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.
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, channel 8 is used for flight modes in Plane and Rover, as is channel 5 in 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.
|RCx_OPTION value||Feature Description||Copter||Plane||Rover|
|0||Do Nothing (Default)||X||X||X|
|3||SIMPLE mode (Copter)||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|
|28||Relay 1 On/off||X||X||X|
|30||Lost Vehicle Sound||X||X||X|
|31||Motor Emergency Stop||X||X||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|
|38||ADSB Avoidance Enable||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|
|59||SIMPLE mode (Rover)||X|
|61||ZIGZAG mode - Save Waypts||X|
|66||Relay 5 On/Off||X||X||X|
|67||Relay 6 On/Off||X||X||X|
|74||Sailboat Motor 3Pos Sw||X|
|75||Surface Tracking Up/Down||X|
Description of Features¶
in descriptions below, LOW and HIGH for a channel refers to PWM <1200us and >1800us, respectively.
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.
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 GPS lock is not active, whereas Plane will always change to the demanded mode and operate as best as it can.
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:
Vehicle will flip on its roll or pitch axis depending upon the pilot’s roll and pitch stick position. See Flip Mode .
|Save Trim||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 shutter will be activated. See more details here.
RangeFinder is disabled when switch is in low position, enabled when in high position.
|Fence||Fence is disabled when switch is in low position, enabled when it high position.|
Turn on automatic leveling in the ACRO flight mode.
Turn on the crop sprayer when switch is pulled high.
Operates the gripper. Switch pulled low releases the gripper, high closes or grabs.
Enables the automatic release of the parachute (this does not immediately trigger the release).
Immediately triggers the release of the parachute as long as the vehicle is not landed or too low.
Switch pulled low disables the parachute. Switch in middle enables the parachute for automatic release. Switch pulled high triggers release of the parachute as long as vehicle is not landed or too low.
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.|
Move the camera mount to its retracted position.
Switch pulled low turns off the first relay, pulled high turns on the first relay.
Deploys or Retracts Landing Gear
|Lost Vehicle Alarm||
Plays the lost copter alarm though the buzzer
|Emergency Stop Motors||
Stops motors immediately (video)
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 its is disabled. When <1200us, it is similar to what is sometimes referred to as Throttle Hold in RC Helicopter terminology for Traditional Helicopters and HeliQuads. For Mulit-copters, it is used as a motor stop function when <1200us. (video).
Invokes the Brake flight mode when switch goes high. Bringing switch back to low will return the vehicle to the mode indicated by the ch5 flight mode switch.
Switch pulled low turns off the second relay, pulled high turns on the second relay.
Switch pulled low turns off the third relay, pulled high turns on the third relay.
Switch pulled low turns off the fourth relay, pulled high turns on the fourth relay.
Invokes the Throw flight mode when switch goes high. Bringing switch back to low will return the vehicle to the mode indicated by the ch5 flight mode switch.
When switch is high, ADSB avoidance (avoidance of manned aircraft) is enabled, otherwise its disabled
Turns on/off Precision Loiter. I.e. holding position above a target in Loiter mode using IR-Lock sensor.
Arms the vehicle if the switch goes high (subject to arming checks). Disarms the vehicle if brought low.
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.
|RC Override Enable||
This is a 3 position switch which enables (high) or disables (low) the use of RC overrides from the Ground Control Station.
This starts the cruise speed and throttle learning sequence on Rover when switched to high. See Tuning Speed and Throttle .
Clears currently loaded mission waypoints.
Inflight compass offset learning. See Automatic Offset Calibration section of Advanced Compass Setup .
Any high to low, or low to high change on this channel will start a tack with opposite direction to the last tack. See Sailboat Configuration and Setup .
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 setup of reverse thrust.
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 three position switch controls the Sailboat motor. Motor is always used when high, never used when low, and as needed, otherwise.
|Surface Tracking Up/Down||
This three position switch determines if surface tracking via rangefinder is toward the ground (low) or ceiling (high), or disabled, otherwise.
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, altitude controllers are modified such that the 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.
This RC channel will drive the output of the MainSail output (
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 end points in the transmitter.