Auxiliary Functions

This feature is firmware versions 4.0 and higher. In Copter versions before 4.0 similar functions were implemented using the CHx_OPT parameters. See Auxiliary Function Switches (3.6 and earlier) page.

This page describes how to set up additional features which can be invoked from the transmitter’s auxiliary function switches or from external buttons.

Configuring which transmitter channel is used

Any RC input channel can be assigned any auxiliary function. However, the RC channel should not be used by any other function, such as flight mode selection or flight controls. By default, channels 1-4 are used for flight controls (i.e. roll, pitch, throttle, and yaw). The default flight mode channel is 8 for Plane and Rover and 5 for Copter.

Assigning the Feature

The RCx_OPTION parameters control these features. For example, the RC7_OPTION parameter controls which feature is assigned to RC input 7. Each RC channel has its own RCx_OPTION parameter that can be accessed in the full parameter list.

Supported Features

RCx_OPTION value	Feature Description	Copter	Plane	Rover
0	Do Nothing (Default)	X	X	X
2	FLIP	X
3	SIMPLE mode (Copter)	X
4	RTL mode	X	X	X
5	Save Trim	X		X
7	Save Waypoint	X		X
9	Camera Trigger	X	X	X
10	Rangefinder	X
11	Fence	X	X	X
12	ResetToArmedYaw
13	SUPERSIMPLE mode	X
14	Acro Trainer	X
15	Sprayer	X
16	AUTO mode	X	X	X
17	AUTOTUNE mode	X
18	LAND Mode	X
19	Gripper	X	X	X
21	Parachute Enable	X
22	Parachute Release	X	X
23	Parachute 3 Pos Switch	X
24	Reset Auto Mission to start	X	X	X
25	Attitude Controller FF	X
26	Attitude Controller AccLim	X
27	Retract Mount1	X
28	Relay 1 On/off	X	X	X
29	Landing Gear	X	X
30	Lost Vehicle Sound	X	X	X
31	Motor Emergency Stop	X	X	X
32	Motor Interlock	X
33	BRAKE	X
34	Relay 2 On/Off	X	X	X
35	Relay 3 On/Off	X	X	X
36	Relay 4 On/Off	X	X	X
37	THROW mode	X
38	ADSB Avoidance Enable	X
39	Precision Loiter	X
40	Object Avoidance	X		X
41	Arm Disarm (4.1 and before)	X	X	X
42	SMARTRTL mode	X		X
43	Inverted Flight	X	X
44	Winch Enable	X
45	Winch Control	X
46	RC Override Enable	X	X	X
47	Rsvd for custom function	X
48	Rsvd for custom function	X
49	Rsvd for custom function	X
50	Learn Cruise			X
51	MANUAL mode		X	X
52	ACRO mode	X		X
53	STEERING mode			X
54	HOLD mode			X
55	GUIDED mode	X	X	X
56	LOITER mode	X		X
57	FOLLOW mode	X		X
58	Clear Waypoints	X	X	X
59	SIMPLE mode (Rover)			X
60	ZIGZAG mode	X
61	ZIGZAG mode - Save Waypts	X
62	Compass Learn	X	X	X
63	Sailboat Tack			X
64	Reverse Throttle		X
65	GPS Disable	X	X	X
66	Relay 5 On/Off	X	X	X
67	Relay 6 On/Off	X	X	X
68	STABILIZE mode	X
69	POSHOLD mode	X
70	ALTHOLD mode	X	X
71	FLOWHOLD mode	X
72	CIRCLE mode	X	X	X
73	DRIFT mode	X
74	Sailboat Motor 3Pos Sw			X
75	Surface Tracking Up/Down	X
76	STANDBY mode	X
77	TAKEOFF mode		X
78	RunCam Control	X	X	X
79	RunCam OSD Control	X	X	X
80	Viso Align	X
81	Disarm	X	X	X
82	Q_Assist 3Pos Sw		X
83	ZIGZAG Auto	X
84	AIRMODE(not a flight mode)	X	X
85	Generator	X	X	X
86	Non Auto Terrain Follow Disable		x
87	CROW Mode Switch		X
88	Soaring Enable		X
89	Force Flare		X
90	EKF Source Set	X	X	X
91	Airspeed Ratio Calibrate		X
92	FBWA Mode		X
94	VTX Power	X	X	X
95	FBWA_TAILDRAGGER		X
96	MODE_SWITCH_RESET	X	X	X
97	WindVane home dir offset			X
102	Camera Mode Toggle	X	X	X
105	GPS Disable Yaw (testing only!)	X	X	X
106	Disable Airspeed Use	X	X	X
107	Enable Autotuning		X
108	QRTL Mode		X
112	SwitchExternalAHRS	X	X	X
113	Retract Mount2	X
150	CRUISE Mode		X
151	TURTLE Mode	X
152	SIMPLE mode heading reset	X
153	ARM/DISARM (4.2 and higher)	X	X	X
154	ARM/DISARM with AIRMODE on	X	X
155	TRIM RC/SERVO Save		X	X
156	Torqeedo Error Clear			X
157	Force FBWA Long FS Action		X
158	Optflow Calibration	X	X
159	Force Flying State	X
160	WeatherVane Enable		X
161	Turbine Start (Heli)	X
162	Auto Throttle Notch Setup	X	X
163	Mount Lock	X	X	X
164	Pause Streaming Logging	X	X	X
165	ARM/Motor Emergency Stop	X	X	X
166	Camera Record Video	X	X	X
167	Camera Zoom	X	X	X
168	Camera Manual Focus	X	X	X
169	Camera Auto Focus	X	X	X
170	QSTABILIZE mode		X
171	Compass Calibration	X	X	X
172	Battery MPPT Enable	X	X	X
173	Plane AUTO Landing Abort		X
174	Camera Image Tracking	X	X	X
175	Camera Lens	X	X	X
176	VTOL Fwd Throttle disable		X
177	Mount LRF Enable	X	X	X
178	FlightMode Pause/Resume	X
179	ICEngine start / stop		X
180	Autotune_test_gains	X	X

Intended as continuous PWM range control inputs:

RCx_OPTION value	Feature Description	Copter	Plane	Rover
201	ROLL Input	X	X	X
202	PITCH Input	X	X	X
203	THROTTLE Input	X	X	X
204	YAW Input	X	X	X
207	Mainsail			X
208	Flap Control		X
209	Forward Throttle		X
210	Airbrakes		X
211	Walking Robot Height			X
212	Mount1 Roll	X	X	X
213	Mount1 Pitch	X	X	X
214	Mount1 Yaw	X	X	X
215	Mount2 Roll	X	X	X
216	Mount2 Pitch	X	X	X
217	Mount2 Yaw	X	X	X
300-307	Scripting RC channels	X	X	X

Note

201-204 are not implemented, reserved for future use.

Description of Features

Note

in descriptions below, LOW and HIGH for a channel refers to PWM <1200us and >1800us, respectively.

Mode Switches

Any feature ending with “mode” provides the ability to switch the vehicle into that mode by setting the RC channel to high. You can have multiple “mode” option switches and more than one can be high at a time. The last “mode” change switch will determine the current mode, as well as any change of the normal mode switch.

For example, if you have a “LOITER mode” switch active and then an “AUTO mode” switch is switched high, the mode will change to AUTO. Changing the normal flight mode switch will again change the mode to the new flight mode setting, even though both RCx_OPTION mode switches are high. Lowering an active RCx_OPTION mode switch back to low will return the flight mode to whatever is set on the flight mode channel, but only if the current mode matches the mode set by that switch. Otherwise, it will have no effect.

Note

Copter and Rover mode changes are not guaranteed. They may be denied if the conditions required for that mode are not met. For example, changing to LOITER mode in Copter would fail if the GPS lock is not active, whereas in Plane the demanded mode will change and operate as best as it can.

Note

If mapped to a three-position switch then the SUPERSIMPLE mode function will allow SUPERSIMPLE and SIMPLE modes to be enabled using the high and middle switch positions, respectively (a two-position switch will enable/disable SUPERSIMPLE mode only). See here for more details.

Other functions are:

Option	Description
Flip	The vehicle will flip on its roll or pitch axis depending upon the pilot’s roll and pitch stick position. See Flip Mode.
Save Trim	In Rover, a high saves the current steering channel trim, see Save Steering Trim. In Copter, it adjusts the vehicle level position using the current roll and pitch stick inputs. See details here.
Save Waypoint	Save the current location (including altitude) as a waypoint in the mission.If in AUTO mode no waypoint will be saved, instead the vehicle will RTL.
Camera Trigger	The camera shutter will be activated. See more details here.
Range Finder	RangeFinder is disabled when the switch is in a low position, and enabled when in a high position.
Fence	Fence is disabled when the switch is in a low position, and enabled when in a high position.
Acro Trainer	Turn on automatic leveling in the ACRO flight mode.
Sprayer	Turn on the crop sprayer when the switch is pulled high.
Gripper	Operates the gripper. Switch pulled low releases the gripper, high closes or grabs.
Parachute Enable	Enables the automatic release of the parachute (this does not immediately trigger the release).
Parachute Release	Immediately triggers the release of the parachute as long as the vehicle is not landed, or too low.
Parachute 3Pos	Switch pulled low disables the parachute. The switch in the middle position enables the parachute for automatic release. The switch pulled high triggers the release of the parachute as long as the vehicle is not landed, or too low.
Mission Reset	Reset AUTO to run the first mission command in the command list.
AttCon Feed Forward	Turns on/off attitude controllers feed forward. For developers only.
AttCon Accel Limits	Turns on/off attitude controller acceleration limits. For developers only.
Retract Mount1	Move the camera mount to its retracted position.
Retract Mount2	Move the camera mount to its retracted position.
Relay 1 On/Off	Switch pulled low turns off the first relay, pulled high turns on the first relay.
Landing Gear	Deploys or Retracts Landing Gear
Lost Vehicle Alarm	Plays the lost copter alarm through the buzzer
Emergency Stop Motors	Stops motors immediately (video)
Motor Interlock	Motor Interlock controls the way the heliRSC (motor throttle control) output is generated in Traditional Helicopters and HeliQuads. If >1200us, it enables the Motor Interlock function, below it is disabled. When <1200us, it is similar to what is sometimes referred to as Throttle Hold in RC Helicopter terminology. For Mulit-copters, it is used as a motor stop function when <1200us. (video).
Brake	Invokes the Brake flight mode when the switch goes high. Bringing the switch back to low will return the vehicle to the mode indicated by the flight mode switch.
Relay2 On/Off	Switch pulled low turns off the second relay, pulled high turns on the second relay.
Relay3 On/Off	Switch pulled low turns off the third relay, pulled high turns on the third relay.
Relay4 On/Off	Switch pulled low turns off the fourth relay, pulled high turns on the fourth relay.
Throw	Invokes the Throw flight mode when the switch goes high. Bringing the switch back to low will return the vehicle to the mode indicated by the ch5 flight mode switch.
ADSB-Avoidance	When the switch is high, ADSB avoidance (avoidance of manned aircraft) is enabled, otherwise it’s disabled
Precision Loiter	Turns on/off Precision Loiter. (i.e. holding position above a target in Loiter mode using IR-Lock sensor)
Object Avoidance	When the switch is high, avoid objects using Lightware SF40c or TeraRanger Tower. When low, object avoidance is disabled.
Arm/Disarm(4.1 and earlier)	Arms the vehicle if the switch goes high (subject to arming checks). Disarms the vehicle if brought low.

Option	Description
Inverted Flight	Enabling inverted flight only changes how ArduPilot stabilizes the vehicle. It will stabilize it with a roll of 180 degrees from normal whenever inverted flight is enabled in a stabilized mode. Unless the vehicle is capable of inverted flight, do NOT use this option.
Winch Enable	Enables Winch operation. The switch in the low position on this channel relaxes the winch.
Winch Control	Controls the speed and direction of the winch. Low: takeup, Middle: stop, High: unreel
RC Override Enable	This is a 3-position switch that enables (high) or disables (low) the use of RC overrides from the Ground Control Station.
Learn Cruise	This starts the cruise speed and the throttle learning sequence on Rover when switched to high. See Tuning Speed and Throttle.
Clear Waypoints	Clears currently loaded mission waypoints.
Compass Learn	Inflight compass offset learning. See Automatic Offset Calibration section of Advanced Compass Setup.
Sailboat Tack	Any high to low, or low to high change on this channel will start a tack in the opposite direction to the last tack. See Sailboat Configuration and Setup.
Reverse Throttle	When switched high, forces throttle reverse in Plane for steepening descents. Normally, this is controlled by flight mode via the USE_REV_THRUST parameter. See Automatic Landing for more information on the setup of reverse thrust.
GPS Disable	Simulates GPS failure by disabling GPS.
Relay 5 On/Off	Switch pulled low turns off the third relay, pulled high turns on the fifth relay.
Relay 6 On/Off	Switch pulled low turns off the third relay, pulled high turns on the sixth relay.
Sailboat Motor 3Pos Switch	This 3-position switch controls the Sailboat motor. The motor is always used when high, never used when low, and as needed, otherwise.
Surface Tracking Up/Down	This 3-position switch determines if surface tracking via rangefinder is toward the ground (low) or ceiling (high), or disabled, otherwise.
Standby	This puts the autopilot control loops into a soft standby mode so that a parallel,redundant autopilot or companion computer can assume control of the vehicle. The PID loops, position, and altitude controllers are modified such that the autopilot can smoothly resum autopilot can smoothly resume control of the vehicle when standby is subsequently disabled. Switching of outputs or other peripherals must be done by external circuitry.
RunCam Control	Allows starting and stopping video recording of compatible RunCam cameras. See RunCam Camera Support.
RunCam OSD Control	Enables control of RunCam cameras OSDs. See RunCam Camera Support.
VISO Align	Aligns external Visual Odometry with current autopilot AHRS
Disarm	Disarm the vehicle unconditionally and immediately. Unlike Emergency Stop Motors, which waits for DISARM_DELAY in Copter.
Q_Assist 3Pos SW	Low: disable Q_Assist entirely, Middle: Normal Q_Assist operation, High: Q_Assist active at all times. See Assisted Fixed Wing Flight section of Flying a QuadPlane.
ZigZag Mode Auto Enable	Enable automatic zigzag and sprayer in ZIGZAG mode. See ZigZag Mode.
AIRMODE(not a flight mode)	Enables and disables AIRMODE feature. See AirMode
Generator	Mode control for Richenpower Hybrid Power Generator
Non Auto Terrain Follow Disable	Disables Terrain Following in CRUISE and FBWB modes
CROW Mode Switch	Selects between different CROW aileron operating modes
Soaring Enable	Enables Soaring function operating modes
Force Flare	Moves tilt motors to the upright position and optionally sets pitch for flare when landing Tilt Rotor QuadPlanes. Middle: The pilot retains pitch control during a flare. High: Pitch set to LAND_PITCH_DEG. Allows switching
EKF Source Set	between up to three source sets manually for EKF3 (only). See GPS / Non-GPS Transitions.
Airspeed Ratio Calibrate	Activates calibration of airspeed ratio in flight. Best results occur while executing course changes over 360 degrees over time, as in LOITER mode. See Calibrating an Airspeed Sensor.
VTX Power	Allows reading up to a 6-position switch for controlling Video Transmitter Power. See Video Transmitter Support.
FBWA_TAILDRAGGER	Enables FBWA taildragger takeoff mode using elevator to hold tail on the ground until airspeed is reached
MODE_SWITCH_RESET	Forces mode switch to be re-read.
WindVane home direction offset	This is a continuous input channel providing a -45 to +45 degree offset of the initial wind direction when using WNDVN_TYPE = 2.
Camera Mode Toggle	Toggle camera mode (Photo/Video/etc.). Ideally, this should be on a momentary switch since only low to high transitions toggle the camera mode. Used only with Solo gimbals presently.
GPS Disable Yaw	Disables yaw for testing (advanced users only!)
Disable Airspeed Use	Forces Airspeed Use to be disabled for testing in the air.
Enable Autotuning	Allows tuning without entering AUTOTUNE mode. (i.e. if you place the vehicle in LOITER/AUTO with stick mixing enabled, it can autotune while the vehicle is loitering by using sticks, but enabling autotuning can occur in any mode other than MANUAL.)
SwitchExternalAHRS	If EKF3 and an external AHRS module are enabled, high on this switch switches from EKF3 to the external AHRS
SIMPLE mode heading reset	Resets original heading reference to current heading for SIMPLE Mode.
ARM/DISARM (4.2 and higher)	Arms the vehicle if the switch goes high (subject to arming checks). Disarms the vehicle unconditionally if brought low.
ARM/DISARM with AIRMODE on	Arms the vehicle if the switch goes high (subject to arming checks) with AIRMODE active. Airmode RC option switch can subsequently enable or disable if it is configured. Disarms the vehicle unconditionally if brought low.
TRIM RC/SERVO Save	Saves current RC input trim and SERVO output trim for pitch, roll, and yaw in Plane and for Steering in Rover.
Torqeedo Error Clear	Clears error condition in Torqeedo motor controller.
Force FBWA as Long FS Action	Forces mode change to FBWA in Long FS, overriding the FS_LONG_ACTN parameter value for emergency landings beyond RC control range to prevent normal failsafe action from occurring.
Optflow Calibration	Enables calibration of optical flow parameters.
Force Flying	Disables the landing detection heuristic to prevent false landing detections during a mission or manual flight if sudden Z changes can occur due to wind gusts, etc.
WeatherVane Enable	Enables or disables weathervaning in Quadplane VTOL modes.
Turbine Start (Heli)	When armed and RSC is idle, the high position signals the helicopter rotor speed governor to ramp the throttle to full and back to idle, which signals the turbine engine ECU to initiate the start sequence. The switch must be set back low and the aircraft has to be disarmed to re-enable this feature.
Auto Throttle Notch Setup	Allows automatic setup of throttle notch parameters. Set FFT_ENABLE =1, takeoff with switch low, hover 30 seconds with switch high,switch low, and land and notch parameters will have been configured.
Mount Lock	If high, locks the heading of all mounts to earth-frame, otherwise, yaw is heading locked to vehicle heading. If pilot controlled positioning is active, the pilot’s inputs changes the heading target appropriately in whatever frame is selected. Without this switch,it’s vehicle heading.
Pause Streaming Logging	If high, will not log streaming type log messages (sensors, attitudes, EKF, etc.) to allow logging only when desired for autopilots with limited logging capabilities (i.e. no SD card). Events, mode changes, etc. are still logged. Logging is unaffected if the switch is low.
ARM/Motor Emergency Stop	Three position switch. If high, will request arming. If switched to low position, will emergency stop any rotating motor output like the Motor Emergency Stop switch. If switched to middle position,will de-activate the Motor Emergency Stop, but not request an arm condition. This is a safer alternative to ARM/DISARM in that accidental switching to low position will not disarm, and will allow recovery in the air if switched back to middle or high quickly.
Camera Record Video	Controls video recording on some cameras/mounts.
Camera Zoom	Controls camera zoom on some cameras/mounts.
Camera Manual Focus	Changes manual focus on some cameras/mounts.
Camera AutoFocus	Controls autofocus on some cameras/mounts.
Compass Calibration	Switching to high will behave the same as if the Start button for onboard calibration had been pressed. Returning the switch to low will cancel the calibration if still in progress.
Battery MPPT Enable	Enable the Packet Digital MPPT solar panel power monitor
Plane AUTO Mode Landing Abort	If switched to the HIGH position, will abort any landing that is currently in progress while in AUTO mode. This includes the VTOL, or fixed wing, landing phase of any AUTO mission, and the PAYLOAD_PLACE mission command. It does not affect the fixed wing approach phase of a VTOL landing, QLAND or QRTL modes.
Camera Image Tracking	Activate Camera Image Tracking (only supported by ViewPro camera gimbals)
Camera Lens	Select the active camera lens (only supported by ViewPro camera gimbals)
VTOL Fwd Throttle disable	Overrides use of forward throttle in VTOL modes
Mount LRF Enable	Enable(switch high) ranging updates
FlightMode Pause	In Guided/Auto modes, pauses mission
ICEngine start / stop	Controls ICE engine starter output ICE engines
Autotune_test_gains	After autotune,allows selecting tune(high) or pretune gains
ROLL Input	ROLL input channel. (replaces RCMAP)
PITCH Input	PITCH input channel. (replaces RCMAP)
THROTTLE Input	THROTTLE input channel. (replaces RCMAP)
YAW Input	YAW input channel. (replaces RCMAP)
Mainsail	This RC channel will drive the output of the MainSail output ( SERVOx_FUNCTION = 89)instead of being set from the Throttle Input channel (useful if it has an auxiliary motor using that input). See Sailboat Configuration and Setup for more information about the main sail setup.
Flaps	This RC channel provides manual control the amount of FLAP deflection and can also be used in conjunction with Automatic Flaps and/or flaperons. (Replaces the old FLAP_IN_CHANNEL parameter)
Forward Throttle	Manual forward motor throttle in QSTABILIZE, QACRO, and QHOVER modes
Airbrakes	Controls deployment of Airbrakes
Walking Robot Height	Input channel for Walking Robot Height. See Walking Robots.
Mount1 Roll	1st camera gimbal’s roll control
Mount1 Pitch	1st camera gimbal’s pitch control
Mount1 Yaw	1st camera gimbal’s yaw control
Mount2 Roll	2nd camera gimbal’s roll control
Mount2 Pitch	2nd camera gimbal’s pitch control
Mount2 Yaw	2nd camera gimbal’s yaw control
Scripting RC channels	Allows reading a dedicated RC channel for script inputs

Check the channel range

The configured feature will be triggered when the auxiliary switch’s PWM value becomes higher than 1800. It will be deactivated when the value falls below 1200.

You can check the PWM value sent from the transmitter when the switch is high and low using the Mission Planner’s Initial Setup >> Mandatory Hardware >> Radio Calibration screen. If it does not climb higher than 1800 or lower than 1200, it is best to adjust the servo endpoints in the transmitter.