Creating a DLL in CVI That Can Be Called from LabVIEW

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转自NI
Primary Software: LabVIEW Development Systems>>Full Development System
Primary Software Version: 5.1
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem: How do I call a DLL that I created with CVI from the Call Library Function Node in LabVIEW 5.1?

Solution: Complete the following steps to create the DLL in CVI:

Open CVI and create a new project (.prj) and a new source (.c) file.


Edit the source file and add the following header lines:

/* Include files needed to compile DLL */#include <windows.h>#include <cvirte.h>     /* needed if linking DLL in external compiler;                                  harmless otherwise */#include <userint.h>          BOOL __stdcall DllMain (HINSTANCE hinstDLL, DWORD fdwReason,                         LPVOID lpvReserved){   return TRUE;}


Add a simple function or any code you want to the DLL. Mark the functions you want to export as DLLEXPORT. The following example code multiplies a number by two.

void DLLEXPORT twise (double *my){   *my *=2;        }


Select Build &raquo; Target in CVI and change the target to Dynamic Link Library.


Select Build &raquo; Create Dynamic Link Library. Make sure the Export What field is set to Symbols Marked to Export, as shown in the example linked below.

Complete the following steps to use the DLL in LabVIEW:

Open a new VI and place a Call Library Function Node on the block diagram.


Right-click the node and select Configure from the shortcut menu.


Navigate to the DLL you created.


In the Function window, enter the name of the function you want to call, such as twise.


Set the correct parameters and data types, as shown in the example linked below.


Wire the appropriate inputs and output to and from the Call Library Function Node and set the input values. All input terminals must have something wired to them.


Save the VI.


Run the VI. If all parameters are defined correctly, the VI should run successfully.