ardupilot/libraries/AP_OpticalFlow/AP_OpticalFlow.h

#ifndef AP_OPTICALFLOW_H
#define AP_OPTICALFLOW_H

/*
	AP_OpticalFlow.cpp - OpticalFlow Base Class for Ardupilot Mega
	Code by Randy Mackay. DIYDrones.com

	This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

	Methods:
		init()           : initializate sensor and library.
		read             : reads latest value from OpticalFlow and stores values in x,y, surface_quality parameter
		read_register()  : reads a value from the sensor (will be sensor specific)
		write_register() : writes a value to one of the sensor's register (will be sensor specific)
*/

#include <FastSerial.h>
#include <AP_Math.h>
#include <AP_Common.h>

class AP_OpticalFlow
{
	public:
	int raw_dx, raw_dy;   // raw sensor change in x and y position (i.e. unrotated)
	int surface_quality;  // image quality (below 15 you really can't trust the x,y values returned)
	int x,y;              // total x,y position
	int dx,dy;            // rotated change in x and y position
    float vlon, vlat;       // position as offsets from original position
	unsigned long last_update;    // millis() time of last update
	float field_of_view;  // field of view in Radians
	float scaler;        // number returned from sensor when moved one pixel
	int num_pixels;      // number of pixels of resolution in the sensor
	// temp variables - delete me!
    float exp_change_x, exp_change_y;
    float change_x, change_y;
	float x_cm, y_cm;

	AP_OpticalFlow() { _sensor = this; };
	~AP_OpticalFlow() { _sensor = NULL; };
	virtual bool init(bool initCommAPI = true); // parameter controls whether I2C/SPI interface is initialised (set to false if other devices are on the I2C/SPI bus and have already initialised the interface)
	virtual byte read_register(byte address);
	virtual void write_register(byte address, byte value);
	virtual void set_orientation(enum Rotation rotation); // Rotation vector to transform sensor readings to the body frame.
	virtual void set_field_of_view(const float fov) { field_of_view = fov; update_conversion_factors(); };  // sets field of view of sensor
    static void read(uint32_t ) { if( _sensor != NULL ) _sensor->update(); }; // call to update all attached sensors
    virtual bool update(); // read latest values from sensor and fill in x,y and totals.  returns true on success
	virtual void update_position(float roll, float pitch, float cos_yaw_x, float sin_yaw_y, float altitude);  // updates internal lon and lat with estimation based on optical flow

protected:
    static AP_OpticalFlow *_sensor;  // pointer to the last instantiated optical flow sensor.  Will be turned into a table if we ever add support for more than one sensor
	enum Rotation   _orientation;
	float conv_factor; // multiply this number by altitude and pixel change to get horizontal move (in same units as altitude)
    float radians_to_pixels;
	float _last_roll, _last_pitch, _last_altitude;
	virtual void apply_orientation_matrix();  // rotate raw values to arrive at final x,y,dx and dy values
	virtual void update_conversion_factors();
};

#include "AP_OpticalFlow_ADNS3080.h"

#endif