AP_IMU: added num_samples_available to allow main loop timing to be synced with arrival of new data from IMU.

libraries/AP_IMU/AP_IMU_INS.cpp

@@ -257,3 +257,9 @@ float AP_IMU_INS::get_gyro_drift_rate(void)
 {
     return _ins->get_gyro_drift_rate();
 }
+
+/// Get number of samples read from the sensors
+uint16_t AP_IMU_INS::num_samples_available(void)
+{
+    return _ins->num_samples_available();
+}

libraries/AP_IMU/AP_IMU_INS.h

@@ -55,6 +55,9 @@ public:
     virtual bool            update(void);
     virtual bool            new_data_available(void);
 
+    /// Get number of samples read from the sensors
+    virtual uint16_t        num_samples_available(void);
+
     // for jason
     virtual float           gx()                            {
         return _sensor_cal[0];
@@ -95,7 +98,6 @@ public:
     }
     virtual float           get_gyro_drift_rate(void);
 
-
 private:
     AP_InertialSensor *         _ins;   ///< INS provides an axis and unit correct sensor source.
 

libraries/AP_IMU/IMU.cpp

@@ -41,6 +41,11 @@ bool IMU::new_data_available(void) {
     return true;
 }
 
+uint16_t IMU::num_samples_available(void)
+{
+    return 0;
+}
+
 float IMU::gx(void) {
     return 0.0;
 }

libraries/AP_IMU/IMU.h

@@ -62,9 +62,18 @@ public:
     ///
     virtual bool        update(void);
 
-    // true if new data is available from the sensors
+    /// Check if new sensor data is available
+    ///
+    /// @returns    true if new data is available from the sensors
+    ///
     virtual bool        new_data_available(void);
 
+    /// Get number of samples read from the sensors
+    ///
+    /// @returns    number of samples read from the sensors
+    ///
+    virtual uint16_t     num_samples_available(void);
+
     /// Fetch the current gyro values
     ///
     /// @returns	vector of rotational rates in radians/sec