serial port in dll

chr_sch

Hi at all,

I want to write a dll file , using a serial port.
I will describe what the dll should do:
I call the function of the dll in a measurement programm. The function should accept 6 initial values, which should be send to a microcontroller. So in the dll I want to use the QtSerialPort and send the values to my microcontroller.

I wrote a dll but when I try to run it in a test programm I get a lot of errors:
" LNK2019: Verweis auf nicht aufgelöstes externes Symbol ""__declspec(dllimport) public: bool __cdecl QSerialPort::setDataBits(enum QSerialPort::DataBits)" (_imp?setDataBits@QSerialPort@@QEAA_NW4DataBits@1@@Z)" in Funktion ""public: void __cdecl Messwert_Zuordnung_DLL::Messwert_zuordnung(double,double,double,double,double,double)" (?Messwert_zuordnung@Messwert_Zuordnung_DLL@@QEAAXNNNNNN@Z)"."

Here is my dll code:
<
#include "messwert_zuordnung_dll.h"
#include <iostream>
#include <string>
#include <math.h>
#include <QDebug>
#include <QtCore/QCoreApplication>
#include <Windows.h>
#include <QtSerialPort/QSerialPort>
#include <QtCore/QDebug>

QSerialPort *serial;

void Messwert_Zuordnung_DLL::Messwert_zuordnung(double messmeth, double messint, double bauteillaenge, double interpol, double anz_messungen, double abs_messungen)
{
//Configuration of the serial port
serial = new QSerialPort;

//+++++++++++++++++++++++++++++++++++
//+++++++++++++++++++++++++++++++++++
//Adapt the 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);


     if (messmeth == 1){


        //Conversion to send (requiered by 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
        serial->write("1");
        serial->write("\n");

        serial->write(bauteillaenge_s);
        serial->write("\n");

        serial->write(messint_s);
        serial->write("\n");

        serial->write(interpol_s);
        serial->write("\n");

        serial->write(anz_messungen_s);
        serial->write("\n");

        serial->write(abs_messungen_s);
        serial->write("\n");

Maybe I have to initiate the serial port in an other way ? Can anybody help me ?

regards

t3685

This post is deleted!

t3685

Can you post your pro file?

Do you have this line in it?

QT += serialport

sneubert

Hi @chr_sch,

could you clarify if your problem is to build the dll itself, or to include the dll in another project?

chr_sch

@t3685
that´s my pro file:

TARGET = Messwert_Zuordnung_DLL
TEMPLATE = lib

QT += serialport
QT += core
QT -= gui

DEFINES += MESSWERT_ZUORDNUNG_DLL_LIBRARY

SOURCES += messwert_zuordnung_dll.cpp

HEADERS += messwert_zuordnung_dll.h\
        messwert_zuordnung_dll_global.h


unix {
    target.path = /usr/lib
    INSTALLS += target
}

serialport is added.

@sneubert:

the dll builds without a problem. But I am not shure that it works correctly in the way I created it.
In the test programm I added the .h and global .h file and set the reference to the dll file.
Here is the pro file from my test program:

QT       += core

QT       -= gui
QT       += serialport

TARGET = dll_tester
CONFIG   += console
CONFIG   -= app_bundle
LIBS += "C:\Users\Christian\Documents\build-dll_tester-Desktop_Qt_5_4_0_MSVC2013_64bit-Debug\debug\Messwert_Zuordnung_DLL.obj"
TEMPLATE = app


SOURCES += main.cpp

HEADERS += \
    messwert_zuordnung_dll.h \
    messwert_zuordnung_dll_global.h \
    qserialport.h \
    qserialportglobal.h

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 .