Only consider the port to be open if a serial number can be read within 500 milliseconds.

protocol/enttec/dmx-usb-pro/widget.cpp

@@ -86,8 +86,11 @@ void Widget::halt()
  */
 void Widget::open()
 {
-  std::scoped_lock lock(mtx_metadata_);
-  usb_mode_ = USBhost;
+  if (getSerialNumber(500))                 // check for valid call/response from device
+  {
+      std::scoped_lock lock(mtx_metadata_);
+      usb_mode_ = USBhost;                   // note connected state
+  }
 }