ardupilot/libraries/AP_Compass/Compass.h

/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
#ifndef Compass_h
#define Compass_h

#include <inttypes.h>
#include "../AP_Common/AP_Common.h"
#include "../AP_Math/AP_Math.h"
#include "../AP_Declination/AP_Declination.h" // ArduPilot Mega Declination Helper Library

// compass product id
#define AP_COMPASS_TYPE_UNKNOWN  0x00
#define AP_COMPASS_TYPE_HIL      0x01
#define AP_COMPASS_TYPE_HMC5843  0x02
#define AP_COMPASS_TYPE_HMC5883L 0x03

class Compass
{
public:
	int16_t			product_id;     /// product id
	int16_t         mag_x;          ///< magnetic field strength along the X axis
	int16_t         mag_y;          ///< magnetic field strength along the Y axis
	int16_t         mag_z;          ///< magnetic field strength along the Z axis
	float           heading;        ///< compass heading in radians
	float           heading_x;      ///< compass vector X magnitude
	float           heading_y;      ///< compass vector Y magnitude
	uint32_t        last_update;    ///< millis() time of last update
	bool			healthy;        ///< true if last read OK

	/// Constructor
	///
	Compass();

	/// Initialize the compass device.
	///
	/// @returns    True if the compass was initialized OK, false if it was not
	///             found or is not functioning.
	///
	virtual bool init();
	
	/// Read the compass and update the mag_ variables.
	///
	virtual bool read(void) = 0;

	/// Calculate the tilt-compensated heading_ variables.
	///
	/// @param  roll                The current airframe roll angle.
	/// @param  pitch               The current airframe pitch angle.
	///
	virtual void calculate(float roll, float pitch);

	/// Calculate the tilt-compensated heading_ variables.
	///
	/// @param dcm_matrix			The current orientation rotation matrix
	///
	virtual void calculate(const Matrix3f &dcm_matrix);

	/// Set the compass orientation matrix, used to correct for
	/// various compass mounting positions.
	///
	/// @param  rotation_matrix     Rotation matrix to transform magnetometer readings
	///                             to the body frame.
	///
	virtual void set_orientation(enum Rotation rotation);

	/// Sets the compass offset x/y/z values.
	///
	/// @param  offsets             Offsets to the raw mag_ values.
	///
	virtual void set_offsets(const Vector3f &offsets);

	/// Saves the current compass offset x/y/z values.
	///
	/// This should be invoked periodically to save the offset values maintained by
	/// ::null_offsets.
	///
	virtual void save_offsets();

	/// Returns the current offset values
	///
	/// @returns                    The current compass offsets.
	///
	virtual Vector3f &get_offsets();

	/// Sets the initial location used to get declination - Returns true if declination set
	///
	/// @param  latitude             GPS Latitude.
	/// @param  longitude            GPS Longitude.
	/// @param  force				 Force the compass declination update.
	///
	bool set_initial_location(long latitude, long longitude, bool force);

	/// Program new offset values.
	///
	/// @param  x                   Offset to the raw mag_x value.
	/// @param  y                   Offset to the raw mag_y value.
	/// @param  z                   Offset to the raw mag_z value.
	///
	void set_offsets(int x, int y, int z) { set_offsets(Vector3f(x, y, z)); }

	/// Perform automatic offset updates
	///
	void null_offsets(void);


	/// Enable/Start automatic offset updates 
	///
	void null_offsets_enable(void);


	/// Disable/Stop automatic offset updates
	///
	void null_offsets_disable(void);

    /// return true if the compass should be used for yaw calculations
    bool use_for_yaw(void) { return healthy && _use_for_yaw; }

	/// Sets the local magnetic field declination.
	///
	/// @param  radians             Local field declination.
	///
	virtual void set_declination(float radians);
	float get_declination();

    static const struct AP_Param::GroupInfo var_info[];

protected:
    enum Rotation		_orientation;
	AP_Vector3f         _offset;
	AP_Float            _declination;
    AP_Int8             _learn;                 ///<enable calibration learning
    AP_Int8             _use_for_yaw;           ///<enable use for yaw calculation

	bool                _null_enable;        	///< enabled flag for offset nulling
	bool                _null_init_done;        ///< first-time-around flag used by offset nulling

    ///< used by offset correction
    static const uint8_t _mag_history_size = 20;
    uint8_t				_mag_history_index;
	Vector3i            _mag_history[_mag_history_size];
};
#endif