How can I detect usb removed when serial port is open?

TheCeylann

There is a datalogger that measures temperature and humidity. I am reading the recorded temperature and humidity data using QSerialPort. I want to terminate the serial port connection if the usb is removed from my computer while my Serial Port is open. How can I detect that the USB has been removed? I would be glad if you help me in this regard..

Paul Colby

Hi @TheCeylann,

Seems like you want to watch for QSerialPort::ResourceError errors (among others):

QSerialPort::ResourceError An I/O error occurred when a resource becomes unavailable, e.g. when the device is unexpectedly removed from the system.

So perhaps something like:

connect(&serialPort, &QSerialPort::errorOccurred, this, [](const QSerialPort::SerialPortError error) {
  if (error == QSerialPort::ResourceError) {
    // handle possible unplugged event.
  }
});

Cheers.

kuzulis

The ResourceError may trigger or may not trigger, it depends on the OS, on the driver type and version.

A best way is to write an own class watcher based on the SetupAPI on Windows, or the Udev on Linux, (but the MacOSX has something similar, I think), which will subscribe to the detach events for the desired device class (USB or SEIRIAL). You can use a GOOGLE to search how to use that APIs.

SGaist

Hi,

Another possibility is to use KDE's Solid framework. It is cross-platform and should allow you to implement what @kuzulis suggests without going low level.