QtSerialPort and CPU usage

kuzulis

2Dolbyz,

Previously had a similar problem with the CPU load, using the USB / Serial converter chip Prolific. The problem was that in a false fire notifier QWinEventNotifier at data receiving. Presumably the reason is the driver, although it is difficult to say. Previously, I seems to be fixed this problem, though .. I try will check again.

Dolbyz

My colleague found another usb-to-serial cable (USB-SERIAL CH340 wch.cn). It works perfectly.

When I debugged with the old cable it seemed to loop in qevendispatcher_win.cpp:770 for loop. With the old cable I got from two to eight readyRead-signals (message length about 16 bytes). With this "new" cable, just single signal with whole data.

Thanks for your help.

kuzulis

Please try to fix the code in the source code library QtSerialPort to test, as described "here":https://bugreports.qt-project.org/browse/QTPLAYGROUND-2 and take there is an example of an "attached":https://bugreports.qt-project.org/secure/attachment/28890/TestSerial.zip for testing.

Dolbyz

I tried this fix. The problem still occurs. I used my own code for testing.

For second try I put debug print to that event-function. I guess it was called "few" times, because then qt creator jammed too :)

kuzulis

Bad bad bad. I do not have ideas how to fix it.

kuzulis

UPD: Please try repeat test with new test tool "CpuUsageTester":https://bugreports.qt-project.org/secure/attachment/28899/CpuUsageTester.zip

Dolbyz

It works exactly same way with this test application.

kuzulis

Clear, thx

So, most likely a problem in the drivers.

kuzulis

2 Dolbyz,

Please check CPU load with a new concept from "here":https://codereview.qt-project.org/#change,32186

PS: If you have free time.

Dolbyz

I'll try to test during this week.

Dolbyz

With this version I could not reproduce the 100% CPU usage-bug.

At least previously it happened almost immediately. Now I tried for some time, but no issues.