1. 源由

Ardupilot最为主要的一个控制方式就是远程遥控控制。
RC_Channels就是遥控通道实现控制的应用类。该应用类，将RC数据从RCInput按照规定协议获取，经过数据处理、规范化。再使用特定模型应用转化方法进行应用和解释，最终得到控制飞控的应用参数，比如：当前飞行模式。

2. 框架设计

2.1 继承关系

2.1.1 RC_Channel_Copter

继承实现RC_Channel的虚函数。

class RC_Channel_Copter : public RC_Channel
{public:protected:void init_aux_function(aux_func_t ch_option, AuxSwitchPos) override;bool do_aux_function(aux_func_t ch_option, AuxSwitchPos) override;private:void do_aux_function_change_mode(const Mode::Number mode,const AuxSwitchPos ch_flag);void do_aux_function_change_air_mode(const AuxSwitchPos ch_flag);void do_aux_function_change_force_flying(const AuxSwitchPos ch_flag);// called when the mode switch changes position:void mode_switch_changed(modeswitch_pos_t new_pos) override;};

2.1.2 RC_Channels_Copter

继承实现RC_Channels的虚函数。

class RC_Channels_Copter : public RC_Channels
{
public:bool has_valid_input() const override;bool in_rc_failsafe() const override;RC_Channel *get_arming_channel(void) const override;RC_Channel_Copter obj_channels[NUM_RC_CHANNELS];RC_Channel_Copter *channel(const uint8_t chan) override {if (chan >= NUM_RC_CHANNELS) {return nullptr;}return &obj_channels[chan];}// returns true if throttle arming checks should be runbool arming_check_throttle() const override;protected:int8_t flight_mode_channel_number() const override;};

2.1.3 RC_Channels

所有RC通道。

/*class	RC_Channels. Hold the full set of RC_Channel objects
*/
class RC_Channels {
public:friend class SRV_Channels;friend class RC_Channel;// constructorRC_Channels(void);void init(void);// get singleton instancestatic RC_Channels *get_singleton() {return _singleton;}static const struct AP_Param::GroupInfo var_info[];// compatability functions for Plane:static uint16_t get_radio_in(const uint8_t chan) {RC_Channel *c = _singleton->channel(chan);if (c == nullptr) {return 0;}return c->get_radio_in();}static RC_Channel *rc_channel(const uint8_t chan) {return _singleton->channel(chan);}//end compatability functions for Plane// this function is implemented in the child class in the vehicle// codevirtual RC_Channel *channel(uint8_t chan) = 0;// helper used by scripting to convert the above function from 0 to 1 indexeing// range is checked correctly by the underlying channel functionRC_Channel *lua_rc_channel(const uint8_t chan) {return channel(chan -1);}uint8_t get_radio_in(uint16_t *chans, const uint8_t num_channels); // reads a block of chanel radio_in values starting from channel 0// returns the number of valid channelsstatic uint8_t get_valid_channel_count(void);                      // returns the number of valid channels in the last readstatic int16_t get_receiver_rssi(void);                            // returns [0, 255] for receiver RSSI (0 is no link) if present, otherwise -1static int16_t get_receiver_link_quality(void);                         // returns 0-100 % of last 100 packets received at receiver are validbool read_input(void);                                             // returns true if new input has been read instatic void clear_overrides(void);                                 // clears any active overridesstatic bool receiver_bind(const int dsmMode);                      // puts the receiver in bind mode if present, returns true if successstatic void set_override(const uint8_t chan, const int16_t value, const uint32_t timestamp_ms = 0); // set a channels override valuestatic bool has_active_overrides(void);                            // returns true if there are overrides applied that are valid// returns a mask indicating which channels have overrides.  Bit 0// is RC channel 1.  Beware this is not a cheap call.uint16_t get_override_mask() const;class RC_Channel *find_channel_for_option(const RC_Channel::aux_func_t option);bool duplicate_options_exist();RC_Channel::AuxSwitchPos get_channel_pos(const uint8_t rcmapchan) const;void convert_options(const RC_Channel::aux_func_t old_option, const RC_Channel::aux_func_t new_option);void init_aux_all();void read_aux_all();// mode switch handlingvoid reset_mode_switch();virtual void read_mode_switch();virtual bool in_rc_failsafe() const { return true; };virtual bool has_valid_input() const { return false; };virtual RC_Channel *get_arming_channel(void) const { return nullptr; };bool gcs_overrides_enabled() const { return _gcs_overrides_enabled; }void set_gcs_overrides_enabled(bool enable) {_gcs_overrides_enabled = enable;if (!_gcs_overrides_enabled) {clear_overrides();}}enum class Option {IGNORE_RECEIVER         = (1U << 0), // RC receiver modulesIGNORE_OVERRIDES        = (1U << 1), // MAVLink overridesIGNORE_FAILSAFE         = (1U << 2), // ignore RC failsafe bitsFPORT_PAD               = (1U << 3), // pad fport telem outputLOG_RAW_DATA            = (1U << 4), // log rc input bytesARMING_CHECK_THROTTLE   = (1U << 5), // run an arming check for neutral throttleARMING_SKIP_CHECK_RPY   = (1U << 6), // skip the an arming checks for the roll/pitch/yaw channelsALLOW_SWITCH_REV        = (1U << 7), // honor the reversed flag on switchesCRSF_CUSTOM_TELEMETRY   = (1U << 8), // use passthrough data for crsf telemetrySUPPRESS_CRSF_MESSAGE   = (1U << 9), // suppress CRSF mode/rate message for ELRS systemsMULTI_RECEIVER_SUPPORT  = (1U << 10), // allow multiple receiversUSE_CRSF_LQ_AS_RSSI     = (1U << 11), // returns CRSF link quality as RSSI value, instead of RSSICRSF_FM_DISARM_STAR     = (1U << 12), // when disarmed, add a star at the end of the flight mode in CRSF telemetryELRS_420KBAUD           = (1U << 13), // use 420kbaud for ELRS protocol};bool option_is_enabled(Option option) const {return _options & uint32_t(option);}virtual bool arming_check_throttle() const {return option_is_enabled(Option::ARMING_CHECK_THROTTLE);}// returns true if overrides should time out.  If true is returned// then returned_timeout_ms will contain the timeout in// milliseconds, with 0 meaning overrides are disabled.bool get_override_timeout_ms(uint32_t &returned_timeout_ms) const {const float value = _override_timeout.get();if (is_positive(value)) {returned_timeout_ms = uint32_t(value * 1e3f);return true;}if (is_zero(value)) {returned_timeout_ms = 0;return true;}// overrides will not time outreturn false;}// get mask of enabled protocolsuint32_t enabled_protocols() const;// returns true if we have had a direct detach RC receiver, does not include overridesbool has_had_rc_receiver() const { return _has_had_rc_receiver; }// returns true if we have had an override on any channelbool has_had_rc_override() const { return _has_had_override; }/*get the RC input PWM value given a channel number.  Note thatchannel numbers start at 1, as this API is designed for use inLUA*/bool get_pwm(uint8_t channel, uint16_t &pwm) const;uint32_t last_input_ms() const { return last_update_ms; };// method for other parts of the system (e.g. Button and mavlink)// to trigger auxiliary functionsbool run_aux_function(RC_Channel::AUX_FUNC ch_option, RC_Channel::AuxSwitchPos pos, RC_Channel::AuxFuncTriggerSource source) {return rc_channel(0)->run_aux_function(ch_option, pos, source);}// check if flight mode channel is assigned RC option// return true if assignedbool flight_mode_channel_conflicts_with_rc_option() const;// flight_mode_channel_number must be overridden in vehicle specific codevirtual int8_t flight_mode_channel_number() const = 0;// set and get calibrating flag, stops arming if truevoid calibrating(bool b) { gcs_is_calibrating = b; }bool calibrating() { return gcs_is_calibrating; }#if AP_SCRIPTING_ENABLED// get last aux cached value for scripting. Returns false if never set, otherwise 0,1,2bool get_aux_cached(RC_Channel::aux_func_t aux_fn, uint8_t &pos);
#endif// get failsafe timeout in millisecondsuint32_t get_fs_timeout_ms() const { return MAX(_fs_timeout * 1000, 100); }protected:void new_override_received() {has_new_overrides = true;_has_had_override = true;}private:static RC_Channels *_singleton;// this static arrangement is to avoid static pointers in AP_Param tablesstatic RC_Channel *channels;uint32_t last_update_ms;bool has_new_overrides;bool _has_had_rc_receiver; // true if we have had a direct detach RC receiver, does not include overridesbool _has_had_override; // true if we have had an override on any channelAP_Float _override_timeout;AP_Int32  _options;AP_Int32  _protocols;AP_Float _fs_timeout;RC_Channel *flight_mode_channel() const;// Allow override by default at startbool _gcs_overrides_enabled = true;// true if GCS is performing a RC calibrationbool gcs_is_calibrating;#if AP_SCRIPTING_ENABLED// bitmask of last aux function value, 2 bits per function// value 0 means never set, otherwise level+1HAL_Semaphore aux_cache_sem;Bitmask<unsigned(RC_Channel::AUX_FUNC::AUX_FUNCTION_MAX)*2> aux_cached;void set_aux_cached(RC_Channel::aux_func_t aux_fn, RC_Channel::AuxSwitchPos pos);
#endif
};

2.1.4 RC_Channel

单独一个RC通道。

/// @class	RC_Channel
/// @brief	Object managing one RC channel
class RC_Channel {
public:friend class SRV_Channels;friend class RC_Channels;// ConstructorRC_Channel(void);enum class ControlType {ANGLE = 0,RANGE = 1,};// setup the control preferencesvoid        set_range(uint16_t high);uint16_t    get_range() const { return high_in; }void        set_angle(uint16_t angle);bool        get_reverse(void) const;void        set_default_dead_zone(int16_t dzone);uint16_t    get_dead_zone(void) const { return dead_zone; }// get the center stick position expressed as a control_in valueint16_t     get_control_mid() const;// read input from hal.rcin - create a control_in valuebool        update(void);// calculate an angle given dead_zone and trim. This is used by the quadplane code// for hover throttleint16_t     pwm_to_angle_dz_trim(uint16_t dead_zone, uint16_t trim) const;// return a normalised input for a channel, in range -1 to 1,// centered around the channel trim. Ignore deadzone.float       norm_input() const;// return a normalised input for a channel, in range -1 to 1,// centered around the channel trim. Take into account the deadzonefloat       norm_input_dz() const;// return a normalised input for a channel, in range -1 to 1,// ignores trim and deadzonefloat       norm_input_ignore_trim() const;// returns true if input is within deadzone of minbool        in_min_dz() const;uint8_t     percent_input() const;static const struct AP_Param::GroupInfo var_info[];// return true if input is within deadzone of trimbool       in_trim_dz() const;int16_t    get_radio_in() const { return radio_in;}void       set_radio_in(int16_t val) {radio_in = val;}int16_t    get_control_in() const { return control_in;}void       set_control_in(int16_t val) { control_in = val;}void       clear_override();void       set_override(const uint16_t v, const uint32_t timestamp_ms);bool       has_override() const;float    stick_mixing(const float servo_in);// get control input with zero deadzoneint16_t    get_control_in_zero_dz(void) const;int16_t    get_radio_min() const {return radio_min.get();}int16_t    get_radio_max() const {return radio_max.get();}int16_t    get_radio_trim() const { return radio_trim.get();}void       set_and_save_trim() { radio_trim.set_and_save_ifchanged(radio_in);}// set and save trim if changedvoid       set_and_save_radio_trim(int16_t val) { radio_trim.set_and_save_ifchanged(val);}// check if any of the trim/min/max param are configured, this would indicate that the user has done a calibration at somepointbool       configured() { return radio_min.configured() || radio_max.configured() || radio_trim.configured(); }ControlType get_type(void) const { return type_in; }AP_Int16    option; // e.g. activate EPM gripper / enable fence// auxiliary switch supportvoid init_aux();bool read_aux();// Aux Switch enumerationenum class AUX_FUNC {DO_NOTHING =           0, // aux switch disabledFLIP =                 2, // flipSIMPLE_MODE =          3, // change to simple modeRTL =                  4, // change to RTL flight modeSAVE_TRIM =            5, // save current position as levelSAVE_WP =              7, // save mission waypoint or RTL if in auto modeCAMERA_TRIGGER =       9, // trigger camera servo or relayRANGEFINDER =         10, // allow enabling or disabling rangefinder in flight which helps avoid surface tracking when you are far above the groundFENCE =               11, // allow enabling or disabling fence in flightRESETTOARMEDYAW =     12, // UNUSEDSUPERSIMPLE_MODE =    13, // change to simple mode in middle, super simple at topACRO_TRAINER =        14, // low = disabled, middle = leveled, high = leveled and limitedSPRAYER =             15, // enable/disable the crop sprayerAUTO =                16, // change to auto flight modeAUTOTUNE =            17, // auto tuneLAND =                18, // change to LAND flight modeGRIPPER =             19, // Operate cargo grippers low=off, middle=neutral, high=onPARACHUTE_ENABLE  =   21, // Parachute enable/disablePARACHUTE_RELEASE =   22, // Parachute releasePARACHUTE_3POS =      23, // Parachute disable, enable, release with 3 position switchMISSION_RESET =       24, // Reset auto mission to start from first commandATTCON_FEEDFWD =      25, // enable/disable the roll and pitch rate feed forwardATTCON_ACCEL_LIM =    26, // enable/disable the roll, pitch and yaw accel limitingRETRACT_MOUNT1 =      27, // Retract Mount1RELAY =               28, // Relay pin on/off (only supports first relay)LANDING_GEAR =        29, // Landing gear controllerLOST_VEHICLE_SOUND =  30, // Play lost vehicle soundMOTOR_ESTOP =         31, // Emergency Stop SwitchMOTOR_INTERLOCK =     32, // Motor On/Off switchBRAKE =               33, // Brake flight modeRELAY2 =              34, // Relay2 pin on/offRELAY3 =              35, // Relay3 pin on/offRELAY4 =              36, // Relay4 pin on/offTHROW =               37, // change to THROW flight modeAVOID_ADSB =          38, // enable AP_Avoidance libraryPRECISION_LOITER =    39, // enable precision loiterAVOID_PROXIMITY =     40, // enable object avoidance using proximity sensors (ie. horizontal lidar)ARMDISARM_UNUSED =    41, // UNUSEDSMART_RTL =           42, // change to SmartRTL flight modeINVERTED  =           43, // enable inverted flightWINCH_ENABLE =        44, // winch enable/disableWINCH_CONTROL =       45, // winch controlRC_OVERRIDE_ENABLE =  46, // enable RC OverrideUSER_FUNC1 =          47, // user function #1USER_FUNC2 =          48, // user function #2USER_FUNC3 =          49, // user function #3LEARN_CRUISE =        50, // learn cruise throttle (Rover)MANUAL       =        51, // manual modeACRO         =        52, // acro modeSTEERING     =        53, // steering modeHOLD         =        54, // hold modeGUIDED       =        55, // guided modeLOITER       =        56, // loiter modeFOLLOW       =        57, // follow modeCLEAR_WP     =        58, // clear waypointsSIMPLE       =        59, // simple modeZIGZAG       =        60, // zigzag modeZIGZAG_SaveWP =       61, // zigzag save waypointCOMPASS_LEARN =       62, // learn compass offsetsSAILBOAT_TACK =       63, // rover sailboat tackREVERSE_THROTTLE =    64, // reverse throttle inputGPS_DISABLE  =        65, // disable GPS for testingRELAY5 =              66, // Relay5 pin on/offRELAY6 =              67, // Relay6 pin on/offSTABILIZE =           68, // stabilize modePOSHOLD   =           69, // poshold modeALTHOLD   =           70, // althold modeFLOWHOLD  =           71, // flowhold modeCIRCLE    =           72, // circle modeDRIFT     =           73, // drift modeSAILBOAT_MOTOR_3POS = 74, // Sailboat motoring 3posSURFACE_TRACKING =    75, // Surface tracking upwards or downwardsSTANDBY  =            76, // Standby modeTAKEOFF   =           77, // takeoffRUNCAM_CONTROL =      78, // control RunCam deviceRUNCAM_OSD_CONTROL =  79, // control RunCam OSDVISODOM_ALIGN =       80, // align visual odometry camera's attitude to AHRSDISARM =              81, // disarm vehicleQ_ASSIST =            82, // disable, enable and force Q assistZIGZAG_Auto =         83, // zigzag auto switchAIRMODE =             84, // enable / disable airmode for copterGENERATOR   =         85, // generator controlTER_DISABLE =         86, // disable terrain following in CRUISE/FBWB modesCROW_SELECT =         87, // select CROW mode for diff spoilers;high disables,mid forces progressiveSOARING =             88, // three-position switch to set soaring modeLANDING_FLARE =       89, // force flare, throttle forced idle, pitch to LAND_PITCH_CD, tilts upEKF_POS_SOURCE =      90, // change EKF position source between primary, secondary and tertiary sourcesARSPD_CALIBRATE=      91, // calibrate airspeed ratio FBWA =                92, // Fly-By-Wire-ARELOCATE_MISSION =    93, // used in separate branch MISSION_RELATIVEVTX_POWER =           94, // VTX power levelFBWA_TAILDRAGGER =    95, // enables FBWA taildragger takeoff mode. Once this feature is enabled it will stay enabled until the aircraft goes above TKOFF_TDRAG_SPD1 airspeed, changes mode, or the pitch goes above the initial pitch when this is engaged or goes below 0 pitch. When enabled the elevator will be forced to TKOFF_TDRAG_ELEV. This option allows for easier takeoffs on taildraggers in FBWA mode, and also makes it easier to test auto-takeoff steering handling in FBWA.MODE_SWITCH_RESET =   96, // trigger re-reading of mode switchWIND_VANE_DIR_OFSSET= 97, // flag for windvane direction offset input, used with windvane type 2TRAINING            = 98, // mode trainingAUTO_RTL =            99, // AUTO RTL via DO_LAND_START// entries from 100-150  are expected to be developer// options used for testingKILL_IMU1 =          100, // disable first IMU (for IMU failure testing)KILL_IMU2 =          101, // disable second IMU (for IMU failure testing)CAM_MODE_TOGGLE =    102, // Momentary switch to cycle camera modesEKF_LANE_SWITCH =    103, // trigger lane switch attemptEKF_YAW_RESET =      104, // trigger yaw reset attemptGPS_DISABLE_YAW =    105, // disable GPS yaw for testingDISABLE_AIRSPEED_USE = 106, // equivalent to AIRSPEED_USE 0FW_AUTOTUNE =          107, // fixed wing auto tuneQRTL =               108, // QRTL modeCUSTOM_CONTROLLER =  109,  // use Custom ControllerKILL_IMU3 =          110, // disable third IMU (for IMU failure testing)LOWEHEISER_STARTER = 111,  // allows for manually running starter// if you add something here, make sure to update the documentation of the parameter in RC_Channel.cpp!// also, if you add an option >255, you will need to fix duplicate_options_exist// options 150-199 continue user rc switch optionsCRUISE =             150,  // CRUISE modeTURTLE =             151,  // Turtle mode - flip over after crashSIMPLE_HEADING_RESET = 152, // reset simple mode reference heading to currentARMDISARM =          153, // arm or disarm vehicleARMDISARM_AIRMODE =  154, // arm or disarm vehicle enabling airmodeTRIM_TO_CURRENT_SERVO_RC = 155, // trim to current servo and RCTORQEEDO_CLEAR_ERR = 156, // clear torqeedo errorEMERGENCY_LANDING_EN = 157, //Force long FS action to FBWA for landing out of rangeOPTFLOW_CAL =        158, // optical flow calibrationFORCEFLYING =        159, // enable or disable land detection for GPS based manual modes preventing land detection and maintainting set_throttle_mix_maxWEATHER_VANE_ENABLE = 160, // enable/disable weathervaningTURBINE_START =      161, // initialize turbine start sequenceFFT_NOTCH_TUNE =     162, // FFT notch tuning functionMOUNT_LOCK =         163, // Mount yaw lock vs followLOG_PAUSE =          164, // Pauses logging if under logging rate controlARM_EMERGENCY_STOP = 165, // ARM on high, MOTOR_ESTOP on lowCAMERA_REC_VIDEO =   166, // start recording on high, stop recording on lowCAMERA_ZOOM =        167, // camera zoom high = zoom in, middle = hold, low = zoom outCAMERA_MANUAL_FOCUS = 168,// camera manual focus.  high = long shot, middle = stop focus, low = close shotCAMERA_AUTO_FOCUS =  169, // camera auto focusQSTABILIZE =         170, // QuadPlane QStabilize modeMAG_CAL =            171, // Calibrate compasses (disarmed only)BATTERY_MPPT_ENABLE = 172,// Battery MPPT Power enable. high = ON, mid = auto (controlled by mppt/batt driver), low = OFF. This effects all MPPTs.PLANE_AUTO_LANDING_ABORT = 173, // Abort Glide-slope or VTOL landing during payload place or do_land type mission itemsCAMERA_IMAGE_TRACKING = 174, // camera image trackingCAMERA_LENS =        175, // camera lens selectionVFWD_THR_OVERRIDE =  176, // force enabled VTOL forward throttle method// inputs from 200 will eventually used to replace RCMAPROLL =               201, // roll inputPITCH =              202, // pitch inputTHROTTLE =           203, // throttle pilot inputYAW =                204, // yaw pilot inputMAINSAIL =           207, // mainsail inputFLAP =               208, // flap inputFWD_THR =            209, // VTOL manual forward throttleAIRBRAKE =           210, // manual airbrake controlWALKING_HEIGHT =     211, // walking robot height inputMOUNT1_ROLL =        212, // mount1 roll inputMOUNT1_PITCH =       213, // mount1 pitch inputMOUNT1_YAW =         214, // mount1 yaw inputMOUNT2_ROLL =        215, // mount2 roll inputMOUNT2_PITCH =       216, // mount3 pitch inputMOUNT2_YAW =         217, // mount4 yaw inputLOWEHEISER_THROTTLE= 218,  // allows for throttle on slider// inputs 248-249 are reserved for the Skybrush fork at// https://github.com/skybrush-io/ardupilot// inputs for the use of onboard lua scriptingSCRIPTING_1 =        300,SCRIPTING_2 =        301,SCRIPTING_3 =        302,SCRIPTING_4 =        303,SCRIPTING_5 =        304,SCRIPTING_6 =        305,SCRIPTING_7 =        306,SCRIPTING_8 =        307,// this must be higher than any aux function aboveAUX_FUNCTION_MAX =   308,};typedef enum AUX_FUNC aux_func_t;// auxiliary switch handling (n.b.: we store this as 2-bits!):enum class AuxSwitchPos : uint8_t {LOW,       // indicates auxiliary switch is in the low position (pwm <1200)MIDDLE,    // indicates auxiliary switch is in the middle position (pwm >1200, <1800)HIGH       // indicates auxiliary switch is in the high position (pwm >1800)};enum class AuxFuncTriggerSource : uint8_t {INIT,RC,BUTTON,MAVLINK,MISSION,SCRIPTING,};AuxSwitchPos get_aux_switch_pos() const;// wrapper function around do_aux_function which allows us to logbool run_aux_function(aux_func_t ch_option, AuxSwitchPos pos, AuxFuncTriggerSource source);#if AP_RC_CHANNEL_AUX_FUNCTION_STRINGS_ENABLEDconst char *string_for_aux_function(AUX_FUNC function) const;const char *string_for_aux_pos(AuxSwitchPos pos) const;
#endif// pwm value under which we consider that Radio value is invalidstatic const uint16_t RC_MIN_LIMIT_PWM = 800;// pwm value above which we consider that Radio value is invalidstatic const uint16_t RC_MAX_LIMIT_PWM = 2200;// pwm value above which we condider that Radio min value is invalidstatic const uint16_t RC_CALIB_MIN_LIMIT_PWM = 1300;// pwm value under which we condider that Radio max value is invalidstatic const uint16_t RC_CALIB_MAX_LIMIT_PWM = 1700;// pwm value above which the switch/button will be invoked:static const uint16_t AUX_SWITCH_PWM_TRIGGER_HIGH = 1800;// pwm value below which the switch/button will be disabled:static const uint16_t AUX_SWITCH_PWM_TRIGGER_LOW = 1200;// pwm value above which the option will be invoked:static const uint16_t AUX_PWM_TRIGGER_HIGH = 1700;// pwm value below which the option will be disabled:static const uint16_t AUX_PWM_TRIGGER_LOW = 1300;protected:virtual void init_aux_function(aux_func_t ch_option, AuxSwitchPos);// virtual function to be overridden my subclassesvirtual bool do_aux_function(aux_func_t ch_option, AuxSwitchPos);void do_aux_function_armdisarm(const AuxSwitchPos ch_flag);void do_aux_function_avoid_adsb(const AuxSwitchPos ch_flag);void do_aux_function_avoid_proximity(const AuxSwitchPos ch_flag);void do_aux_function_camera_trigger(const AuxSwitchPos ch_flag);bool do_aux_function_record_video(const AuxSwitchPos ch_flag);bool do_aux_function_camera_zoom(const AuxSwitchPos ch_flag);bool do_aux_function_camera_manual_focus(const AuxSwitchPos ch_flag);bool do_aux_function_camera_auto_focus(const AuxSwitchPos ch_flag);bool do_aux_function_camera_image_tracking(const AuxSwitchPos ch_flag);bool do_aux_function_camera_lens(const AuxSwitchPos ch_flag);void do_aux_function_runcam_control(const AuxSwitchPos ch_flag);void do_aux_function_runcam_osd_control(const AuxSwitchPos ch_flag);void do_aux_function_fence(const AuxSwitchPos ch_flag);void do_aux_function_clear_wp(const AuxSwitchPos ch_flag);void do_aux_function_gripper(const AuxSwitchPos ch_flag);void do_aux_function_lost_vehicle_sound(const AuxSwitchPos ch_flag);void do_aux_function_mission_reset(const AuxSwitchPos ch_flag);void do_aux_function_rc_override_enable(const AuxSwitchPos ch_flag);void do_aux_function_relay(uint8_t relay, bool val);void do_aux_function_sprayer(const AuxSwitchPos ch_flag);void do_aux_function_generator(const AuxSwitchPos ch_flag);void do_aux_function_fft_notch_tune(const AuxSwitchPos ch_flag);typedef int8_t modeswitch_pos_t;virtual void mode_switch_changed(modeswitch_pos_t new_pos) {// no action by default (e.g. Tracker, Sub, who do their own thing)};private:// pwm is stored hereint16_t     radio_in;// value generated from PWM normalised to configured scaleint16_t    control_in;AP_Int16    radio_min;AP_Int16    radio_trim;AP_Int16    radio_max;AP_Int8     reversed;AP_Int16    dead_zone;ControlType type_in;int16_t     high_in;// the input channel this corresponds touint8_t     ch_in;// overridesuint16_t override_value;uint32_t last_override_time;int16_t pwm_to_angle() const;int16_t pwm_to_angle_dz(uint16_t dead_zone) const;int16_t pwm_to_range() const;int16_t pwm_to_range_dz(uint16_t dead_zone) const;bool read_3pos_switch(AuxSwitchPos &ret) const WARN_IF_UNUSED;bool read_6pos_switch(int8_t& position) WARN_IF_UNUSED;// Structure used to detect and debounce switch changesstruct {int8_t debounce_position = -1;int8_t current_position = -1;uint32_t last_edge_time_ms;} switch_state;void reset_mode_switch();void read_mode_switch();bool debounce_completed(int8_t position);#if AP_RC_CHANNEL_AUX_FUNCTION_STRINGS_ENABLED// Structure to lookup switch change announcementsstruct LookupTable{AUX_FUNC option;const char *announcement;};static const LookupTable lookuptable[];
#endif
};

2.2 启动代码

Copter::init_ardupilot└──> RC_Channels::init

2.3 任务代码

SCHED_TASK(rc_loop,              250,    130,  3),└──> Copter::rc_loop└──> Copter::read_radio└──> RC_Channels::read_input

3. 重要例程

3.1 RC_Channels

RC通道唯一实例对象初始化。

RC_Channels::RC_Channels││  // set defaults from the parameter table├──> AP_Param::setup_object_defaults(this, var_info)││  // only one instance├──> <_singleton != nullptr>│   └──> AP_HAL::panic("RC_Channels must be singleton")└──> _singleton = this

3.2 init

初始化所有RC通道。

RC_Channels::init││   // setup ch_in on channels├──> <for (uint8_t i=0 i<NUM_RC_CHANNELS i++)>│   └──> channel(i)->ch_in = i└──> init_aux_all()

RC_Channels::init_aux_all├──> <for (uint8_t i=0 i<NUM_RC_CHANNELS i++)>│   ├──> RC_Channel *c = channel(i)│   ├──> <c == nullptr>│   │   └──> continue│   └──> c->init_aux()└──> reset_mode_switch()

3.3 read_input

// update all the input channels
RC_Channels::read_input││   //check rc new input├──> <hal.rcin->new_input()) {│   └──> _has_had_rc_receiver = true├──> < else if (!has_new_overrides) >│   └──> return false├──> has_new_overrides = false│├──> last_update_ms = AP_HAL::millis()││   //update all rc channels├──> bool success = false├──> <for (uint8_t i=0 i<NUM_RC_CHANNELS i++)>│   └──> success |= channel(i)->update()└──> return success

3.4 update

RC遥控数据，详见：ArduPilot开源代码之RCInput

// read input from hal.rcin or overrides
RC_Channel::update││   //update rc channel in├──> <has_override() && !rc().option_is_enabled(RC_Channels::Option::IGNORE_OVERRIDES)>│   └──> radio_in = override_value├──> < else if (rc().has_had_rc_receiver() && !rc().option_is_enabled(RC_Channels::Option::IGNORE_RECEIVER))>│   └──> radio_in = hal.rcin->read(ch_in)├──> < else >│   └──> return false││   //calculate deadzone├──> <type_in == ControlType::RANGE>│   └──> control_in = pwm_to_range()├──> < else >│   └──> control_in = pwm_to_angle() // // ControlType::ANGLE└──> return true

4. 总结

从整个代码设计逻辑上可以分析出以下几点：

1. RC_Channels_Copter完善Copter模型RC_Channels类的应用实现；
2. RC_Channel_Copter完善Copter模型RC_Channel类的应用实现；
3. RC原始遥控通道数据来源于RC_Channel类的update方法；
4. RC遥控协议的解析主要在RCInput完成；

RC数据流方向：RCInput ==》 RC_Channel + RC_Channel_Copter ==》 RC_Channels + RC_Channels_Copter

5. 参考资料

【1】ArduPilot开源飞控系统之简单介绍
【2】ArduPilot之开源代码Task介绍
【3】ArduPilot飞控启动&运行过程简介
【4】ArduPilot之开源代码Library&Sketches设计
【5】ArduPilot之开源代码Sensor Drivers设计