AP_InertialSensor: make get_delta_time() const

allows use from AP_NavEKF

libraries/AP_InertialSensor/AP_InertialSensor.h

@@ -135,7 +135,7 @@ public:
     /* get_delta_time returns the time period in seconds
      * overwhich the sensor data was collected
      */
-    virtual float get_delta_time() = 0;
+    virtual float get_delta_time() const = 0;
 
     // return the maximum gyro drift rate in radians/s/s. This
     // depends on what gyro chips are being used

libraries/AP_InertialSensor/AP_InertialSensor_Flymaple.cpp

@@ -224,7 +224,7 @@ bool AP_InertialSensor_Flymaple::update(void)
     return true;
 }
 
-float AP_InertialSensor_Flymaple::get_delta_time(void) 
+float AP_InertialSensor_Flymaple::get_delta_time(void) const
 {
     return _delta_time;
 }

libraries/AP_InertialSensor/AP_InertialSensor_Flymaple.h

@@ -19,7 +19,7 @@ public:
 
     /* Concrete implementation of AP_InertialSensor functions: */
     bool            update();
-    float        	get_delta_time();
+    float        	get_delta_time() const;
     float           get_gyro_drift_rate();
     bool            wait_for_sample(uint16_t timeout_ms);
 

libraries/AP_InertialSensor/AP_InertialSensor_HIL.cpp

@@ -32,7 +32,7 @@ bool AP_InertialSensor_HIL::update( void ) {
     return true;
 }
 
-float AP_InertialSensor_HIL::get_delta_time() {
+float AP_InertialSensor_HIL::get_delta_time() const {
     return _delta_time_usec * 1.0e-6;
 }
 

libraries/AP_InertialSensor/AP_InertialSensor_HIL.h

@@ -14,7 +14,7 @@ public:
 
     /* Concrete implementation of AP_InertialSensor functions: */
     bool            update();
-    float	        get_delta_time();
+    float	        get_delta_time() const;
     float           get_gyro_drift_rate();
     bool            wait_for_sample(uint16_t timeout_ms);
     void            set_accel(const Vector3f &accel);

libraries/AP_InertialSensor/AP_InertialSensor_L3G4200D.cpp

@@ -270,7 +270,7 @@ bool AP_InertialSensor_L3G4200D::update(void)
     return true;
 }
 
-float AP_InertialSensor_L3G4200D::get_delta_time(void) 
+float AP_InertialSensor_L3G4200D::get_delta_time(void) const
 {
     return _sample_period_usec * 1.0e-6f;
 }

libraries/AP_InertialSensor/AP_InertialSensor_L3G4200D.h

@@ -19,7 +19,7 @@ public:
 
     /* Concrete implementation of AP_InertialSensor functions: */
     bool            update();
-    float        	get_delta_time();
+    float        	get_delta_time() const;
     float           get_gyro_drift_rate();
     bool            wait_for_sample(uint16_t timeout_ms);
 

libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp

@@ -588,7 +588,7 @@ void AP_InertialSensor_MPU6000::_dump_registers(void)
 
 
 // get_delta_time returns the time period in seconds overwhich the sensor data was collected
-float AP_InertialSensor_MPU6000::get_delta_time() 
+float AP_InertialSensor_MPU6000::get_delta_time() const
 {
     // the sensor runs at 200Hz
     return 0.005 * _num_samples;

libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h

@@ -28,7 +28,7 @@ public:
     bool                wait_for_sample(uint16_t timeout_ms);
 
     // get_delta_time returns the time period in seconds overwhich the sensor data was collected
-    float            	get_delta_time();
+    float            	get_delta_time() const;
 
     uint16_t error_count(void) const { return _error_count; }
     bool healthy(void) const { return _error_count <= 4; }

libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.cpp

@@ -112,7 +112,7 @@ bool AP_InertialSensor_Oilpan::update()
     return true;
 }
 
-float AP_InertialSensor_Oilpan::get_delta_time() {
+float AP_InertialSensor_Oilpan::get_delta_time() const {
     return _delta_time_micros * 1.0e-6;
 }
 

libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.h

@@ -17,7 +17,7 @@ public:
 
     /* Concrete implementation of AP_InertialSensor functions: */
     bool            update();
-    float        	get_delta_time();    // get_delta_time returns the time period in seconds overwhich the sensor data was collected    
+    float        	get_delta_time() const;
     float           get_gyro_drift_rate();
 
     // wait for a sample to be available, with timeout in milliseconds

libraries/AP_InertialSensor/AP_InertialSensor_PX4.cpp

@@ -171,7 +171,7 @@ bool AP_InertialSensor_PX4::update(void)
     return true;
 }
 
-float AP_InertialSensor_PX4::get_delta_time(void)
+float AP_InertialSensor_PX4::get_delta_time(void) const
 {
     return _sample_time_usec * 1.0e-6f;
 }

libraries/AP_InertialSensor/AP_InertialSensor_PX4.h

@@ -26,7 +26,7 @@ public:
 
     /* Concrete implementation of AP_InertialSensor functions: */
     bool            update();
-    float        	get_delta_time();
+    float        	get_delta_time() const;
     float           get_gyro_drift_rate();
     bool            wait_for_sample(uint16_t timeout_ms);
     bool            healthy(void) const;