QSerialPort open error code 10

[addebito]

@kuzulis said in QSerialPort open error code 10:

If this does not work when you did:
...
if (!::GetCommState(handle, &dcb))
{
systemErrorCode = ::GetLastError();
qDebug() << "GetCommState error:" << systemErrorCode << qt_error_string(systemErrorCode);
return;
}
...

and then immediatelly:
...
if (!::SetCommState(handle, &dcb))
{
systemErrorCode = ::GetLastError();
qDebug() << "SetCommState error:" << systemErrorCode << qt_error_string(systemErrorCode);
return;
}
...

Doesn't work. Look tha values on the right side... ?!?

Then you can install the serial port sniffer application and to sniff the device I/O control call for the SetCommStat. To see, which parameters are passed with this call e.g using the hercules application, and to compare with the qtserialport.

Do you know some good sniffer program that you have already used?

Most likelly, it is a bug in FW of your device (in USB CDC class implementation). Or, maybe it expect some specific DCB structure (some specific DCB flags).
Question: Do you have the specific serial port driver for your device, or do you use the 'standard' usbser.sys driver from Windows?

No, I'm using the standard windows usbser.sys

[Christian Ehrlicher]

Maybe you can check if the dcb contains a difference when it works (so when it was first started on linux) and when not. Don't know if it helps though.

[addebito]

@Christian-Ehrlicher Thanks but I've already done when, in my previuos post I wrote "This is my last test for today...."

[addebito]

Even though I haven't solved it I'd like to give you a big thank you.

@Christian-Ehrlicher
@J-Hilk
@KroMignon
@kuzulis
@ollarch
@Pablo-J-Rogina

I'll try to contact the board supplier to investigate if there was some fw changes.

[Christian Ehrlicher]

@addebito Sorry, overread it :)

But I think you have enough to ask the supplier for help since it can be simply reproduced with plain WinAPI calls :)

[addebito]

@Christian-Ehrlicher Yes you are right !! ....after 2 days of testing!

[ollarch]

@addebito look at this https://www.hhdsoftware.com/
"Serial Monitor" app is ok.

[kuzulis]

Also you can use the following software , seems it is free.

[addebito]

just a follow up... it was a firmware problem.

[caicx]

@addebito , I have an issue more or less the same as you.

I suppose the main issue comes from one program that has opened the serial port and initialed any DCB parameters, when your Qt program opens the device, Qt driver does not reset all DCB data, but some parameters did not suitable for QtSerialPort, so the issue comes up.

here is a DCB that first open after the PC reset:

here is a DCB being opened by another program, it changed XoffLim/XonLim

so, I write some code clear DCB before Qt open serial port:

#if (defined (_WIN32) || defined (_WIN64))
void clearSerialPort (const QString &path)
{
    #include <winbase.h>

    QString deviceString = path.startsWith(QLatin1String("COM"))
                            ? (QLatin1String("\\\\.\\") + path) : path;

    HANDLE handle = ::CreateFile(
                reinterpret_cast<const wchar_t*>(deviceString.utf16()),
                GENERIC_READ | GENERIC_WRITE,
                0, nullptr, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, nullptr);
    if (handle == INVALID_HANDLE_VALUE) {
        return;
    }

    DCB dcb;
    memset(&dcb, 0, sizeof(DCB)); //::ZeroMemory(dcb, sizeof(dcb));
    dcb.DCBlength = sizeof(DCB);

    if (::GetCommState(handle, &dcb)) {
        dcb.XoffLim = 0;
        dcb.XonLim = 0;
        ::SetCommState(handle, &dcb);
    }

    ::CloseHandle(handle);
}
#endif