Calling a Visual C++ dll from CVI

I created a dll in visual C++, try to access it using .Net library APIs of CVI.
I am able to create the object of the class “Class1” correctly, but when I try to invoke a function of the class, I got error -6587(inaccessible error).
I attached my code, dll code for your reference.
Attachments:
Maxnumeber.zip ‏3 KB
test1.zip ‏820 KB

Can you provide a screen shot of the error you are receiving? Have you marked the functions you are trying to call with extern C to specify that they are going to be used with the C compiler? Please see the followling link which discusses this topic.
http://www.ni.com/white-paper/3341/en#toc9
Regards,
Anjelica W.
National Instruments
Applications Engineer

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I get error 998 when calling a LabVIEW buildt DLL from MSVC++

I created a DLL in LV 6.0.2. This DLL contains 39 VIs and controls. 13 of the VIs are exported, the others are subVIs, which one of them is a dynamic VI.
I do not have all connectors used by defining the VI prototype in the build file for the application builder.
Using this DLL I get four effects:
From LV 6.0.2 FDS all works fine until I quit LV immediatly after the application VI stoppes. Then LV wants to save some of the VIs of the DLL.
If I do the same but close the VI before I quit LV one want save anything.
After Building an exe from the application VI and running the exe all works fine. The VI will only stop and if I close or quit noone wants to save something.
Then I built an application with M
SVC++ 6.0 using this DLL. There will be no errors or warnings during the build. If I start the application i get an error message dialog with the number 998 stating "system error loading LV Runtime engine. My application needs a Version 6.0 or compatible Runtime-engine". The path to teh Runtime-engine is given in the dialog and the lvrt.dll there has version 6.0.2.
Does someone run on such a problem?
Has someone a solution to this?
Waldemar
Using 7.1.1, 8.5.1, 8.6.1, 2009 on XP and RT
Don't forget to give Kudos to good answers and/or questions

Waldemar,
I. LabVIEW wanting to save VIs
The DLL created is just a group of VIs, not actually compiled DLL code. When the subVIs are called, they might be cached from the disk copy, not the one in the DLL. LabVIEW then loads the separate copy of that subVI. It will then ask if you want to save changes because there were value changes when it was run (this makes since) or it is in LabVIEW 6.0 version and has not been mass compiled for LabVIEW 6.0.2. When it is compiled to an exe, the search path for the subVIs goes through the executable and not the LabVIEW development environment. Also, saving VIs is not an option in an executable so the save dialog does not pop up.
II. MSVC++ error
This is actually a Microsoft issue. It has something to do with static and
dynamic linking of the MFC DLL. Our R&D engineers have verified this with projects created with no LabVIEW code at all (that is why we believe it to be solely a Microsoft issue). There are three options at this time:
1. Link with the DLL form of MFC.
2. Do not link with the .lib from the LV DLL, instead use LoadLibrary and GetProcAddress to dynamically load the DLL and call the function.
3. Use the VC delayload feature to make the LV DLL not get loaded until the first call is made into it. See VC help on "delayload" for information on setting this up.
Randy Hoskin
Applications Engineer
National Instruments
http://www.ni.com/ask

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Hi
I want an immediate help from u all.
I have athird party c dll with .h and .lib file
I wont be able to cahnge any thing in those files.
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Ist possible to call the dll without writing any c or c++ wrapper over it?if yes , how to do it?

Hi,
You may use a generic wrapper like JNative.
Commercial wappers also exists.
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How do I call a LabVIEW created DLL from within Microsoft Excel (VBA)?

Hi,
I'm trying to get Microsoft Excel 2003 to call a function stored in a dll that I created using LabVIEW 7.1. The function is very simple and is called "binary_file_to_ascii". Basically it just reads a LabVIEW created binary spreadsheet file and outputs the columns as float arrays.
The function arguments are as follows:
INPUT : String that contains the path to the binary spreadsheet file
OUTPUT : Number of rows in the spreadsheet
OUTPUT : Number of columns in the spreadsheet
OUTPUT : Float array containing the elements in column 1
OUTPUT : Float array containing the elements in column 2..
OUTPUT : Float array containing the elements in column 11
However, for some reason there is something wrong with my VBA code and/or the way I created the DLL in LabVIEW because Excel crashes when it loads my DLL.
What do I need to change in my VBA code or my LabVIEW DLL build settings to fix this?
I've attached to this post a ZIP file that contains all my code and a sample binary file.
Your help with this will be much appreciated. Thanks!
Richard
P.S. Here is the VBA code I'm using:
Private Declare Function binary_file_to_ascii Lib "C:\temp\binary_file_to_ascii\binary_to_ascii.dll" _
(ByVal binaryFile As String, ByVal nrows As Long, ByVal ncols As Long, ByVal column1 As Variant, _
ByVal column2 As Variant, ByVal column3 As Variant, _
ByVal column4 As Variant, ByVal column5 As Variant, _
ByVal column6 As Variant, ByVal column7 As Variant, _
ByVal column8 As Variant, ByVal column9 As Variant, _
ByVal column10 As Variant, ByVal column11 As Variant)
Private Sub load_binary_spectra()
Dim nrows, ncols As Long
Dim col1(), col2(), col3(), col4(), col5(), col6(), _
      col7(), col8(), col9(), col10(), col11() As Variant
Dim lRetVal As Long
Dim spectra_path As String
    spectra_path = "C:\temp\binary_file_to_ascii\sample_binary_file\sample_binary_file.dat"
    lRetVal = binary_file_to_ascii(spectra_path, nrows, ncols, _
              col1(), col2(), col3(), col4(), col5(), col6(), _
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End Sub
Message Edited by Richard Ballantyne on 07-25-2007 02:39 PM
Message Edited by Richard Ballantyne on 07-25-2007 02:39 PM
Attachments:
binary_file_to_ascii.zip ‏192 KB

Hi,
I don't know anything about Visual Basic, but here's my guess.
When you load the DLL with this line of code
Private Declare Function binary_file_to_ascii Lib "C:\temp\binary_file_to_ascii\binary_to_ascii.dll" _
(ByVal binaryFile As String, ByVal nrows As Long, ByVal ncols As Long, ByVal column1 As Variant, _
You are defining how the parameters are sent. It seems that all are sent by value (ByVal), but in the DLL header, some of the function's
parameters are defined as pointers(see the function prototype below, look for asterisk(*))
void __stdcall binary_file_to_ascii(PStr binaryFile,
                                                long *numberOfRows,
                                                long *numberOfColumns,
                                                float column1[],
                                                float column2[],
                                                float column3[],
                                              float column4[],
                                                float column5[],
                                                float column6[],
                                                float column7[],
                                                float column8[],
                                                float column9[],
                                                float column10[],
                                                float column11[]);
Can you define in VBA that you want to use pointer instead? Maybe by using ByRef (as by reference).
Hope this helps.

Calling existing C/C++ dll from Java Prog

Hi,
From within the Java code I want to use the
functionality of an existing C API. The dll's of C are available. Is it possible to directly call the C Api using Jni or some other technique or do I need to implement a native method in C which would Use the existing C Api to get the values and Pass them to the Java prog.
Istikhar.

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I'm trying to use the Windows call GetFileVersionInfo in the version.dll file to get the version info of an executable. Either I get garbage back for the version info or LV crashes. I am able to call GetFileVersionInfoSize successfully. I know these calls can be tricky and I probably don't have the parameters right, but I'm at a loss for what to try next. I've included the VI I'm using.
Attachments:
fileinfo.vo.vi ‏13 KB

A few things...
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http://detritus.blogs.com/lycangeek

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// extract of code in ECard.cpp
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#import "D:\Archivos de programa\Datacard\ID Works\bin\PrintServer.DLL"This is the java code part
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Please help me I�m desperate...

How to call a labview dll from excel-VBA?

How to call a simple Labview DLL from Excel VBA?
I have seen examples of DLL calls from VB but does it work the same way for VBA? I have 2000 excel and Labview 8.5. I created the DLL and tried to call it from VBA using the same type of code as in NI's website example(ofcourse its a bit diff with 8.5)
http://zone.ni.com/devzone/cda/tut/p/id/...
BUT it errors out when called from excel
ERROR: The object invoked has disconnected from its client

You would need to provide more details about the LabVIEW DLL, such as the prototypes of the functions (VIs) that you're trying to call, and your actual VBA code. Specifically, what object you're trying to create. You should also make sure the Run-Time Enginer is installed, as well as any required libraries such as the VISA Run-Time if you're using VISA. Have you made sure to enable the ActiveX server for the DLL?
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http://forums.ni.com/ni/board/message?board.id=170&message.id=261345&requireLogin=False
http://forums.ni.com/ni/board/message?board.id=170&message.id=45099&requireLogin=False
http://forums.ni.com/ni/board/message?board.id=170&message.id=299209&requireLogin=False
http://forums.ni.com/ni/board/message?board.id=170&message.id=195846&requireLogin=False

Calling LV DLL from VB

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I used Standard calling convention when making DLL from LV.
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Private Declare Sub OSAMeasurement Lib "C:\ADE\OSAMeasurement.dll" Alias "OSADFBMeasurement" _
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ByVal FileName As String, _
ByVal File_Path As String, _
ByVal Start_Wavelength_nm As Double, _
ByVal Stop_Wavelength_nm As Double, _
ByVal Level_Scale_dB As Double, _
ByVal Res_nm As Double, _
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ByVal Peak_Level As Double, _
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ByVal Mode_Offset As Double, _
ByRef Level_Array() As Double, _
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Here is my VB call:
Call OSAMeasurement(Form1.OSA.PrimaryAddress, _
(strOXM & Form1!txtOPMNumber), _
(CStr(CInt(dblSetVoltage)) & "v_Scan.txt"), _
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Bad DLL calling convention
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Any suggestions/comments?
Attachments:
OSA.zip ‏703 KB

Basically what i want to do is to call the microchip's dll called "mpusbapi.dll" from VB6. This dll is written in C++. This dll has some basic functions of usb like MPUSBRead() , MPUSBWrite , MPUSBOpen() etc.
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Any help greatly appreciated
Attachments:
_mpusbapi.cpp ‏42 KB
_mpusbapi.h ‏19 KB

Calling external C dll from Portal

I have been trying to find the best way to call an external c dll from portal. In forms we used a built-in ora_ffi to make the call. What is the best way to do it in portal. Would I need to call from plsql using the extproc?

depends where the DLL is living.. if you were building the portlet in Java on the midtier you could use JNI to access the DLL. If the DLL is on the infrasture tier then you would need an access method from PLSQL

Calling 64-bit dll from labview 8.2 on Windows7

Hello,
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So I have tried calling the OmniDriver64.dll. but LABView seems not to recognised the dll and can’t read the included functions.
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There is no virtualization support for DLL bitness issues outside of the Windows standard directories. The Windows and System directories that an application "sees" depends on its bitness. All other directories are not mapped depending on the calling process' bitness.
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a division of Test & Measurement Solutions

Fall into a trouble when calling a dll from java in linux

Hi, experts:
I encountered a big trouble when using JNI to call a C++-compiled DLL from java in Linux: The DLL function didn't execute immediately after the invocation, and was deferred till the end of the Java execution. But all worked well after migrating to windows. This problem made me nearly crazy. Can somebody help me? Thanks in advance.
Linux: fedora core 8, jdk1.6.0_10,
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It looks like the OP compiled the C source file and linked it into a Windows .dll, which would explain why it worked flawlessly in Windows. (Though I must say the usage of GCC would make someone think it was compiled in Linux for Linux, GCC also exists for Windows, so I'm not sure it's a Windows .dll either...)
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Edited by: Looce on Nov 21, 2008 11:33 AM

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It is not clear from your question as to what is specifically failing. If possible, one option would be to remove TestStand from the picture and see if the problem still occurs using a CVI EXE that invokes the CVI DLL.
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How to call labview DLL from visual C++?

Hi,
I'm trying to call a LV DLL from a VC++ application
by using the LoadLibrary and GetProcAddress functions.
The DLL contains a simple sum function. The Library is
loaded correctly, but the result is always 0.0000.
I have loaded a VC++ DLL in a similar way and it works
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and it works correctly. The calling convention is defined
to be stdcall in LV Application Builder.
I have also tried this solution, but I will get a compiler error
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typedef char                int8;
and the error states that
..\fundtypes.h(107) : error C2371: 'int8' : redefinition; different basic types
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information greatly.
Below is the code that I'm using for loading the LV DLL.
Thanks
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <map>
#include <windows.h>
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I was just about to post the header file of the DLL, when
I noticed that there's a function called LVDLLStatus.
This little thingie turned out to be a rather handy tool.
With that function I found that in the DLL I had a problem
with another function that prevented the DLL to be correctly
loaded.
This other function in the DLL is for generating digital output
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Anyway if someone is interested, I got it working by using
the LoadLibrary and GetProcAddress function, as in the
source code thatI posted earlier.
I will investigate what is wrong with that digital output, and
post into a another thread if I have problems with that.

Calling a Visual C++ dll from CVI

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