AP_RangeFinder: correct MAVLink backend's out-of-range checks

libraries/AP_RangeFinder/AP_RangeFinder_Backend.cpp

@@ -56,9 +56,9 @@ bool AP_RangeFinder_Backend::has_data() const {
 void AP_RangeFinder_Backend::update_status()
 {
     // check distance
-    if ((int16_t)state.distance_cm > params.max_distance_cm) {
+    if ((int16_t)state.distance_cm > max_distance_cm()) {
         set_status(RangeFinder::Status::OutOfRangeHigh);
-    } else if ((int16_t)state.distance_cm < params.min_distance_cm) {
+    } else if ((int16_t)state.distance_cm < min_distance_cm()) {
         set_status(RangeFinder::Status::OutOfRangeLow);
     } else {
         set_status(RangeFinder::Status::Good);

libraries/AP_RangeFinder/AP_RangeFinder_Backend.h

@@ -39,8 +39,8 @@ public:
     enum Rotation orientation() const { return (Rotation)params.orientation.get(); }
     uint16_t distance_cm() const { return state.distance_cm; }
     uint16_t voltage_mv() const { return state.voltage_mv; }
-    int16_t max_distance_cm() const { return params.max_distance_cm; }
-    int16_t min_distance_cm() const { return params.min_distance_cm; }
+    virtual int16_t max_distance_cm() const { return params.max_distance_cm; }
+    virtual int16_t min_distance_cm() const { return params.min_distance_cm; }
     int16_t ground_clearance_cm() const { return params.ground_clearance_cm; }
     MAV_DISTANCE_SENSOR get_mav_distance_sensor_type() const;
     RangeFinder::Status status() const;

libraries/AP_RangeFinder/AP_RangeFinder_MAVLink.cpp

@@ -28,6 +28,8 @@ void AP_RangeFinder_MAVLink::handle_msg(const mavlink_message_t &msg)
     if (packet.orientation == MAV_SENSOR_ROTATION_PITCH_270) {
         state.last_reading_ms = AP_HAL::millis();
         distance_cm = packet.current_distance;
+        _max_distance_cm = packet.max_distance;
+        _min_distance_cm = packet.min_distance;
         sensor_type = (MAV_DISTANCE_SENSOR)packet.type;
     }
 }

libraries/AP_RangeFinder/AP_RangeFinder_MAVLink.h

@@ -23,6 +23,9 @@ public:
     // Get update from mavlink
     void handle_msg(const mavlink_message_t &msg) override;
 
+    int16_t max_distance_cm() const override { return _max_distance_cm; }
+    int16_t min_distance_cm() const override { return _min_distance_cm; }
+
 protected:
 
     MAV_DISTANCE_SENSOR _get_mav_distance_sensor_type() const override {
@@ -30,7 +33,11 @@ protected:
     }
 
 private:
+
+    // stored data from packet:
     uint16_t distance_cm;
+    uint16_t _max_distance_cm;
+    uint16_t _min_distance_cm;
 
     // start a reading
     static bool start_reading(void);