SITL: added SIM_BARO_DISABLE parameter

useful for testing baro failure

libraries/AP_HAL_AVR_SITL/sitl_barometer.cpp

@@ -38,6 +38,11 @@ void SITL_State::_update_barometer(float altitude)
 		return;
 	}
 
+        if (_sitl->baro_disable) {
+            // barometer is disabled
+            return;
+        }
+
 	// 80Hz, to match the real APM2 barometer
         uint32_t now = hal.scheduler->millis();
 	if ((now - last_update) < 12) {

libraries/SITL/SITL.cpp

@@ -55,6 +55,7 @@ const AP_Param::GroupInfo SITL::var_info[] PROGMEM = {
     AP_GROUPINFO("SONAR_RND",     24, SITL,  sonar_noise, 0),
     AP_GROUPINFO("RC_FAIL",       25, SITL,  rc_fail, 0),
     AP_GROUPINFO("GPS2_ENABLE",   26, SITL,  gps2_enable, 0),
+    AP_GROUPINFO("BARO_DISABLE",  27, SITL,  baro_disable, 0),
     AP_GROUPEND
 };
 

libraries/SITL/SITL.h

@@ -75,6 +75,7 @@ public:
     AP_Float batt_voltage; // battery voltage base
     AP_Float accel_fail;  // accelerometer failure value
 	AP_Int8  rc_fail;     // fail RC input
+	AP_Int8  baro_disable; // disable simulated barometer
 
     // wind control
     AP_Float wind_speed;