Pointer to a function (C .dll files)

Question

Hi,
We have a .c dll file that we are trying to use in Labview to talk to a USB transceiver. What happens is that when we try to configure the device we call c functions using the "call library function node" utility in Labview i.e. void open_channel(char channel_number) etc.
At the start of the code, we need to send the .dll this function:
void AssignResponseFunction(RESPONSE_FUNC pfResponse, UCHAR *pucResponseBuffer); where RESPONSE_FUNC is a pointer to the function that will be called whenever a response / event message is received from the module.
When the USB device has a message that it wants to make available to us, it uses the pointer pfResponse to call a function in memory that will process the data that has been stored in pucResponseBuffer and make it available. Is this possible in Labview and how would I even go about doing such a thing?
Ken

Answer 1

hi,
first of all, thanx for the advice.
i tried to write the dll, that passes the procaddress to the funtion that needs it. i made a dll with the appbuilder that matches the prototype of the callbackfunctio (expet that the returnvalue isnt bool but an uint).
the next thing i have done is to write a dll in visual c++. as i am no programmer at all, i tried to get this done with some books and the internet, but i fail.
i wrote following code:
#include "stdafx.h"
#include <windows.h>
HINSTANCE h = 0;
const char* lib ="MeineDLL.dll";
const char* proc="DLL Funktion";
extern "C" __declspec(dllexport) int myDLLload(LPCWSTR lib)
if(h == 0)
LPCWSTR lib = libinput;
h = LoadLibrary(lib);
return 0; // ok
return 1; // error
// übergib addr in LabView der anderen DLL-Funktion
extern "C" __declspec(dllexport) int myDLLgetprocaddr(LPCSTR proc, int* addr)
if(h != 0)
*addr = (int)GetProcAddress(h, proc);
return *addr != 0; // ok
return 1; // error
extern "C" __declspec(dllexport) void myDLLFree()
FreeLibrary(h);
the problem is, that the myDLLload function returns 0 all the time, no mather how i define "lib". and i think that is the reason why the myDLLgetprocaddress funktion fails to deliver me the address...
i know that you surely know much more about visual c++ than i do, so i would be very thankfull for any advice how i can solve this problem.
thank you a lot
martin