AP_Beacon: add singleton

libraries/AP_Beacon/AP_Beacon.cpp

@@ -75,6 +75,12 @@ const AP_Param::GroupInfo AP_Beacon::var_info[] = {
 AP_Beacon::AP_Beacon(AP_SerialManager &_serial_manager) :
     serial_manager(_serial_manager)
 {
+#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
+    if (_singleton != nullptr) {
+        AP_HAL::panic("Fence must be singleton");
+    }
+#endif
+    _singleton = this;
     AP_Param::setup_object_defaults(this, var_info);
 }
 
@@ -376,3 +382,16 @@ bool AP_Beacon::device_ready(void) const
 {
     return ((_driver != nullptr) && (_type != AP_BeaconType_None));
 }
+
+
+// singleton instance
+AP_Beacon *AP_Beacon::_singleton;
+
+namespace AP {
+
+AP_Beacon *beacon()
+{
+    return AP_Beacon::get_singleton();
+}
+
+}

libraries/AP_Beacon/AP_Beacon.h

@@ -34,6 +34,9 @@ public:
 
     AP_Beacon(AP_SerialManager &_serial_manager);
 
+    // get singleton instance
+    static AP_Beacon *get_singleton() { return _singleton; }
+
     // external position backend types (used by _TYPE parameter)
     enum AP_BeaconType {
         AP_BeaconType_None   = 0,
@@ -102,6 +105,8 @@ public:
 
 private:
 
+    static AP_Beacon *_singleton;
+
     // check if device is ready
     bool device_ready(void) const;
 
@@ -138,3 +143,7 @@ private:
     uint8_t boundary_num_points;                // number of points in boundary
     uint8_t boundary_num_beacons;               // total number of beacon points consumed while building boundary
 };
+
+namespace AP {
+    AP_Beacon *beacon();
+};