Sub: Set default external baro bus correctly for Pixhawk 2

ArduSub/Parameters.cpp

@@ -808,7 +808,6 @@ void Sub::load_parameters(void)
     convert_old_parameters();
 
     AP_Param::set_default_by_name("BRD_SAFETYENABLE", 0);
-    AP_Param::set_default_by_name("GND_EXT_BUS", 1);
     AP_Param::set_default_by_name("ARMING_CHECK",
             AP_Arming::ARMING_CHECK_RC |
             AP_Arming::ARMING_CHECK_VOLTAGE |

ArduSub/system.cpp

@@ -35,6 +35,20 @@ void Sub::init_ardupilot()
     BoardConfig_CAN.init();
 #endif
 
+#if CONFIG_HAL_BOARD == HAL_BOARD_PX4
+    // Detection won't work until after BoardConfig.init()
+    switch (AP_BoardConfig::get_board_type()) {
+    case AP_BoardConfig::PX4_BOARD_PIXHAWK2:
+        AP_Param::set_default_by_name("GND_EXT_BUS", 0);
+        break;
+    default:
+        AP_Param::set_default_by_name("GND_EXT_BUS", 1);
+        break;
+    }
+#else
+    AP_Param::set_default_by_name("GND_EXT_BUS", 1);
+#endif
+
     // identify ourselves correctly with the ground station
     mavlink_system.sysid = g.sysid_this_mav;