Passing booleans to LabView dll

I have created a Labview vi (7.1) that I have converted to a dll which uses a cluster of Booleans as a input. I set Test Stand (2.0) to pass a Structure (1 byte boundary) with Booleans as the data type (Test Stand also asks for a numeric type for some reason); is this the correct method? I get the message 'no type information in the dll' when loading the dll from Test Stand, is this normal for Structure/Cluster passing?

Hi Steve,
the No type information relates to the parameters being passed, so you have to make it up yourself in TestStand to match the setup you've given in LabVIEW when you built the .dll
LabVIEW packages booleans as U8's, so that's why it's asking for a number - there is no BOOL type itself - we address by byte only.
http://digital.ni.com/public.nsf/websearch/DBCE27265FFB554986256C9400026FE8?OpenDocument
This means that booleans are essentially a complex type, however useing U8s instead uses the same amount of space, and if you're not using clusters to simply keep them together, then you'll get prototype information out.
Useful other threads below :
http://forums.ni.com/ni/board/message?board.id=170&message.id=122260&requireLogin=False
http://forums.ni.com/ni/board/message?board.id=330&message.id=6140&requireLogin=False
Hope that helps
Sacha Emery
National Instruments (UK)
// it takes almost no time to rate an answer

Similar Messages

Passing boolean values to DLL

Hi,
Currently I am using VB .NET to pass a boolean to a DLL... i've tried this with Strings and did not have a problem... but when i want to pass booleans over, i got a 'System.EntryPointNotFoundException' error ...
i suspect the problem lies with LabVIEW not accepting boolean as 'True' or 'False', or '1' or '0'... or am i wrong?? any help is greatly appreciated ...
attached is a simple code... hope i did it correctly...
Best Regards,
JQ
LV 8.0 user...
Attachments:
display.zip ‏66 KB

JQ wrote:
thanks tst and dave... i think this may be the problem ...
In LabVIEW, a Boolean is one byte. In Microsoft Visual Basic, a Boolean is two bytes. In Microsoft Visual Basic, if you declare variables as Booleans, the memory becomes corrupted or overwritten. Instead, you must declare each variable as one byte. The Booleans are passed by ref because they are set up as pointers to values.
quoted from: http://zone.ni.com/devzone/cda/tut/p/id/3188#toc1
although this is VB... but i think VB and VB .NET should be using the same data type.. if i succeed i'll inform you guys again... thanks a lot for the help...
And in Win32 API a BOOL is 32 bit. It's amazing how even Microsoft can not decide what is best.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

LabVIEW DLL 2D Array output deallocation

Hey everyone,
I am using a custom built DLL made with LabVIEW. One of the functions outputs a 2D array of data by "handle". I can catch the 2D array from the function just fine from within my C program, however I have a question about deallocating the memory allocated by the LabVIEW DLL for the 2D array.
I call the DLL function repeatedly in a loop and as this occurs the RAM used on my machine continues to increase until it is full or I exit the program. There are no other dynamically allocated peices of data within the C program that could be causing this.
The question is, can I call free() on the 2D array handle safely? Is this the correct way to deallocate the 2D arrays passed out of LabVIEW DLL functions? One dimension of the 2D array is always the same size, but the other dimension varies per call.
Here is an example (I have renamed function calls and library headers due to security reasons):
#include "DLLHeader.h"
int main(void)
    ResponseArrayHdl myArray = NULL;
    DLL_FUNC_InitializeLibrary();
    DLL_FUNC_ConfigurePortWithDefaults("COM3");
    DLL_FUNC_StartAutoSend(9999999);
    while(DLL_FUNC_IsTransmitting())
        DLL_FUNC_GetAllAvailableResponseMessagesByHndl(&myArray);      // gets the 2D array
        // do something with array data here!
        free(myArray);   // is this the appropriate way to clean up the array?
        Delay(0.05);
    DLL_FUNC_GetAllAvailableResponseMessagesByHndl(&myArray);      // gets the 2D array
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    free(myArray);   // is this the appropriate way to clean up the array?
    DLL_FUNC_ShutdownLibrary();
    return 0;
from DLLHeader.h:
typedef struct {
    } ResponseMessage;      // created by the LabVIEW DLL build process
typedef struct {
    long dimSize;
    ResponseMessage Responses[1];
    } ResponseArray;
typedef ResponseArray **ResponseArrayHdl;   // created by the LabVIEW DLL build process
I want to make sure this is an appropriate technique to deallocate that memory, and if not, what is the appropriate way? I am using LabVIEW 7.1 if that matters. The C program is just ANSI C and can be compiled with any ANSI C compliant compiler.
Thanks!
~ Jeramy
CLA, CCVID, Certified Instructor

Tunde A wrote:
A relevant function that will be applicable in this case (to free the memory) is the "AZDisposeHandle or DSDisposeHandle". For more information on this function and other memory management functions, checkout the " Using External Code in LabVIEW" reference manual, chapter 6 (Function Description), Memory Management Functions.
Tunde
One specific extra info. All variable sized LabVIEW data that can be accessed by the diagram or are passed as native DLL function parameters use always DS handles, except the paths which are stored as AZ handles (But for paths you should use the specific FDisposePath function instead).
So in your case you would call DSDisposeHandle on the handle returned by the DLL. But if the array itself is of variable sized contents (strings, arrays, paths) you will have to first go through the entire array and dispose its internal handles before disposing the main array too.
Rolf Kalbermatter
Message Edited by rolfk on 01-10-2007 10:43 PM
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

How can I calling LabView DLL within LabView and pass similar Data Types?

I am trying to use an Instrument Driver, which is created in LabView6.1 as a DLL. At this point I have only LabView to test this DLL. I was wondering, is there easy way to find out what sort of Parameter or Data Type I should be using.
How can I pass the following data with in LabView:
LVRefnum as Type?
LVBoolean as Type?
TD1 (a structure) as Type?
It is funny to see that I am able to create a DLL in labview but having trouble calling it within LabView. I thought, it would be easier to test the DLL within the same environment.
Basically, I am more worried about the VISA calls that are used in the driver to communicate with instrument. Because, there is no link to �VISA32.dll� in
the header file, is that handled by the LV Run-time engine? I guess more details are needed on using the LabView DLL within LabView from National Instrument Technical Support.
Attachments:
RL5000.h ‏1 KB

A LVRefNum seems to be an unsigned long data type (32bit). You can cast it
in LV then use that as a parameter to call the DLL. (an Occurrence type
seems to be a Ulong32)
When you created the DLL what was the resulting type for the LVRefNum?
Happy Holidays
"Enrique" wrote in message
news:[email protected]..
> I see...
>
> After doing some research, it seems to me that there is no easy way to
> find out the type of data, other than looking at the header file and
> have documents like Using External Code in LabVIEW handy. The
> following information is from that document:
>
> LVBoolean is an 8-bit integer. 1 if TRUE, 0 if FALSE.
>
> LabVIEW specifies file refnums using t
he LVRefNum data type, the
> exact structure of which is private to the file manager. To pass
> references to open files into or out of a CIN, convert file refnums to
> file descriptors, and convert file descriptors to file refnums using
> the functions described in Chapter 6, Function Descriptions.
>
> I know you are creating a dll in LabVIEW, but I am pretty sure the
> information applies as well and is useful. For your dll this can be
> interpreted that, rather than passing a LVRefnum, try passing the file
> descriptor.
>
> From the header file, is can be deduced that TD1 is a cluster in
> LabVIEW.
>
> You are right in saying that "more details are needed on using the
> LabView DLL within LabView from National Instrument Technical
> Support.".
>
> Enrique

How to pass Visa Resoure Name parameter to labview dll in labwindows/cvi

Hi, everyone
I build a dll from labview, the prototype is : double getchannelpower(double f, uintptr_t *VISAResourceName);
I don't know how to pass VISAResourceName to this function.How can I get the VISAResourceName of this type(uintptr_t *)?
Is it related to the paremeter ViPSession in function viOpen(ViSession sesn,ViRsrc rn,ViAccessMode am,ViUInt32 ti,ViPSession vi)?
BRs,
lotusky

1. uintptr_t *VISAResourceName in the labview dll is connected to viOpen function as input parameter internally.
2.I can call the labview dll in labview via CLF Node, when the VISAResourceName parameter is set to Numeric(32-bit int or 32-bit usigned int) OR Adapt to data(Handle by Value). And I got the value of the VISAResourceName parameter, which is 0; When I directly connect 0 to the dll, it still works. But in labwindows, when I pass 0 to the VISAResourceName parameter of the dll function, I got a FATAL RUN-TIME ERROR: The program has caused a 'General Protection' fault.
mkossmann 已写：
Could you check what exactly uintptr_t *VISAResourceName in your labview dll does.Might it be that it is connected to the labviews Dll internal ViOpen() ViSession output parameter ?. And the name VISAResourceName is misleading.
Another idea would be that Labview uses 32bit Unicode for the ResourceName. And you have to convert the C String to that Unicode first.

How to call labview DLL from C#, passing char, char[], float[], long, short

Hi,
I'm having trouble calling labview dll from C# to perform certain function.
The function supposed to return the values in the float Analysis[] array. However, when I execute it it only returns zero values.
It seems that some parameters are not properly passed to the dll.
Below is the function in the header file:
void __stdcall Optical_Center(char FileDirectory[], long ImagePtr,
    short int Height, short int Width, char ReadFromFile, float Analysis[],
    long lenAnalysis);
and my corresponding dll import in c#:
[DllImport(@"SMIA.dll", CharSet = CharSet.Ansi)]
        public static extern void Optical_Center([MarshalAs(UnmanagedType.LPStr)]string FileDirectory, long ImagePtr,
            short Height, short Width,char ReadFromFile, IntPtr Analysis,
            long lenAnalysis);
string str = @"C:\SMIA.raw";
int len = 3;
long m_lenAnalysis = 3;
long m_ImagePtr = 0;
short m_Height = 2464;
short m_Width = 3280;
IntPtr m_PtrArray = Marshal.AllocHGlobal(len * Marshal.SizeOf(typeof(float)));
char m_ReadFromFile = '1';
Optical_Center(str,m_ImagePtr,m_Height,m_Width,m_ReadFromFile,m_PtrArray,m_lenAnalysis);
float[] m_Analysis = new float[len];
Marshal.Copy(m_PtrArray, floatArray,0,len);
Marshal.FreeHGlobal(m_PtrArray);
string printstr = "";
for (int i=0; i<len; i++)
    printstr = printstr + floatArray[i].ToString() + "\n";
MessageBox.Show(printstr);
Appreciate if anyone can help, thanks.
KL

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
and it worked as it should, when tested from LV.
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.

How do I pass a 1D LabView array as a pointer to an array in a C DLL?

Hello,
I am trying to pass a 1D Labview array of DOUBLE to a C DLL which is expecting a pointer to an array of DOUBLE. I have read that LabView stores arrays as a pointer to a pointer and that the first element of a LabView array is actually the size of the array. So I think my question is then how do I dereference the first pointer and pass in a pointer which points to the second element in the array?
Any thoughts out there?
Thanks!

Hi justyou,
There are many, many resources on this topic, so I will guide you to the two most useful ones:
The "Call DLL.vi" example that ships with LabVIEW explains how to use almost any data type when executing DLLs. The "Call DLL.vi" can be found by browsing the Example Finder.
Integrating DLLs. This page is the portal for DLL interation related resources. Read the tutorials and try the examples...
This should give you some ideas.
Have fun!
- Philip Courtois, Thinkbot Solutions

Pass array to "Labview 7" DLL in Visual Basic

Hi!
I would like to pass arrays in Visual Basic to a LV DLL made in Labview 7.
I've seen the examples of NI to create a dll in Labview for Visual Basic and for passing arrays, but all the examples were made with Labview 6.
The problem is that in the tutorial they say to define the Pass By of the argument as Array Data Pointer, but in Labview 7 when I add an array as an argument I don't have that option.. It's always defined as TD1Hdl* inArray, and in Labview 6 it was defined as float64 inArray[].
Can I use the TD1Hdl structure in Visual Basic? How do I use it?
Thanks!

Unfortunately, i'm not expert in Visual Basic, i need to investigate in your problem.
See link below, that explain how you can use LabVIEW DLL in Visual Basic.
http://venus.ni.com/stage/we/niepd_web_display.DISPLAY_EPD4?p_answer=&p_guid=B45EACE3D9E556A4E034080...
http://forums.ni.com/ni/board/message?board.id=170&message.id=100151&requireLogin=False
http://zone.ni.com/devzone/devzoneweb.nsf/Opendoc?openagent&4303F9807BFE234486256906007259EF
Regards,
Christophe S.
FSE East of France І Certified LabVIEW Associate Developer І National Instruments France

Passing Array of Srings between Visual Basic and Labview dll

I have searched and searched for the correct way to pass an array of
strings between Visual Basic 6.0 and a Labview 7 dll. So far, I still
do not know how to pass the array. When I create the dll in LV, the
array of strings is presented as a string, not an array. I am familiar
with passing arrays of type double, but I really need to know how to
pass an array of strings. Any and all help is appreciated.
Bob

Hey Bob,
From what I understand, that can get kind of messy. You have to allocate the memory in VB in the format that LabVIEW expects (see the externalcode.h file in National Instruments\LabVIEW 7.0\cintools for details). Then pass a pointer to that location to LabVIEW. There are a couple of related examples online. They don't necessarily show how to pass an array of strings to VB, but they should show how to pass a string and an array. I hope this helps.
Using Microsoft Visual Basic to Call LabVIEW DLLs That Pass String Data Types
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B123AE0CB9B0111EE034080020E74861&p_...
Using Microsoft Visual Basic to Call LabVIEW DLLs That Pass Array Data Pointers
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3D9E556A4E034080020E74861&p_...
Regards,
Chris J

Why does LabView dll not work in C Thread?

Hello Everybody,
I want to use a LAbView Application as Dll in a Console Application.
There is an Example Available (DLL_Example.zip)in (Displaying the Front Panel of a LabVIEW-Built DLL Function)
When I use this Example in a Windows Console Application, it Works fine (It is important for me, to see the LV Window!)
Code example:
/* Example Start *******************************************/
int main(int argc, char* argv[])
double Y = 4;
double X = 5;
double Result = 0;
SimpleCalculator(1, Y, X, &Result);
printf("Result = %f", Result);
return 0;
/* Example Stop *******************************************/
When I use the function "SimpleCalculator" in a Thread, the LabView Window never appear, what's wrong?
Code example:
/* Example Start *******************************************/
DWORD WINAPI LVThread(LPVOID lpParameter)
double Y = 4;
double X = 5;
double Result = 0;
SimpleCalculator(1, Y, X, &Result);
printf("Result = %f", Result);
return 0;
int main(int argc, char* argv[])
DWORD ThreadID;
CreateThread(NULL,0,LVThread, NULL, 0, &ThreadID);
getchar();
return 0;
/* Example Stop *******************************************/
I'm using Microsoft Visual Studio 6.0. and LabView 7.0
Thanks for every help.

bobby wrote:
Hello Everybody,
I want to use a LAbView Application as Dll in a Console Application.
There is an Example Available (DLL_Example.zip)in (Displaying the Front Panel of a LabVIEW-Built DLL Function)
When I use this Example in a Windows Console Application, it Works fine (It is important for me, to see the LV Window!)
Code example:
/* Example Start *******************************************/
int main(int argc, char* argv[])
double Y = 4;
double X = 5;
double Result = 0;
SimpleCalculator(1, Y, X, &Result);
printf("Result = %f", Result);
return 0;
/* Example Stop *******************************************/
When I use the function "SimpleCalculator" in a Thread, the LabView Window never appear, what's wrong?
Code example:
/* Example Start *******************************************/
DWORD WINAPI LVThread(LPVOID lpParameter)
double Y = 4;
double X = 5;
double Result = 0;
SimpleCalculator(1, Y, X, &Result);
printf("Result = %f", Result);
return 0;
int main(int argc, char* argv[])
DWORD ThreadID;
CreateThread(NULL,0,LVThread, NULL, 0, &ThreadID);
getchar();
return 0;
/* Example Stop *******************************************/
I'm using Microsoft Visual Studio 6.0. and LabView 7.0
Thanks for every help.
Check out luciangeeks's explanation elsewhere on this forum in several threads about the message loop needing to be pumped by the intial thread starting up the LabVIEW runtime system. In Windows console applications the hidden startup code linked in from the C runtime library to intialize the environment before passing control to the console applications main function also contains a message loop, polling the Windows message queue to among other things translate those messages into keychars so that the C runtime library function getchar() and friends can work as expected. It also makes the console application look responsive to the Windows system so that Windows doesn't think it would need to shutdown the application. LabVIEW DLLs really running as GUI components can't work without an active message loop making sure those system messages are retrieved and distributed to the according (usually hidden) VI windows. However the setup in Windows makes it such that a DLL sort of inherits the message loop of the thread which first entered that DLL. If that thread does not have a message loop, LabVIEW windows simply can't work properly and this means that the LabVIEW code is not managed properly and therefore won't run.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Problems in using Labview DLL with TestStand!

Hi,
I tried to put the VI's to create a TCP/IP Connection, read/write Data to it and close it inside a LabVIEW DLL and use these functions with TestStand.
The problem is to get access to the ConnectionID generated as TCP Network Refnum in LabVIEW.
I don't know how to specify the prototype entry for this Refnum in LabVIEW and how to read it with TestStand.
Another try to pass an ActiveXReference of SequenceContext and use the SetValIDispatch method to set a local variable (Type: ActiveXReference) to the returned ConnectionID of the TCPOpen.VI wasn't successful too.
It seems to me that the connectionID isn't a normal ActiveXReference.
Regards,
Sunny

Hi Sunny -
You should treat this parameter as a pointer to an int when calling the DLL from TestStand (or any language like C or C++). Note that you can't do anything with the value outside of LabVIEW since it only has meaning inside of LabVIEW. You can only pass it around for use in other VIs you call from TestStand.
Hope this helps....
Kyle G.
National Instruments
Kyle Gupton
LabVIEW R&D
National Instruments

Using PostLVUserEvent function from Labview.dll

I am trying to use the PostLVuserEvent function from the labview.dll and corresponding extcode.h file. I have made my own dll using CVI that uses this function. I then use Labview to call my dll. My dll compiles fine. No issues, no errors. LabView can call my dll function containing the PostLVUserEvent function with no errors. However, the event number LabView passes my dll is not the same event number I receive so no LabView event is triggered.
Has anyone had this issue?
We are trying to solve it from the LabView side and the CVI side but cannot seem to get it to work. The examplesI have found here were compiled using C++ and those seem to work. I do not know why when I compile my program in C, it creates the dll but does not work. If I had to guess, i think it's an issue with pointers vs non-pointers. When the LAbview program selects my function from the dll, it shows the argument PostLVUserEvent as a pointer when in my dll, it is not a pointer PostLVUserEvent....
Any ideas?
Thanks in advance.

Hello Blue
Take a look to this one, it was created on C, I think the .c and the .h files will give a good idea, how the function should be implemented. It is important when calling the dll on LabVIEW, to use the std calling convention and run it on the UI thread.
Regards
Mart G
Attachments:
LabView EventTest.zip ‏1041 KB

Calling LabView DLLs from C/C++

Hi!
Is it possible to call functions in the LabView DLLs directly from
C/C++?
Functions like InvChiSquare in lvanlys.dll has "Adapt to Type" void *
parameters. How do I specify those parameters from C/C++?
I have tried to use the "Build Shared Library" function in LabView to
make a wrapper dll of the "Inv Chi Square Distrubution" vi, but when I
call this function in the dll from C/C++ the function never returns.
Other functions in the same dll that does not use functions in the
lvanalys.dll are working ok.
Regards
Hans Forssell

There are 2 great places to get infomraiton on passing data to dlls, and the data types used. First would be this manual. Using External Code in LabVIEW
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Interop.LabVIEW DLL

Where can I get a copy of the Interop.LabVIEW DLL for use with C#, or do I have to write my own?
Solved!
Go to Solution.

The project requires:
1. My vi recieving a digital input and then triggering my wpf to start a webcam running.
2. my vi then recieves a second digital input and that triggers my wpf to capture and save an image from the webcam to file or for that image to be sent directly to my vi.
3. the captured image will be compared to a reference image and if the illumination of the object is not the same as that of the reference image my vi will adjust the illumination level of the object (this process will cotinue until the illumination level of the object anf reference image are equal).
4. Once the captured image is equal to the reference image my vi will begin image processing to determine the orientation and feature recognition of the object by comparison to the reference image.
5. if the orientation and/or features of the object are incorrect my vi will send a digital signal to have the object rejected (my vi will also sound an alarm buzzer and start an LED flashing).
6. If the object passes inspection then the orientation and co ordinates of the specific features that need to be identified will be saved to file.
7. With 6 completed or the object rejected my vi will send a signal to my wpf to stop the webcam. and wait for the input signal to start
the whole process all over again.
So i will be using the DLLs that are available via the references window in visual studio 2010. but i dont know what namespaces, classes and methods are available in those DLLs so i bont know how to use them. but i looked on the internet and i think the DLLs that are available via vs2010 are to allow communication between both my wpf and vi via .net objects and/or active x objects.
Ive no idea how to use either and finding anything more than superficial documentation on using either of the above is proving difficult to find (could you point to anything useful on .net and/or active x).
I think ive covered all you wanted to know but if you require more info please let me know, and thank you for trying to help me.
Saving to file isnt a problem but the communication between my vi and c# based wpf is.

NO access to certain cells when passing 2D array to DLL

I am trying to feed a 2D array (image reading) to a DLL, but it always gives a 1097 error. I debugged the original C++ code. It narrows down to the point that some pixels cannot be read. So I write a simple C code to reproduce the issue.
As you can see from the following screenshot, this C code simply returns the number indexed by 'index'. When fed from Labview to the DLL, I chose to feed a 2D array as 'Array Data Pointer'. Then I put it in a for loop to read through the entire array. The returned array showed that the cells after 75th row cannot be read with a 1097 error. But why? What did I do wrong?

Yes, initialize-array initializes a table of I32, and the type in the CLF matches, but the DLL is still indexing into (what it thinks is) an array of Double - see the function syntax the C source-code: "(double *x",...).
If you simply change the initialize-array type to U64, it will allocate enough space. It's not even necessary to correct for type conversion - you're still passing a pointer, the DLL will be happy.

Passing booleans to LabView dll

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