This is useful when you want to trim each elevator separately, or if your main pitch control is setup as ELEVONS, and you also want some normal elevator.

Throttle

Typical servo output for motor power control for vehicles. Multiple outputs can be used for multi-engine vehicles. Primary power control output for normal fixed-wing planes, single rotor helicopter, and rovers.

Throttle Left/ Right

In Plane, these outputs are for differential thrust in twin engine aircraft and the amount of yaw affecting the base throttle value is determined by RUDD_DT_GAIN. Also, in Plane’s vectored Tailsitters, these are the motor outputs. In Rover, these outputs are for control of the steering motors in Skid-Steering Rovers. In Copter, theses outputs are used for the Bicopter motors.

Rudder

The rudder output function provides a rudder outputs with its own per-channel trim and range. Separate rudder channels are particularly useful for nose wheel steering where the nose wheel may need to be reversed as compared to the normal rudder channel or for multi-wheel planes.

Flap

When a channel is set as a flap its value comes from the flap rc input channel selected by assigning RCx_FUNCTION = 208 to it and/or from the Automatic Flaps feature. The reason you may want to use this instead of a RCPassThru is that you can setup multiple flap channels with different trims and ranges, and you may want to take advantage of the FLAP_SLEWRATE to limit the speed of flap movement.

Automatic Flaps

The Automatic Flaps output function behaves like the Flap output, except it can also accept automatic flap output control from the TKOFF_FLAP_PCNT and LAND_FLAP_PERCNT parameters, as well as the FLAP_1_SPEED, FLAP_1_PERCNT, FLAP_2_SPEED and FLAP_2_PERCNT parameters. in addition to manual control.

If you have both an RC flap input channel set (RCx_OPTION = 208) and the Automatic Flaps function set, then the amount of flap applied is the higher of the two.

Flaperons

Using SERVOn_FUNCTION 24 and 25 (FlaperonLeft / FlaperonRight) you can setup flaperons, which are ailerons that double as flaps. They are very useful for aircraft which have ailerons but no flaps.

See the Flaperon guide section for more details.

Note that flaperons act like Automatic or normal flaps, described above for the flap component of the output.

Elevon Left/ Right

Provides outputs for Elevons.

V-tail Left/ Right

Provides outputs for V-Tail Planes.

Differential Spoilers Left/Right

See Differential Spoilers section.

Ground Steering

The GroundSteering output function acts much like the rudder output function except that it only acts when the aircraft is below GROUND_STEER_ALT altitude. At altitudes above GROUND_STEER_ALT the output will be the trim value for the channel.

See the separate page on setting up ground steering

Boost Engine Throttle

This output is for throttle control of an auxiliary Booster Motor to add an additional vertical thrust source in Multi-Copter and QuadPlane applications.

Motor Enable Switch

This provides an output that reflects the ARM/DISARM state of the vehicle to control a motor enable/kill switch. When ARMED, it is at SERVOx_MAX pwm, and at SERVOx_MIN pwm when disarmed.

Landing Gear

This output controls the landing gear servo(s) in Copter and Plane. See landing-gear for more information.

Airbrakes

This output is for air brake control. Manual input control is via RCx_OPTION = 210. For more information see Airbrakes.

COPTER / QUADPLANE FUNCTIONS

Function

ID

Available in:

Motor 1

33

Copter, QuadPlane, HeliQuad, Traditional & Dual helicopters

Motor 2

34

Copter, QuadPlane, HeliQuad, Traditional & Dual helicopters

Motor 3

35

Copter, QuadPlane, HeliQuad, Traditional & Dual helicopters

Motor 4

36

Copter, QuadPlane, HeliQuad, Traditional & Dual helicopters

Motor 5

37

Copter, QuadPlane, Dual Helicopter

Motor 6

38

Copter, QuadPlane, Dual Helicopter

Motor 7

39

Copter, QuadPlane

Motor 8

40

Copter, QuadPlane

Motor 9

82

Copter

Motor 10

83

Copter

Motor 11

84

Copter

Motor 12

85

Copter

Motor Tilt

41

QuadPlane

Throttle Left

73

Plane, Copter, Rover

Throttle Right

74

Plane, Copter, Rover

Tilt Motor Left

75

Copter, QuadPlane

Tilt Motor Right

76

Copter, QuadPlane

Tilt Motor Rear

45

QuadPlane

Tilt Motor Rear Left

46

QuadPlane

Tilt Motor Rear Right

47

QuadPlane

Boost Engine Throttle

81

Copter, QuadPlane

Motor Enable Switch

30

Copter, QuadPlane

Parachute Release

27

Copter

Landing Gear

29

Copter, Plane

Winch

88

Copter

Rotor Head Speed

31

Traditional & Dual Helicopter, HeliQuad

Tail Rotor Speed

32

Traditional Helicopter

Motors 1 - 12

These are the Copter and QuadPlane VTOL motor outputs. For Multi-Copters, see Motor Order Diagrams. Or see Traditional Helicopter, or SingleCopter and CoaxCopter, or HeliQuads (Variable Pitch Multicopters).

For QuadPlanes, see QuadPlane Frame setup for motor output configuration.

Throttle Left/ Right

In Plane, these outputs are for differential thrust in twin engine aircraft and the amount of yaw affecting the base throttle value is determined by RUDD_DT_GAIN. Also, in Plane’s vectored Tailsitters, these are the motor outputs. In Rover, these outputs are for control of the steering motors in Skid-Steering Rovers. In Copter, theses outputs are used for the Bicopter motors.

Tilt Motor/ Tilt Motor Left/ Tilt Motor Right/ Tilt Motor Rear/ Tilt Motor Rear Left/ Tilt Motor Rear Right

These outputs control the tilt servos for Tilt Rotor Planes in Plane and Bicopters in Copter.

Boost Engine Throttle

This output is for throttle control of an auxiliary Booster Motor to add an additional vertical thrust source in Multi-Copter and QuadPlane applications.

Motor Enable Switch

This provides an output that reflects the ARM/DISARM state of the vehicle to control a motor enable/kill switch. When ARMED, it is at SERVOx_MAX pwm, and at SERVOx_MIN pwm when disarmed.

Parachute Release

See Parachute section.

Landing Gear

This output controls the landing gear servo(s) in Copter and Plane. See landing-gear for more information.

Winch

This output controls a winch for object delivery in Copter.

Rotor Head Speed

Motor control output for Traditional Helicopter.

Tail Rotor Speed

Output to Traditional Helicopter tail rotor ESC/Governor (future enhancement).

ROVER FUNCTIONS

Function

ID

Available in:

Ground Steering

26

Plane, Rover

Throttle

70

Plane, QuadPlane, Copter, Rover

Throttle Left

73

Plane, Copter, Rover

Throttle Right

74

Plane, Copter, Rover

Main Sail Sheet

89

Rover

Throttle

Typical servo output for motor power control for vehicles. Multiple outputs can be used for multi-engine vehicles. Primary power control output for normal fixed-wing planes, single rotor helicopter, and rovers.

Throttle Left/ Right

In Plane, these outputs are for differential thrust in twin engine aircraft and the amount of yaw affecting the base throttle value is determined by RUDD_DT_GAIN. Also, in Plane’s vectored Tailsitters, these are the motor outputs. In Rover, these outputs are for control of the steering motors in Skid-Steering Rovers. In Copter, theses outputs are used for the Bicopter motors.

Main Sail Sheet

This output is used to control the Main Sail in Rover based Sailboats. See Sailing Vehicle Setup setup for more information.

ANTENNA TRACKER FUNCTIONS

Function

ID

Available in:

Tracker Yaw

71

Antenna Tracker

Tracker Pitch

72

Antenna Tracker

Tracker Yaw/Pitch

These outputs control the pitch and yaw servos for an Antenna Tracker.

CAMERA/GIMBAL FUNCTIONS

Function

ID

Available in:

Mount Yaw

6

Plane, Copter, Rover

Mount Pitch

7

Plane, Copter, Rover

Mount Roll

8

Plane, Copter, Rover

Mount Deploy/Retract

9

Plane, Copter, Rover

Camera Trigger

10

Plane, Copter, Rover

Mount2 Yaw

12

Plane, Copter, Rover

Mount2 Pitch

13

Plane, Copter, Rover

Mount2 Roll

14

Plane, Copter, Rover

Mount2 Deploy/Retract

15

Plane, Copter, Rover

Camera ISO

90

Plane, Copter, Rover

Camera Aperture

91

Plane, Copter, Rover

Camera Focus

92

Plane, Copter, Rover

Camera Shutter Speed

93

Plane, Copter, Rover

Mount Yaw/Pitch/Roll/Deploy

These control the output channels for controlling a servo gimbal. Please see the camera gimbal configuration documentation for details.

The Mount2 options are the same, but control a second camera gimbal.

Camera_trigger

The Camera_trigger output function is used to trigger a camera with a servo. See the camera gimbal documentation for details.

Camera ISO/Aperture/Focus/Shutter Speed

These outputs are used to remotely control the above values for BMMC (Blackmagic Micro Cinema Camera) compatible devices.

INTERNAL COMBUSTION ENGINE FUNCTIONS

Function

ID

Available in:

Ignition

67

Plane, Copter, Rover

Choke

68

reserved for future use

Starter

69

Plane, Copter, Rover

Ignition/Starter/Choke

For control of an internal combustion engine’s spark plug/igniter, starter motor, and choke. See Internal Combustion Engines (ICE).

NEOPIXEL LED STRINGS

Neopixel LEDs/Strings can be controlled using Function IDs 120-123, thereby supporting up to four strings independently controlled. These may be used for ArduPilot notifications and warnings (See Notification Device Configuration ) or controlled via LUA scripting (See Lua Scripts. This is available in all vehicles.

ProfiLEDs

ProfiLEDs can be controlled using Function IDs 129-132, thereby supporting up to three strings independently controlled with a common clock. These may be used for ArduPilot notifications and warnings (See Notification Device Configuration ) or controlled via LUA scripting (See Lua Scripts. This is available in all vehicles. See :ref:

MISCELLANEOUS FUNCTIONS

Function

ID

Available in:

Gripper

28

Plane, Copter, Rover

EggDrop

11

Deprecated

Sprayer Pump

22

Copter

Sprayer Mixer

23

Copter

Output SERVOn_MIN PWM value

134

Plane, Copter, Rover

Output SERVOn_TRIM PWM value

135

Plane, Copter, Rover

Output SERVOn_MAX PWM value

136

Plane, Copter, Rover

Gripper

This is an output for controlling a servo or electromagnetic gripper for holding items for delivery applications. See Grippers (for delivery) for more information.

Sprayer Pump/Mixer

These outputs are controlling a Crop Sprayer.

Output SERVOn MAX/MIN/TRIM

Continuously outputs the parameter value set for that output. Used in button detection. See Buttons

GENERAL PURPOSE LUA SCRIPTING OUTPUTS

Lua Scripts can also directly control autopilot outputs. Using Function IDs 94-109 provides the ability to configure up to 16 of these outputs, if the autopilot is capable. This is available in all vehicles.

INTERNAL CONTROLLER ACCESS

Function

ID

Available in:

RateRoll

124

Copter

RatePitch

125

Copter

RateThrust

126

Copter

RateYaw

127

Copter

These outputs provide the FeedForward terms from the attitude control loops, scaled by the ATC_RAT_x_FF PID parameter values for roll/pitch/yaw for use with external vehicle controllers.

DEFAULT VALUES

Either upon loading the firmware or selecting the frame type, certain default values will be set for the output functions. The user may move these to alternate servo/motor outputs if they desire. The default values are shown below:

VEHICLE TYPE SERVO

1

2

3

4

5

6

7

8

9

10

11

12

MultiCopter

33

34

35

36

37

38

39

40

82

83

84

85

Tricopter

33

34

0

36

0

0

39

0

0

0

0

0

SingleCopter / CoAxialCopter

33

34

35

36

37

38

0

0

0

0

0

0

Traditional Helicopter

33

34

35

36

0

0

0

31

0

0

0

0

Dual Helicopter

33

34

35

36

37

38

0

31

0

0

0

0

HeliQuad

33

34

35

36

0

0

0

31

0

0

0

0

Fixed Wing Plane / Tailsitter

4

19

21

70

0

0

0

0

0

0

0

0

QuadPlane

4

19

21

70

33

34

35

36

0

0

0

0

QuadPlane Tricopter

4

19

21

70

33

34

0

36

0

0

39

0

Rover

26

0

70

0

0

0

0

0

0

0

0

0

Note

Rover Skid Steered vehicles will need to manually change SERVO1 and SERVO3 to Throttle Left and Throttle Right to enable skid steering.