threaded serial port communication in C++ with Qt

Question

I am writing an QT desktop application that is going to display information received from a serial port. Therefore a class was created and packed into an DLL using standard Windows API features to communicate with the connected device (CreateFile, ReadFile, WriteFile, ...).

At the moment a timer calls the DLL at a predefined rate [< 200ms] and this leads the gui to freeze for short periods. Because of that i am thinking of using a thread to do the serial port stuff, that is also going to display everything.

Is is better to use threads for this problem or should i rewrite the class to do the work event based? The target is, that the gui doesnt freeze.

Edit: I solved the problem using a QThread derived worker class with an overshadowed run() function, that handles the serial port communication in the background and updates the gui as new informations are available.

Answer 1

It is good practice in many use cases to do all blocking (synchronous) I/O on a separate thread, especially when a graphical user interface is involved. Here's a page I've referenced regarding the challenges with synchronous I/O (as opposed to asynchronous where your code doesn't block but is still single-threaded, or parallel as you're discussing). There are more issues than just what you brought up, for example:

• What if there is no data available? Does the GUI block until there is data? For example, if the sender was off then there would be no data
• What does the program do if the I/O device is no longer available? For example, if it is a USB-to-serial adapter, what happens if the adapter is unplugged?