QtSerialPort and FTDI Driver Issues

[samfallday]

Hello all, I ran across an issue with QtSerialPort library and default terminal example code shown here:

[https://code.qt.io/cgit/qt/qtserialport.git/tree/examples/serialport/terminal?h=6.5](link url)

combined with a serial device using the FTDI D2XX drivers shown here (2.14.1.8):

[https://www.catalog.update.microsoft.com/Search.aspx?q=usb+serial+converter+ftdi+10+](link url)

The problem is some sort of timeout or other issue causing the serial port to not receive data. It works once and only once when I first open the program then never again. Again this is untouched example code (terminal.pro) that is having this issue. I did some troubleshooting and traced the issue to a driver update, the FTDI USB serial cable works with the previous driver (2.12.36.4) but Windows is pushing an update to the new driver (2.14.1.8).

Using several third-party programs however, i.e. Realterm, XCTU, Hercules TCP, etc shows that the data comes through just fine. Apparently the issue is with the QtSerialPort library and the new-ish FTDI driver. Is there some sort of workaround that can be applied or something I could try to overcome this?

FYI:
I've tried compiling the code using both mingw 11.2.0 64-bit and MSVC2019 64-bit using the Qt 6.5.2 framework. Additionally I've tried this using the Qt 5.15.1 framework with the same compile options to no avail.

[SGaist]

Hi and welcome to devnet,

Did you check whether the other applications are using the same parameters as you do ? Maybe something more ?

[samfallday]

@SGaist like the baud rate, parity, data bits? If so I set that the same as I did on the Terminal example. I assume these other 3rd party programs are built on the Windows API and that is what makes the difference.

[Christian Ehrlicher]

@samfallday said in QtSerialPort and FTDI Driver Issues:

I assume these other 3rd party programs are built on the Windows API and that is what makes the difference.

Qt is using the same windows api as other tools - they don't add some magic new functions to Qt. You have to find out what they're doing different to Qt.