CODEWITHSUNDEEP
qtvirtual-serial-port
honestapple
honestapple

Reputation: 11

Do I need multithread?

I am developping a project about data sampling and realtime display like oscilloscope. The data are transfered to PC with virtual com port at a high trandfer rate. I am using QT4.8.4 + Qextserialport to accomplish serial port communication on WindowsXP.

I have tested the device using AccessPort. It could receive the data from the port, but have no response to write to it. If I wanted to make the device stop uploading data, I must stop the device and write stop command to it, restarted the device, then the device stopped uploading. It is the same for the application using one thread to process reading and writing. I did not want to close the port completely. I just wanted to enter some command to change something, the sampling rate, the data format, etc.

So, I tried multithread. I downloaded a reference code from the following link. http://www.qtcentre.org/threads/21063-QextSerialPort-with-QTimer-approch-for-reading?p=103325&highlight=#post103325 (I am sorry, I really do not know how to paste code fitly on this site)

In this code, the author derived two subclass of QThread. One is for reading port, the other is for writing port. He also reimplemented the run() in these two subclass. I tried this code, but found that when receiving code, my GUI frozen.

It seem that the author in the following thread met the same question with me. Qt: GUI sometimes freezing when using threads and signals/slots

But I have question about this thread.

  1. The author mentioned "When running the code in the GUI-thread, there is no problem."

Did the author mean that everything is OK when the all code in GUI-thread? So, why he used worker thread and process thread?

  1. The author mentioned "Process thread"

Do I need a another process thread to work with GUI thread which is responsible for display?(I need to display not only the data but also the waveform, all must in realtime)

Please give me some tips on how to conquer this problem. Thanks a lot.

Upvotes: 0

Views: 194

Answers (1)

john.pavan
john.pavan

Reputation: 950

The short answer is yes. Doing any heavy processing on a GUI thread will result in freezing the GUI (esp if you block). Instead you should either have an independent thread that updates the data, or spin off worker threads for specific tasks. In either case, when there is new data to display you should signal the GUI thread when there is new data to display. If possible, I'd recommend using the MVC pattern and implement a QAbstractItemModel to provide data to your view (as it has a defined pattern for providing those updates).

Upvotes: 0

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