AP_HAL_SITL: created ADS-B simulator to generate additional ghost aircraft within SITL

- The values are very aggressive, you'll come into contact with another aircraft very soon
- Credit goes to Tridge for this work
- This also allows hardware attached via UART to feed real aircraft into the simulator

This feature is enabled with the following command:
sim_vehicle -A --adsb

libraries/AP_HAL_SITL/SITL_State.cpp

@@ -60,7 +60,7 @@ void SITL_State::_set_param_default(const char *parm)
 /*
   setup for SITL handling
  */
-void SITL_State::_sitl_setup(void)
+void SITL_State::_sitl_setup(const char *home_str)
 {
 #ifndef __CYGWIN__
     _parent_pid = getppid();
@@ -93,6 +93,9 @@ void SITL_State::_sitl_setup(void)
         if (enable_gimbal) {
             gimbal = new Gimbal(_sitl->state);
         }
+        if (enable_ADSB) {
+            adsb = new ADSB(_sitl->state, home_str);
+        }
     }
 
     if (_synthetic_clock_mode) {
@@ -252,6 +255,9 @@ void SITL_State::_fdm_input_local(void)
     if (gimbal != NULL) {
         gimbal->update();
     }
+    if (adsb != NULL) {
+        adsb->update();
+    }
 
     // update simulation time
     hal.scheduler->stop_clock(_sitl->state.timestamp_us);

libraries/AP_HAL_SITL/SITL_State.h

@@ -23,6 +23,7 @@
 #include <AP_Terrain/AP_Terrain.h>
 #include <SITL/SITL.h>
 #include <SITL/SIM_Gimbal.h>
+#include <SITL/SIM_ADSB.h>
 
 class HAL_SITL;
 
@@ -71,7 +72,7 @@ private:
     void _parse_command_line(int argc, char * const argv[]);
     void _set_param_default(const char *parm);
     void _usage(void);
-    void _sitl_setup(void);
+    void _sitl_setup(const char *home_str);
     void _setup_fdm(void);
     void _setup_timer(void);
     void _setup_adc(void);
@@ -200,6 +201,10 @@ private:
     bool enable_gimbal;
     SITL::Gimbal *gimbal;
 
+    // simulated gimbal
+    bool enable_ADSB;
+    SITL::ADSB *adsb;
+    
     // TCP address to connect uartC to
     const char *_client_address;
 };

libraries/AP_HAL_SITL/SITL_cmdline.cpp

@@ -46,6 +46,7 @@ void SITL_State::_usage(void)
            "\t--instance N       set instance of SITL (adds 10*instance to all port numbers)\n"
            "\t--speedup SPEEDUP  set simulation speedup\n"
            "\t--gimbal           enable simulated MAVLink gimbal\n"
+           "\t--adsb             enable simulated ADSB peripheral\n"
            "\t--autotest-dir DIR set directory for additional files\n"
            "\t--uartA device     set device string for UARTA\n"
            "\t--uartB device     set device string for UARTB\n"
@@ -113,7 +114,8 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
         CMDLINE_UARTB,
         CMDLINE_UARTC,
         CMDLINE_UARTD,
-        CMDLINE_UARTE
+        CMDLINE_UARTE,
+        CMDLINE_ADSB,
     };
 
     const struct GetOptLong::option options[] = {
@@ -134,6 +136,7 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
         {"uartE",           true,   0, CMDLINE_UARTE},
         {"client",          true,   0, CMDLINE_CLIENT},
         {"gimbal",          false,  0, CMDLINE_GIMBAL},
+        {"adsb",            false,  0, CMDLINE_ADSB},
         {"autotest-dir",    true,   0, CMDLINE_AUTOTESTDIR},
         {0, false, 0, 0}
     };
@@ -184,6 +187,9 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
         case CMDLINE_GIMBAL:
             enable_gimbal = true;
             break;
+        case CMDLINE_ADSB:
+            enable_ADSB = true;
+            break;
         case CMDLINE_AUTOTESTDIR:
             autotest_dir = strdup(gopt.optarg);
             break;
@@ -240,7 +246,7 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
         }
     }
 
-    _sitl_setup();
+    _sitl_setup(home_str);
 }
 
 #endif