AP_AHRS: add accessor for GSF yaw estimator

libraries/AP_AHRS/AP_AHRS.cpp

@@ -3132,6 +3132,31 @@ enum Rotation AP_AHRS::get_view_rotation(void) const
     return _view?_view->get_rotation():ROTATION_NONE;
 }
 
+// check if non-compass sensor is providing yaw.  Allows compass pre-arm checks to be bypassed
+const EKFGSF_yaw *AP_AHRS::get_yaw_estimator(void) const
+{
+    switch (active_EKF_type()) {
+#if HAL_NAVEKF2_AVAILABLE
+    case EKFType::TWO:
+        return EKF2.get_yawEstimator();
+#endif
+    case EKFType::NONE:
+#if HAL_NAVEKF3_AVAILABLE
+    case EKFType::THREE:
+        return EKF3.get_yawEstimator();
+#endif
+#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
+    case EKFType::SIM:
+#endif
+#if HAL_EXTERNAL_AHRS_ENABLED
+    case EKFType::EXTERNAL:
+#endif
+        return nullptr;
+    }
+    // since there is no default case above, this is unreachable
+    return nullptr;
+}
+
 // singleton instance
 AP_AHRS *AP_AHRS::_singleton;
 

libraries/AP_AHRS/AP_AHRS.h

@@ -53,6 +53,9 @@ class AP_AHRS_View;
 
 #include <AP_NMEA_Output/AP_NMEA_Output.h>
 
+// fwd declare GSF estimator
+class EKFGSF_yaw;
+
 class AP_AHRS {
     friend class AP_AHRS_View;
 public:
@@ -594,6 +597,9 @@ public:
     // get the view's rotation, or ROTATION_NONE
     enum Rotation get_view_rotation(void) const;
 
+    // get access to an EKFGSF_yaw estimator
+    const EKFGSF_yaw *get_yaw_estimator(void) const;
+
 private:
 
     // optional view class