ardupilot/libraries/AP_Parachute/AP_Parachute.h

/// @file	AP_Parachute.h
/// @brief	Parachute release library
#pragma once

#include <AP_Param/AP_Param.h>
#include <AP_Common/AP_Common.h>
#include <AP_Relay/AP_Relay.h>

#define AP_PARACHUTE_TRIGGER_TYPE_RELAY_0       0
#define AP_PARACHUTE_TRIGGER_TYPE_RELAY_1       1
#define AP_PARACHUTE_TRIGGER_TYPE_RELAY_2       2
#define AP_PARACHUTE_TRIGGER_TYPE_RELAY_3       3
#define AP_PARACHUTE_TRIGGER_TYPE_SERVO         10

#define AP_PARACHUTE_RELEASE_DELAY_MS           500    // delay in milliseconds between call to release() and when servo or relay actually moves.  Allows for warning to user
#define AP_PARACHUTE_RELEASE_DURATION_MS       2000    // when parachute is released, servo or relay stay at their released position/value for 2000ms (2seconds)

#define AP_PARACHUTE_SERVO_ON_PWM_DEFAULT      1300    // default PWM value to move servo to when shutter is activated
#define AP_PARACHUTE_SERVO_OFF_PWM_DEFAULT     1100    // default PWM value to move servo to when shutter is deactivated

#define AP_PARACHUTE_ALT_MIN_DEFAULT            10     // default min altitude the vehicle should have before parachute is released

#define AP_PARACHUTE_CRITICAL_SINK_DEFAULT      0    // default critical sink speed in m/s to trigger emergency parachute

/// @class	AP_Parachute
/// @brief	Class managing the release of a parachute
class AP_Parachute {

public:
    /// Constructor
    AP_Parachute(AP_Relay &relay)
        : _relay(relay)
    {
        // setup parameter defaults
#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
        if (_singleton != nullptr) {
            AP_HAL::panic("Rally must be singleton");
        }
#endif
        _singleton = this;
        AP_Param::setup_object_defaults(this, var_info);
    }

    /* Do not allow copies */
    AP_Parachute(const AP_Parachute &other) = delete;
    AP_Parachute &operator=(const AP_Parachute&) = delete;

    /// enabled - enable or disable parachute release
    void enabled(bool on_off);

    /// enabled - returns true if parachute release is enabled
    bool enabled() const { return _enabled; }

    /// release - release parachute
    void release();

    /// released - true if the parachute has been released (or release is in progress)
    bool released() const { return _released; }
    
    /// release_initiated - true if the parachute release sequence has been initiated (may wait before actual release)
    bool release_initiated() const { return _release_initiated; }

    /// release_in_progress - true if the parachute release sequence is in progress
    bool release_in_progress() const { return _release_in_progress; }
    
    /// update - shuts off the trigger should be called at about 10hz
    void update();
    
    /// critical_sink - returns the configured maximum sink rate to trigger emergency release
    float critical_sink() const { return _critical_sink; }

    /// alt_min - returns the min altitude above home the vehicle should have before parachute is released
    ///   0 = altitude check disabled
    int16_t alt_min() const { return _alt_min; }

    /// set_is_flying - accessor to the is_flying flag
    void set_is_flying(const bool is_flying) { _is_flying = is_flying; }

    // set_sink_rate - set vehicle sink rate
    void set_sink_rate(float sink_rate) { _sink_rate = sink_rate; }

    static const struct AP_Param::GroupInfo        var_info[];

    // get singleton instance
    static AP_Parachute *get_singleton() { return _singleton; }

private:
    static AP_Parachute *_singleton;
    // Parameters
    AP_Int8     _enabled;       // 1 if parachute release is enabled
    AP_Int8     _release_type;  // 0:Servo,1:Relay
    AP_Int16    _servo_on_pwm;  // PWM value to move servo to when shutter is activated
    AP_Int16    _servo_off_pwm; // PWM value to move servo to when shutter is deactivated
    AP_Int16    _alt_min;       // min altitude the vehicle should have before parachute is released
    AP_Int16    _delay_ms;      // delay before chute release for motors to stop
    AP_Float    _critical_sink;      // critical sink rate to trigger emergency parachute

    // internal variables
    AP_Relay   &_relay;         // pointer to relay object from the base class Relay.
    uint32_t    _release_time;  // system time that parachute is ordered to be released (actual release will happen 0.5 seconds later)
    bool        _release_initiated:1;    // true if the parachute release initiated (may still be waiting for engine to be suppressed etc.)
    bool        _release_in_progress:1;  // true if the parachute release is in progress
    bool        _released:1;             // true if the parachute has been released
    bool        _is_flying:1;            // true if the vehicle is flying
    float       _sink_rate;              // vehicle sink rate in m/s
    uint32_t    _sink_time;              // time that the vehicle exceeded critical sink rate
};

namespace AP {
    AP_Parachute *parachute();
};