AP_SpdHgtControl: added speed/height control interface

this will be used by TECS

libraries/AP_SpdHgtControl/AP_SpdHgtControl.h

@@ -0,0 +1,70 @@
+// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
+
+/// @file    AP_SpdHgtControl.h
+/// @brief   generic speed & height controller interface
+
+/*
+  This defines a generic interface for speed & height controllers. Each
+  specific controller should be a subclass of this generic
+  interface. All variables used by controllers should be in their
+  own class.
+ */
+
+#ifndef AP_SPDHGTCONTROL_H
+#define AP_SPDHGTCONTROL_H
+
+#include <AP_Common.h>
+#include <AP_Param.h>
+#include <DataFlash.h>
+
+class AP_SpdHgtControl {
+public:
+	/*
+	  these are key speed/height control parameters which are passed 
+	  to the controller at initialisation
+	 */
+	struct AircraftParameters {
+		AP_Int8 throttle_min;
+		AP_Int8 throttle_max;	
+		AP_Int8 throttle_slewrate;
+		AP_Int8 throttle_cruise;
+		AP_Int16 flybywire_airspeed_min;
+		AP_Int16 flybywire_airspeed_max;
+		AP_Int16 pitch_limit_max_cd;
+		AP_Int16 pitch_limit_min_cd;
+	};
+
+	// Update the internal state of the height and height rate estimator
+	// Update of the inertial speed rate estimate internal state
+	// Should be called at 50Hz or faster
+	virtual void update_50hz(void) = 0;
+
+	// Update of the pitch and throttle demands
+	// Should be called at 10Hz or faster
+	virtual void update_pitch_throttle(int32_t hgt_dem_cm, int32_t EAS_dem_cm, bool climbOutDem, int32_t ptchMinCO_cd) = 0;
+
+	// demanded throttle in percentage
+	// should return 0 to 100
+	virtual int32_t get_throttle_demand(void)=0;
+	
+	// demanded pitch angle in centi-degrees
+	// should return -9000 to +9000
+	virtual int32_t get_pitch_demand(void)=0;
+	
+	// Rate of change of velocity along X body axis in m/s^2
+    virtual float get_VXdot(void)=0;
+	
+	// log data on internal state of the controller. Called at 10Hz
+	virtual void log_data(DataFlash_Class &dataflash, uint8_t msgid) = 0;
+
+	// add new controllers to this enum. Users can then
+	// select which controller to use by setting the
+	// SPDHGT_CONTROLLER parameter
+	enum ControllerType {
+		CONTROLLER_TECS     = 1
+	};
+
+};
+
+
+#endif // AP_SPDHGTCONTROL_H