serial port in dll

t3685

At first glance it seems you are not linking to your library properly. Have a look at the link below for an example on how to link to a library.

https://wiki.qt.io/How_to_create_a_library_with_Qt_and_use_it_in_an_application

chr_sch

@t3685

I changed a few things in my .pro file according to the instructions in the link you send.
Namely I changed the following three things

INCLUDEPATH += C:\Users\Christian\Desktop\Studienarbeit\DLL\Messwert_Zuordnung_DLL
DEPENDPATH += C:\Users\Christian\Desktop\Studienarbeit\DLL\Messwert_Zuordnung_DLL
LIBS += C:\Users\Christian\Desktop\Studienarbeit\DLL\build-Messwert_Zuordnung_DLL-Desktop_Qt_5_4_0_MSVC2013_64bit-Debug\debug

But the Problem stayed ! The error refers to the QSerialPort I used.
I tried to include the DEPENDPATH and INCLUDEPATH where the qserialport.h file is in the Qt folder and added the qserialport.h file to the Header but no succes.

Any other ideas ?

regards

t3685

@chr_sch

Hello,

I think you still have an error in your pro file. The correct syntax to link to a library is

LIBS += -L<path to your dll> -l<name of your dll>

In your pro file you don't have the -l and -L. Please follow the instructions in the wiki more closely

chr_sch

@t3685

I changed it :
LIBS += -L C:\Users\Christian\Desktop\Studienarbeit\DLL\build-Messwert_Zuordnung_DLL-Desktop_Qt_5_4_0_MSVC2013_64bit-Debug\debug -lMesswert_Zuordnung_Dll

Still getting the error.

regards

t3685

@chr_sch

Hi,

Did you put a export macro in your class like explained in the wiki and on this page:

http://doc.qt.io/qt-5/sharedlibrary.html

Greetings,

t3685

chr_sch

@t3685
I added the Qt5SerialPort.lib, found somewhere in the Qt intalling folder, in the pro file under LIBS.
This generated some new errors refers to the moc_qserialport.cpp like this:

1.)..\debug\moc_qserialport.cpp:352: Fehler: C2027: using
undefined Typ "QSerialPortPrivate"
c:\users\christian\documents\build-dll_tester-desktop_qt_5_4_0_msvc2013_
64bit-debug\debug../../dll_tester/qserialport.h(45): Declaration
of 'QSerialPortPrivate'

2.)..\debug\moc_qserialport.cpp:352: Fehler: C2227: to the left of
"->_q_completeAsyncCommunication" must be an pointer to an class/strucktur/union/generic type

regards

t3685

@chr_sch

You don't need to add Qt5SerialPort.lib.
The error you are getting is that the linker cannot find the implementation of "Messwert_Zuordnung_DLL::Messwert_zuordnung".
Like I said this is either due to:

a) incorrectly linking to your dll
b) not declaring the function/class for export

Both situations are explained in:

http://doc.qt.io/qt-5/sharedlibrary.html

So if the problem persist, please make sure that both conditions are fulfilled exactly as described in the link.

chr_sch

This is my header file:

#if defined(MESSWERT_ZUORDNUNG_DLL_LIBRARY)
#  define MESSWERT_ZUORDNUNG_DLLSHARED_EXPORT Q_DECL_EXPORT
#else
#  define MESSWERT_ZUORDNUNG_DLLSHARED_EXPORT Q_DECL_IMPORT
#endif

class MESSWERT_ZUORDNUNG_DLLSHARED_EXPORT Messwert_Zuordnung_DLL
{

public:
    Messwert_Zuordnung_DLL();

    void uebergabe(double messmeth,double messint, double bauteillaenge, double interpol, double anz_messungen, double abs_messungen);
};

Therefore I think it is like mentioned in the link.

The linking to my dll consists of the following points:
-include the header files in my tets programm (copy them in the same direction)
-DEPENDPATH/INCLUDEPATH path to the folder where the .dll/.obj/.lib files are
-LIBS -L Path to dll -lname of dll
-HEADER name the headers to include

So i followed the description in the link but I just cant see where my faults are ?!
Should I send you my files ?

regards

SGaist

Hi and welcome to devnet,

Did you re-run qmake after adding QT += serialport ?

chr_sch

@SGaist

Yes I run qmake.
I tried to set the paths to the folder where my test program is.
Now I get the error:
main.obj:-1: Fehler: LNK2019:unresolved external symbol""__declspec(dllimport) public: void __cdecl Messwert_Zuordnung_DLL::uebergabe(double,double,double,double,double,double)" (_imp?uebergabe@Messwert_Zuordnung_DLL@@QEAAXNNNNNN@Z)" in function "main".

regards

SGaist

Did you check that you are doing the property symbol exporting ? Define name for activating the export macro etc. ?

t3685

@chr_sch

Do you this macro: MESSWERT_ZUORDNUNG_DLL_LIBRARY defined in the pro file of your library?

chr_sch

I choose to use QLibrary instead of implementing the dll by myself. Therefore I used the following code in my main.cpp:

 QLibrary library("Messwert_Zuordnung_DLL.dll");
    if (!library.load())
    qDebug() << library.errorString();
    if (library.load())
    qDebug() << "library loaded";

    library.resolve("uebergabe");

I am not really shure, that this is the proper use of QLibrary but it builds without an error.
So I think it might work.
If my dll gives simply the value in qDebug() out which I write in the dll function in my test programm it works.
But if I try to establish a serial connection, my microcontroller does not recognize a input. So there is a fault in the use of the QSerialPort in my code. The same code is used in a GUI where it works. I only did not use the connect() function and in the definition of my port serial* = new QSerialPort (this) I didn´t write this. Because I have no parent object here. Do I have to establish a QObject for this ? Or is there any other problem with the use of QSerialPort in a dll ?

Here is my code:

QSerialPort *serial;
 serial = new QSerialPort();


    //+++++++++++++++++++++++++++++++++++
    //+++++++++++++++++++++++++++++++++++
    //COM-Port !

    serial->setPortName("COM12");

    //+++++++++++++++++++++++++++++++++++
    //+++++++++++++++++++++++++++++++++++


    serial->setBaudRate(QSerialPort::Baud115200);
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity(QSerialPort::NoParity);
    serial->setStopBits(QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::SoftwareControl);


    serial->open(QIODevice::ReadWrite);


            //conversion of the variables for the use of the send function


            QByteArray messint_s = QByteArray::number(messint);
            QByteArray bauteillaenge_s = QByteArray::number(bauteillaenge);
            QByteArray interpol_s = QByteArray::number(interpol);
            QByteArray anz_messungen_s = QByteArray::number(anz_messungen);
            QByteArray abs_messungen_s = QByteArray::number(abs_messungen);

            //Sending the variables to my microcontroller
            serial->write("1");
            serial->write("\n");

regards

SGaist

Was it dll_tester that you failed to link ? If so, you were not linking to the library.

You need to delete serial by hand when not using it anymore otherwise you'll be leaking memory

chr_sch

@SGaist
I don´t know where my fault was. I think it was some linking problem but I don´t know how to solve so I use QLibrary.

Ok you mean that I have to close the serialport at the end of the dll ?
Can you see any other fault? Because the serial connection is not working .

SGaist

You have to delete serial. IIRC that should also close it.

In any case, you should recheck your project and make it link properly to your library. Using QLibrary as a workaround is not the proper thing to do.

chr_sch

@SGaist
Yes but this should only be a test program to see if the dll works correctly. In the end the dll is used in an othe context, so I want to focus on the function of the dll. Alltough it would be nice to know where my fault was. But I did everything like in the description in the links above nothing works, so I have to move on to loos not more time.

But why doesn´t works my serial connection ? That is in the moment my biggest problem.
Do I have to create a QObject as parent when I don´t have a window as parent ?
Is the connect function necessary ?
I thought the use is only to refer the connection fe to a button. But in a dll it should be unnecessary.

Is this maybe the troublemaker?

SGaist

Why it doesn't work ? I can't tell, that's Crystal Ball debugging at this point. However, you don't check that that your device opened successfully

chr_sch

@SGaist

Yeah that´s kind of diffucult. But I need help because I dont´t know how to figure out where my problem is.
I tried in a working serial port GUI to delete the connect() function and the "this" in new QSerialPort(this). It is still working. So the code should work.

With : if(!serial->open(QIODevice::ReadWrite)){qDebug()<<"Connection failed"}. I figured out, that the connection is not opened.

I get the return value: -1073741510. Knows anybody what this means?

regards

SGaist

Your application has been aborted e.g. you stopped it brutally.

Did you check the returned error ? What is it ?