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.