README.md
Sensors

All the base classes are inherited from the Sensor class, which is a virtual class and cannot be used as-is. Sensor class also contains static variables and functions to access the available sensors (manually configured / detected at runtime).

As many as requested sensors can be used ( within the limits of how many sensors the I2C/SPI/other busses support ). Attitude sensors and GPSs are mixed together (by IMU::UpdateSensors()) if several of them are used.

Any axis of each sensors can be swapped ( or the whole vector can be multiplied by a matrix ) to allow easier alignement between the sensor and drone's frame. ( see Sensor::setAxisSwap() and Sensor::setAxisMatrix(), used in LUA configuration as axis_swap ). Applying the swap must be implemented in each sensor driver inside the Read function.

Adding new device driver

New sensor drivers must inherit from one of the following classes :
 * Gyroscope
 * Accelerometer
 * ~~Magnetometer~~ ( Not used yet )
 * ~~Altimeter~~ ( WIP )
 * ~~GPS~~ ( Not used yet )
 * Voltmeter
 * CurrentSensor

Gyroscopes, accelerometers and magnetometers

These sensors are used for attitude computation. Each attitude sensor must return a 3-axis vector from its ::Read() function, if the sensor has only 1 or 2 axes, it must fill the relevant parts of the returned 3-axis vector and put the others to 0.

The following virtual members must be implemented :
 * virtual void Calibrate( float dt, bool last_pass = false )Called several times (a few hundred times) on automatic/manual sensors calibration, dt is the the time in seconds since the last call to this function, last_pass is set to true when this function is called for the last time. The function can be let empty if no calibration is needed.
 * virtual void Read( Vector3f* v, bool raw = false );Called every time the IMU needs new attitude data, current values must be swapped using axis_swap if set and finally put to v. If raw is true, calibration offsets must be ignored and data returned as-is after axis-swap.

The following virtual members can be implemented :
 * virtual string infos()Returns a string containing sensor informations (manufacturer, model, bus type and speed, etc)

Voltmeter

Required members :
 * virtual void Calibrate( float dt, bool last_pass = false )Same as above
 * virtual float Read( int channel = 0 )Must return current measured voltage on specified channel

Optional members :
 * virtual string infos()Same as above

GPS

Required members :
 * virtual void Calibrate( float dt, bool last_pass = false )Same as above
 * virtual bool Read( float* latitude, float* longitude, float* altitude, float* speed )Must set latitude, longitude, altitude and speed with current GPS data and return true if current position is known, otherwise return false.
 * virtual time_t getTime()Must return current time in seconds since Epoch if known from GPS module, otherwise return 0.

Optional members :
 * virtual string infos()Same as above