AP_AHRS : add method to report if EKF is waiting to start

libraries/AP_AHRS/AP_AHRS.h

@@ -338,6 +338,9 @@ public:
     // is the AHRS subsystem healthy?
     virtual bool healthy(void) = 0;
 
+    // is the EKF waiting to start?
+    virtual bool ekfNotStarted(void) = 0;
+
 protected:
     AHRS_VehicleClass _vehicle_class;
 

libraries/AP_AHRS/AP_AHRS_DCM.cpp

@@ -937,3 +937,8 @@ bool AP_AHRS_DCM::healthy(void)
     // consider ourselves healthy if there have been no failures for 5 seconds
     return (_last_failure_ms == 0 || hal.scheduler->millis() - _last_failure_ms > 5000);
 }
+
+bool AP_AHRS_DCM::ekfNotStarted(void)
+{
+    return false;
+}

libraries/AP_AHRS/AP_AHRS_DCM.h

@@ -106,6 +106,9 @@ public:
     // is the AHRS subsystem healthy?
     bool healthy(void);
 
+    // is the EKF waiting to start?
+    bool ekfNotStarted(void);
+
 private:
     float _ki;
     float _ki_yaw;

libraries/AP_AHRS/AP_AHRS_NavEKF.cpp

@@ -266,5 +266,10 @@ bool AP_AHRS_NavEKF::healthy(void)
     return AP_AHRS_DCM::healthy();    
 }
 
+bool AP_AHRS_NavEKF::ekfNotStarted(void)
+{
+    return !ekf_started;
+}
+
 #endif // AP_AHRS_NAVEKF_AVAILABLE
 

libraries/AP_AHRS/AP_AHRS_NavEKF.h

@@ -95,6 +95,9 @@ public:
     // is the AHRS subsystem healthy?
     bool healthy(void);
 
+    // is the EKF waiting to start?
+    bool ekfNotStarted(void);
+
 private:
     bool using_EKF(void) const;