Tracker: add support for 4th mavlink channel

AntennaTracker/Parameters.h

@@ -92,6 +92,7 @@ public:
         k_param_pitch_range,
         k_param_distance_min,
         k_param_sysid_target,       // 138
+        k_param_gcs3,               // stream rates for fourth MAVLink port
 
         //
         // 150: Telemetry control

AntennaTracker/Parameters.pde

@@ -222,6 +222,12 @@ const AP_Param::Info var_info[] PROGMEM = {
     GOBJECTN(gcs[2],  gcs2,       "SR2_",     GCS_MAVLINK),
 #endif
 
+#if MAVLINK_COMM_NUM_BUFFERS > 3
+    // @Group: SR3_
+    // @Path: GCS_Mavlink.pde
+    GOBJECTN(gcs[3],  gcs3,       "SR3_",     GCS_MAVLINK),
+#endif
+
     // @Group: INS_
     // @Path: ../libraries/AP_InertialSensor/AP_InertialSensor.cpp
     GOBJECT(ins,                    "INS_", AP_InertialSensor),

AntennaTracker/system.pde

@@ -46,6 +46,12 @@ static void init_tracker()
     gcs[2].set_snoop(mavlink_snoop);
 #endif
 
+#if MAVLINK_COMM_NUM_BUFFERS > 3
+    // setup serial port for fourth telemetry port (not used by default) and start snooping for vehicle data
+    gcs[3].setup_uart(serial_manager, AP_SerialManager::SerialProtocol_MAVLink, 2);
+    gcs[3].set_snoop(mavlink_snoop);
+#endif
+
     mavlink_system.sysid = g.sysid_this_mav;
 
     if (g.compass_enabled==true) {