AP_RSSI: add singleton

libraries/AP_RSSI/AP_RSSI.cpp

@@ -97,6 +97,10 @@ const AP_Param::GroupInfo AP_RSSI::var_info[] = {
 AP_RSSI::AP_RSSI()
 {       
     AP_Param::setup_object_defaults(this, var_info);
+    if (_s_instance) {
+        AP_HAL::panic("Too many RSSI sensors");
+    }
+    _s_instance = this;
 }
 
 // destructor
@@ -104,6 +108,14 @@ AP_RSSI::~AP_RSSI(void)
 {       
 }
 
+/*
+ * Get the AP_RSSI singleton
+ */
+AP_RSSI *AP_RSSI::get_instance()
+{
+    return _s_instance;
+}
+
 // Initialize the rssi object and prepare it for use
 void AP_RSSI::init()
 {
@@ -200,3 +212,14 @@ float AP_RSSI::scale_and_constrain_float_rssi(float current_rssi_value, float lo
     // value retrieved falls outside the user-supplied range.
     return constrain_float(rssi_value_scaled, 0.0f, 1.0f);
 }
+
+AP_RSSI *AP_RSSI::_s_instance = nullptr;
+
+namespace AP {
+
+AP_RSSI *rssi()
+{
+    return AP_RSSI::get_instance();
+}
+
+};

libraries/AP_RSSI/AP_RSSI.h

@@ -37,6 +37,8 @@ public:
     // destructor
     ~AP_RSSI(void);
 
+    static AP_RSSI *get_instance();
+
     // Initialize the rssi object and prepare it for use
     void init();
 
@@ -55,6 +57,9 @@ public:
     static const struct AP_Param::GroupInfo var_info[];
 
 private:
+
+    static AP_RSSI *_s_instance;
+
     // RSSI parameters
     AP_Int8         rssi_type;                              // Type of RSSI being used
     AP_Int8         rssi_analog_pin;                        // Analog pin RSSI value found on
@@ -77,3 +82,7 @@ private:
     // Scale and constrain a float rssi value to 0.0 to 1.0 range 
     float scale_and_constrain_float_rssi(float current_rssi_value, float low_rssi_range, float high_rssi_range);
 };
+
+namespace AP {
+    AP_RSSI *rssi();
+};