Link a .dll library to a Qt project

[n3500]

Hi !

I am actually working on a project which enables connection to a datalogger Campbell.
Campbell provides a simplepb.dll to communicate with datalogger, and I would like to use it in my project.
You can download it here.
I put this dll and the header in a DLL directory located on C:

I changed the .pro file into:

INCLUDEPATH += C:/DLL
LIBS += -LC:/DLL -lsimplepb -lcoralib3d

INCLUDEPATH += C:/DLL
LIBS += -LC:/DLL -lsimplepb -lcoralib3d

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The header:

#ifndef FUNCTIONS_H
#define FUNCTIONS_H
 
#include "simplepb.h"   
 
void test();
 
#endif // FUNCTIONS_H

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

#include "simplepb.h"   

void test();

#endif // FUNCTIONS_H

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The .cpp:

#include "Functions.h"
 
void test()
{
        OpenPort(1,9600); //Function of simplepb.dll
}

#include "Functions.h"

void test()
{
        OpenPort(1,9600); //Function of simplepb.dll
}

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After building with Mingw, I obtain every time the same error: ..\TestDll\Fonctions.cpp:5: erreur : undefined reference to `OpenPort@8'.

If someone has an idea to fix it !

TY