Keep track of USB direct connection links

src/comm/LinkManager.cc

@@ -508,11 +508,13 @@ void LinkManager::_updateAutoConnectLinks(void)
                 case QGCSerialPortInfo::BoardTypePX4FMUV4:
                     if (_autoconnectPixhawk) {
                         pSerialConfig = new SerialConfiguration(QString("Pixhawk on %1").arg(portInfo.portName().trimmed()));
+                        pSerialConfig->setUsbDirect(true);
                     }
                     break;
                 case QGCSerialPortInfo::BoardTypeAeroCore:
                     if (_autoconnectPixhawk) {
                         pSerialConfig = new SerialConfiguration(QString("AeroCore on %1").arg(portInfo.portName().trimmed()));
+                        pSerialConfig->setUsbDirect(true);
                     }
                     break;
                 case QGCSerialPortInfo::BoardTypePX4Flow:

src/comm/SerialLink.cc

@@ -388,6 +388,7 @@ SerialConfiguration::SerialConfiguration(const QString& name) : LinkConfiguratio
     _parity     = QSerialPort::NoParity;
     _dataBits   = 8;
     _stopBits   = 1;
+    _usbDirect  = false;
 }
 
 SerialConfiguration::SerialConfiguration(SerialConfiguration* copy) : LinkConfiguration(copy)
@@ -399,6 +400,7 @@ SerialConfiguration::SerialConfiguration(SerialConfiguration* copy) : LinkConfig
     _stopBits           = copy->stopBits();
     _portName           = copy->portName();
     _portDisplayName    = copy->portDisplayName();
+    _usbDirect          = copy->_usbDirect;
 }
 
 void SerialConfiguration::copyFrom(LinkConfiguration *source)
@@ -413,6 +415,7 @@ void SerialConfiguration::copyFrom(LinkConfiguration *source)
     _stopBits           = ssource->stopBits();
     _portName           = ssource->portName();
     _portDisplayName    = ssource->portDisplayName();
+    _usbDirect          = ssource->_usbDirect;
 }
 
 void SerialConfiguration::updateSettings()
@@ -554,3 +557,10 @@ void SerialConfiguration::_initBaudRates()
     kSupportedBaudRates << "921600";
 }
 
+void SerialConfiguration::setUsbDirect(bool usbDirect)
+{
+    if (_usbDirect != usbDirect) {
+        _usbDirect = usbDirect;
+        emit usbDirectChanged(_usbDirect);
+    }
+}

src/comm/SerialLink.h

@@ -73,12 +73,14 @@ public:
     Q_PROPERTY(int      parity          READ parity             WRITE setParity             NOTIFY parityChanged)
     Q_PROPERTY(QString  portName        READ portName           WRITE setPortName           NOTIFY portNameChanged)
     Q_PROPERTY(QString  portDisplayName READ portDisplayName                                NOTIFY portDisplayNameChanged)
+    Q_PROPERTY(bool     usbDirect       READ usbDirect          WRITE setUsbDirect          NOTIFY usbDirectChanged)        ///< true: direct usb connection to board
 
     int  baud()         { return _baud; }
     int  dataBits()     { return _dataBits; }
     int  flowControl()  { return _flowControl; }    ///< QSerialPort Enums
     int  stopBits()     { return _stopBits; }
     int  parity()       { return _parity; }         ///< QSerialPort Enums
+    bool usbDirect()    { return _usbDirect; }
 
     const QString portName          () { return _portName; }
     const QString portDisplayName   () { return _portDisplayName; }
@@ -89,6 +91,7 @@ public:
     void setStopBits        (int stopBits);
     void setParity          (int parity);               ///< QSerialPort Enums
     void setPortName        (const QString& portName);
+    void setUsbDirect       (bool usbDirect);
 
     static QStringList supportedBaudRates();
     static QString cleanPortDisplayname(const QString name);
@@ -109,6 +112,7 @@ signals:
     void parityChanged          ();
     void portNameChanged        ();
     void portDisplayNameChanged ();
+    void usbDirectChanged       (bool usbDirect);
 
 private:
     static void _initBaudRates();
@@ -121,6 +125,7 @@ private:
     int _parity;
     QString _portName;
     QString _portDisplayName;
+    bool _usbDirect;
 };
 
 /**