AP_OpticalFlow: add singleton

libraries/AP_OpticalFlow/OpticalFlow.cpp

@@ -73,6 +73,8 @@ OpticalFlow::OpticalFlow(AP_AHRS_NavEKF &ahrs)
     : _ahrs(ahrs),
       _last_update_ms(0)
 {
+    _singleton = this;
+
     AP_Param::setup_object_defaults(this, var_info);
 }
 
@@ -124,3 +126,14 @@ void OpticalFlow::update(void)
     _flags.healthy = (AP_HAL::millis() - _last_update_ms < 500);
 }
 
+// singleton instance
+OpticalFlow *OpticalFlow::_singleton;
+
+namespace AP {
+
+OpticalFlow *opticalflow()
+{
+    return OpticalFlow::get_singleton();
+}
+
+}

libraries/AP_OpticalFlow/OpticalFlow.h

@@ -36,6 +36,11 @@ public:
     OpticalFlow(const OpticalFlow &other) = delete;
     OpticalFlow &operator=(const OpticalFlow&) = delete;
 
+    // get singleton instance
+    static OpticalFlow *get_singleton() {
+        return _singleton;
+    }
+
     // init - initialise sensor
     void init(void);
 
@@ -79,6 +84,9 @@ public:
     static const struct AP_Param::GroupInfo var_info[];
 
 private:
+
+    static OpticalFlow *_singleton;
+
     AP_AHRS_NavEKF &_ahrs;
     OpticalFlow_backend *backend;
 
@@ -100,4 +108,8 @@ private:
     uint32_t _last_update_ms;        // millis() time of last update
 };
 
+namespace AP {
+    OpticalFlow *opticalflow();
+}
+
 #include "OpticalFlow_backend.h"