Calling a Function node in a DLL to give force-feedback effect to a joystick (using DirectInput)

Hello,
I have been working for a couple of weeks on writing a DLL in Visual C++ Studio. My intention is to write an exported function in the DLL to initialize a Logitech Force3Dpro joystick, setup a force feedback effect and run it using DirectInput. I would like to control this force feedback effect (in particular, the intensity of the feedback) from Labview by calling the function in the DLL.
I followed the FFConst example in Microsoft SDK DirectInput Samples for making an .exe file to setup and run force feedback effects. I have been able to build the DLL successfully with an exported function that can be accessed from Labview by "Call a function node". I tested the function by running simple functions such as addition and multiplication of integers, andconfirmed the fact that the DLL was built correctly. I have also included the DirectInput code for initializing and running the force feedback effect. I am able to compile and build the DLL with no problems.
The Problem:
The only problem that I have at this point is with setting SetCooperativeLevel for the DirectInput8 joystick device. I have to provide a top-level window handle to SetCooperativeLevel so that I can give the function exclusive access to the joystick. Since I am not making a window and am building a DLL, I am not sure what handle I am supposed to provide it so that the joystick can respond. I am not sure if passing a handle to the Labview window would work because it is accessing the DLL's function? I tried passing LabView window handle to the function and read the X-axisposition off the joystick, but it read some junk (huge long integer) - which lead me to believe that the problem is something to do with initializing the joystick.
For all practical purposes, I am a complete novice at DirectInput
programming and working with Visual C++. Although, I have programmed in
C++previously. I am sorry for the long message, but I wanted to give a bit of background so that my aim is clear.
Any help, advice or direction with this problem be very much appreciated. Thank you for your time!
Cheers!
Abhishek

Hi,
This gave me the nudge in the right direction I needed, after a bit of basic frameset research I've got the desired functionality.
Huge thanks!

Similar Messages

Call a special function in the dll using Call Library Function Node????

Dear all,
I am calling a special function in the dll using call library function node. There is a input parameter that it is a enum type in this function. I don't know how to deal this parameter for calling this function.Has anybody solved this problem?Please advise!
I am appreciated of you anytime.

Most of the times an enum is just a U8/U16/U32, internally so probably you can call it with just a U8/U16/U32 or something. For the correct value you have to look at the definition.
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Can i use DLL file created by Fortran with the call libary function node

Can i use a DLL created by Fortran (Compaq Visual Fortran) with the call library function node in labview. If yes how do i create the DLL file if i have the Fortran code.
Thanks

Yes! Maybe these old post will help:
http://forums.ni.com/ni/board/message?board.id=170&message.id=88786
http://forums.ni.com/ni/board/message?board.id=170&message.id=109150
Good luck!
Message Edited by altenbach on 03-21-2006 02:35 PM
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DLL C/C++ syntax for Call Library Function Node

Hello,
I am interested in calling DLL from Labview and found several intersting tutorials on the Call Library Function Node. One interesting tutorial is Building a DLL with Visual C++ http://zone.ni.com/devzone/cda/tut/p/id/3056
One can notice in the example presented in this tutorial that the parameters that are outputs of the exported function are of type pointers. And I am curious about the theory behind this.
I looked also at the example in LabVIEW Call DLL.vi and it seems that all outputs are pointers to the desired data type.
I tried to write a short code where I assign a new value for one parameter in the export function. But this value is not updated in Labview. To make it clear: assume 50 is passed to an input parameter (on the left side of the Call Lib func Node). In the function, i assign 100 to this variable and expect this value on the output in Labview (right side indicator of Call Node) but the output remains 50.
I am trying to change my code but i get errors in linking (compiling is ok) that I cannot understand. LINK : fatal error LNK1168: cannot open Debug/DoseDLL.dll for writing
Error executing link.exe.
I don't get any error with the code provided in the above tutorial so i am trying to reproduce a similar code...
Thank you

Hello,
Please find attached the source code in C, the DLL and the vi.
you notice in the C code that I set variable dose=100 and this is the value I would like to export as an output for labview (right side of Node) for whatever value in the input (i put 50 for input dose). In the current code, the same value of input dose (50) is passed to the output (i assume it has to do with the reference ?). The idea is that variables dose and rate should be set/calculated in the DLL function.
Thank you!
Attachments:
DoseDLL3.cpp ‏1 KB
DoseDLL.vi ‏8 KB

LabVIEW PDA reports COREDLL.DLL error when using Call Library Function Node

I'm trying to build a LV PDA app that calls an external DLL file built using embedded visual C. When configuring the Call Library Function node I select the stub DLL, configure the I/O parameters and select OK. When the configuration dialog closes I get the following error:
LabVIEW: LabVIEW.exe - Unable to Locate Component
This application has failed to start because COREDLL.DLL was not found. Re-installing the application may fix this problem.
I do not get this error when using the configuration dialog in the example VIs.
Any suggestions as to the cause and/or the solution?
Thanks,
Ryan

Hello -
When you create a PDA VI that calls a DLL, you must include the .c or .lib file that corresponds to the DLL. Take a look at these documents:
LabVIEW PDA Module Build Errors with VIs that Call DLLs
Why Do I Receive Errors When Calling a C++ DLL from a Call Library Node Using the LabVIEW PDA Module...
How To Call External Code in LabVIEW PDA for Palm OS
H
ow To Call External Code in LabVIEW PDA for Pocket PC
Hope this helps!
S Vences
Applications Engineer
National Instruments

Help to make opencv's dll and LabVIEW's Call Library function node understanding each others

Hi, i have a little problem trying to use a C++ opencv's dll in labview. I wrote a really simple and stupid dll just to try to understand how it works the call library function node. Here the header code:
#ifdef GENERICDLL_EXPORTS
#define GENERICDLL_API __declspec(dllexport)
#else
#define GENERICDLL_API __declspec(dllimport)
#endif
#include "stdafx.h"
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <opencv/cv.h>
#include <opencv/highgui.h>
// Questa classe è esportata da Generic DLL.dll
class GENERICDLL_API CGenericDLL {
public:
int Summ(int a, int b);
int Sott(int a, int b);
int opencv(int a);
// TODO: aggiungere qui i metodi.
and here the .cpp:
// Generic DLL.cpp: definisce le funzioni esportate per l'applicazione DLL.
#include "stdafx.h"
#include "Generic DLL.h"
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <opencv/cv.h>
#include <opencv/highgui.h>
using namespace cv;
using namespace std;
// Esempio di variabile esportata
GENERICDLL_API int nGenericDLL=0;
// Funzioni esportate.
GENERICDLL_API int Summ(int a, int b)
return a+b;
GENERICDLL_API int Sott(int a, int b)
return a - b;
GENERICDLL_API int opencv(int a)
const string ind = "C:\\Users\\sviluppo\\Desktop\\Tuli.bmp";
const string ind_2 = "C:\\Users\\sviluppo\\Desktop\\Tuli_Gray.bmp";
//Mat image;
return 5;
i can call all the three simple functions in labview with this easy code. No problem at all. If i uncomment the line "Mat image;" the call library function node doesn't work and i receive the error:
"The library specified for this node cannot be found or cannot be loaded. Right-click the Call Library Function node and select Configure, then choose the correct library name or path."
I think that is a problem of dependencies between opencv libraries but i dont know how to manage this. Any ideas?
Thank you for yours time,
Francesco.

Hello Francesco,
I'm having exactly the same problem as you. I created a DLL that I can easily access from LabView. If I add one line and include "imgproc.hpp" (the only one I need), then LV gives me the same error you had. I read the thread Loura linked to, but I don't see how people actually take care of the dependecies (Klemen's examples did not work for me for the same reason, even though I recompiled the .cpp). Could you explain in detail what you did to make it work?
Thanks

When I use Call Library Function Node in real time, is the DLL loaded once for all or load every time it is called?

When I use Call Library Function Node in real time, is the DLL loaded once for all or load every time when it is called?
I have a time critical real time application, in which I use a piece of DLL function developed by C++. It is OK? Could any senior developer assure me?
Thank you in advance.
Solved!
Go to Solution.

qing_shan61 wrote:
When I use Call Library Function Node in real time, is the DLL loaded once for all or load every time when it is called?
Once
qing_shan61 wrote:
I have a time critical real time application, in which I use a piece of DLL function developed by C++. It is OK?
OK
Be sure that all DLL calls are thread safe (do not perform calls in UI thread).
Also for real-time application you need real-time OS.
Andrey.

Passing Variant to dll using call library function node

Hi,
Using LV2012
I have a dll that the following prototype:
SetTestResult(LPCTSTR Serial, int Test, int Result, VARIANT measuredValue);
How can I pass the Variant to this node when my variant can be either int or float.
I have tried "ToVariant" function but it is not sending data and gets error 1517 on LabView. For configuration parameters for variant I have used ActiveX type and datatype as activeX Variant Pointer.
So for call library function node my prototype looks like this:
int32_t SetTestResult(CStr Serial, int32_t Test, int32_t Result, VARIANT *measuredValue);
Can someone help me understanding What am I doing wrong here please?
Thank you,
Hiren
Hiren Patel

Hello Hiren,
Posting your code (even without the DLL) would definitely make it easier for people to point out potential issues. Here is an example that demonstrates passing an ActiveX variant to a DLL built in CVI, I would suggest cross-checking the way the Call Library Function Node has been configured.
Example:Transferring an ActiveX Reference Pointer to a CVI DLL
http://zone.ni.com/devzone/cda/epd/p/id/3343
Regards,
Tom L.

How to call a C pointer from call library function node

I have a client/server application which the client I am trying to develop using Labview. When I use to communicate the server and the client using the program provided by the manufacter, the system works perfectly.
Now, I am trying to develop a system using labview, because I need to get another things.
I have the DLL provided by the manufacter and the .h too, so I can check the functions parameters. One of these functions needs to be called using a struct element. Probably, the function's DLL instantiates the elements of this struct. I use the call library function node to do it.
When I receive the data, the function returns to me the struct that I passed as a parameter before, and then I can read all the elements of the struct, except the string element that returns nothing. The struct elements that are numerical, I can read them perfectly.
Another thing that is important to say, is that the string data was not returned in fact by the DLL function that the system calls. I have to pass a pointer (I use it as unsigned 16 in Labview, but I tried before as string and unsigned 8) as a parameter, and this pointer will point to the memory location that the string is. When I try to read what is returned by the function, I can read nothing. The same function returns that the size of data that is returning is 17 bytes.
How can I solve it?
Thank you in advance

Did you take a look at the example that ships with LabVIEW that shows how to do all sorts of data passing to DLLs. I believe your situation is one of the examples listed. You can find the example VI in the "<LabVIEW install directory>\examples\dll\data passing" directory.

Window doesn't close wheh Call Library Function Node set to Run in Any Thread

This is a problem regarding Call Library Function Nodes running in the UI thread or any thread.
I have a camera which has its own API supplied as a dll. I have created a set of VI wrappers which each call a function in the dll through a Call Library Function Node.
Initially each CLFN was set to 'Run in the UI thread' (the default).
To start the camera streaming images I call (through a CLFN)
ICubeSDK_Start(int CamIndex, Hwnd, ImgHandle, bool Preview, bool callback);
If Preview = True then the image is displayed in a preview window.
If ImgHandle = NULL a default preview window
is used.
In the CLFN definition I define:
ImgHandle as a U32
Preview as a I32
To stop the camera streaming images I call
ICubeSDK_Stop(int CamIndex)
In the actual implementation I set ImgHandle = 0 (NULL) and Preview = 1 (true).
This all works fine, and a preview window is opened and images displayed. When I call ICubeSDK_Stop the preview window is closed.
However, I would prefer to set the CLFN to 'Run in any thread' because
a) when run in the UI thread the preview window randomly gets sent to the back when I switch focus between open VI windows (presumably because it is in the same thread as the VIs)
b) I don't want to put unnecessary stuff in the UI thread
c) my (naive?) understanding is that it is safer to run in any thread
So I have set all CLFNs to 'Run in any thread'
When I do this the preview window opens OK, and behaves like any other non LabVIEW controlled window in terms of focus. But when I call ICubeSDK_Stop() the preview window does not get closed properly, it just shows a blank image. I can't close it manually, there is no X in the corner and no option to close it from the taskbar. To get rid of it I have to close the LabVIEW project it is spawned from, which often results in a crash. It does appear as a separate item in task manager but if I 'end process' it, LabVIEW closes (and often crashes) as well.
If I change only the CLFNs that call the Start and Stop functions back to 'Run in the UI thread' then it all works fine again, except that the preview window gets sent to the back randomly as before.
So, what do I have to do to get the preview window to close properly if I set the CLFN to 'Run in any thread'.
Alternatively, is there a way to close the window programmatically (ie force it to close) after I have called ICube_Stop.
Thanks
DAve

Hi Dave,
The "Run In UI Thread" switches from the thread the VIs currently executing in to the user interface thread. If you select "Run in Any Thread", the Call Library Function Node continues in the currently executing thread. By default, all Call Library Function Nodes run in the User Interface thread.
Before you configure the Call Library Function Node to run in any thread, you have to make sure that the code is thread safe. Code is thread safe when it does not store any global data (e.g. global variables, files on disks, etc.), does not access any hardware, does not make calls to any functions, libraries or drivers that are not thread safe.
Unfortunately, since you said that your DLL accesses hardware, it is not recommended to use "Run in Any Thread." This is probably why you are seeing the crash.
If your preview window gets sent to the back you can programmatically bring it forward. Here is an example of how this can be done: http://decibel.ni.com/content/docs/DOC-4551
If you want to completely close the window down you can do so as described in this link: http://digital.ni.com/public.nsf/allkb/81E9C1441900FFCE8625748F0055DBB0?OpenDocument
I also thought you might find this useful: http://zone.ni.com/devzone/cda/tut/p/id/3009
I hope this helps.
Regards,
Mahdieh G
Applications Engineer
National Instruments UK&Ireland

Call library function node in a loop

Hello All,
I am currently using a call library function node in a while loop which calls a third party dll to process and recieve some data.
My question is, if I am using this function in a while loop, what exactly happens?
Does the dll get called in each loop iteration, or does it keep the called dll loaded in memory and just pass the values to it to process data?
Also, if the answer to the above question is that it will make calls to the DLL in each iteration, how can we keep it loaded in memory always? I mean, if the DLL is a .NET application DLL, I believe the main .NET application which uses this DLL won't do multiple calls to the dll, rather it will keep it loaded in memory.
Thanks
FraggerFox!
-FraggerFox!
Certified LabVIEW Architect, Certified TestStand Developer
"What you think today is what you live tomorrow"

Hi,
the DLL will stay in memory as long as there is a program running which has not closed (unloaded) the DLL.
Doing repetitive calls to the DLL is irrelevant in this context. LV opens the DLL as soon as needed and will only unload it when there is no VI in memory which has a CLN to that DLL...
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Call library function node with array of clusters using array data pointer

Hello all.
I am writing a LabVIEW wrapper for an existing DLL function.
The function has, as one of its parameters, an array of structs. The struct is very simple, containing two integers. I am using the call library function node to access it.
In Labview I created an array of clusters, where the cluster has two 32-bit integers as its members. So far, so good.
Now I have to pass this in to the Call Library Function Node. Here I am running into trouble.
I have used The topic in LAVA and The topic in the knowledge base as my primary sources of information, though I have read a bunch of forum topics on the subject too.
I do understand that I could write a new function which takes as a parameter a struct with the size as the first member and an array as the second, and I might just do this and have it call the regular function, but I was hoping to do it more simply.
According to the C file which LabVIEW generates for me from the CLFN when I choose "Adapt to Type" and "Array Data Pointer", the prototype it is expecting is:
int32_t myFunc(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, void data[], int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex);
And the prototype of the function in my DLL is
int borland_dll myFunc(DWORD handle, usint channel,
int FIFOnumber, struct mStruct *data, int numWords, int *actualLoaded, int *actualStartIndex);
This looks like a match to me, but it doesn't work (I get garbage in data). From the topic in LAVA referenced above, I understood that it would work. It does not.
If I cast data to the pointer-to-pointer I get when I generate c code by wiring my struct to a CIN and generating, then I seem to get what I expect. But this seems to work when I choose "pointers to handles" too, and I would expect array data pointer to give a different result.
Is there any way to get this to work directly, or will I have to create a wrapper? (I am currently using LabVIEW 2011, but we have customers using 2009 and 2012, if not other versions as well).
Thank you.
Batya
Solved!
Go to Solution.

OK, here is more detailed information.
I have attached the VI.
This is the code from the "C" file created by right-clicking the CLN and creating a "C" file.
When the parameter in the CLN is set to "array data pointer":
/* Call Library source file */
#include "extcode.h"
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, void data[], int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex);
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, void data[], int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex)
/* Insert code here */
When the parameter is "pointers to handles":
/* Call Library source file */
#include "extcode.h"
/* lv_prolog.h and lv_epilog.h set up the correct alignment for LabVIEW data. */
#include "lv_prolog.h"
/* Typedefs */
typedef struct {
int32_t control;
int32_t data;
} TD2;
typedef struct {
int32_t dimSize;
TD2 data[1];
} TD1;
typedef TD1 **TD1Hdl;
#include "lv_epilog.h"
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, TD1Hdl *data, int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex);
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, TD1Hdl *data, int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex)
/* Insert code here */
When the parameter is set to "handles by value":
/* Call Library source file */
#include "extcode.h"
/* lv_prolog.h and lv_epilog.h set up the correct alignment for LabVIEW data. */
#include "lv_prolog.h"
/* Typedefs */
typedef struct {
int32_t control;
int32_t data;
} TD2;
typedef struct {
int32_t dimSize;
TD2 data[1];
} TD1;
typedef TD1 **TD1Hdl;
#include "lv_epilog.h"
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, TD1Hdl *data, int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex);
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, TD1Hdl *data, int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex)
/* Insert code here */
As to the DLL function, it is a bit more complicated than I explained above, in the current case. My VI calls the function by this name in one DLL, and that DLL loads a DLL and calls a function (with the same name) in the second DLL, which does the work. (Thanks Rolfk, for helping me with that one some time back!)
Here is the code in the first ("dispatcher") DLL:
int borland_dll Load_Transmit_FIFO_RTx(DWORD handle, usint channel, int FIFOnumber, struct FIFO_DATA_CONTROL *data, int numWords, int *actualLoaded, int *actualStartIndex)
t_DispatchTable *pDispatchTable = (t_DispatchTable *) handle;
int retStat = 0;
retStat = mCheckDispatchTable(pDispatchTable);
if (retStat < 0)
return retStat;
if (pDispatchTable->pLoad_Transmit_FIFO_RTx == NULL)
return edispatchercantfindfunction;
return pDispatchTable->pLoad_Transmit_FIFO_RTx(pDispatchTable->handlertx, channel, FIFOnumber, data, numWords, actualLoaded, actualStartIndex);
borland_dll is just "__declspec(dllexport)"
The current code in the DLL that does the work is:
// TEMP
typedef struct {
int control;
int data;
} TD2;
typedef struct {
int dimSize;
TD2 data[1];
} TD1;
typedef TD1 **TD1Hdl;
// END TEMP
int borland_dll Load_Transmit_FIFO_RTx(int handlertx, usint channel, int FIFOnumber, struct FIFO_DATA_CONTROL *data, int numWords, int *actualLoaded, int *actualStartIndex){
struct TRANSMIT_FIFO *ptxFIFO; //pointer to transmit FIFO structure
usint *pFIFOlist; //pointer to array of FIFO pointers to FIFO structures
int FIFOentry, numLoaded;
usint *lclData;
usint nextEntryToTransmit;
// TEMP
FILE *pFile;
int i;
TD1** ppTD = (TD1**) data;
TD1 *pTD = *ppTD;
pFile = fopen("LoadFIFOLog.txt", "w");
fprintf(pFile, "Starting Load FIFO with %d data words, data pointer 0x%x, with the following data&colon; \n", numWords, data);
for (i = 0; i < numWords; i++) {
fprintf(pFile, "%d: control--0x%x, data--0x%x \n", i, data[i].control, data[i].data);
fflush(pFile);
fprintf(pFile, "OK, using CIN generated structures: dimSize %d, with the following data&colon; \n", pTD->dimSize);
for (i = 0; i < numWords; i++) {
fprintf(pFile, "%d: control--0x%x, data--0x%x \n", i, pTD->data[i].control, pTD->data[i].data);
fflush(pFile);
// END TEMP
if ((handlertx) <0 || (handlertx >= NUMCARDS)) return ebadhandle;
if (cardrtx[handlertx].allocated != 1) return ebadhandle;
pFIFOlist = (usint *) (cardrtx[handlertx].segaddr + cardrtx[handlertx].glob->dpchn[channel].tr_stk_ptr);
pFIFOlist += FIFOnumber;
ptxFIFO = (struct TRANSMIT_FIFO *)(cardrtx[handlertx].segaddr + *pFIFOlist);
//use local copy of ptxFIFO->nextEntryToTransmit to simplify algorithm
nextEntryToTransmit = ptxFIFO->nextEntryToTransmit;
//on entering this routine nextEntryToLoad is set to the entry following the last entry loaded
//this is what we need to load now unless it's at the end of the FIFO in which case we need to wrap around
if ( ptxFIFO->nextEntryToLoad >= ptxFIFO->numEntries)
*actualStartIndex = 0;
else
*actualStartIndex = ptxFIFO->nextEntryToLoad;
//if nextEntryToLoad points to the last entry in the FIFO and nextEntryToTransmit points to the first, the FIFO is full
//also if nextEntryToLoad == nextEntryToTransmit the FIFO is full and we exit without loading anything
if (( (( ptxFIFO->nextEntryToLoad >= ptxFIFO->numEntries) && (nextEntryToTransmit == 0)) ||
( ptxFIFO->nextEntryToLoad == nextEntryToTransmit)) && (ptxFIFO->nextEntryToLoad != INITIAL_ENTRY)){
*actualLoaded = 0; //FIFO is full already, we can't add anything
return 0; //this is not a failure, we just have nothing to do, this is indicated in actualLoaded
numLoaded = 0;
lclData = (usint *)data; //must use 16 bit writes to the module
//conditions are dealt with inside the for loop rather than in the for statement itself
for (FIFOentry = *actualStartIndex; ; FIFOentry++) {
//if we reached the end of the FIFO
//if the module is about to transmit the first element of the FIFO, the FIFO is full and we're done
//OR if the module is about to transmit the element we're about to fill in, we're done - the
//exception is if this is the first element we're filling in which means the FIFO is empty
if ((( FIFOentry >= ptxFIFO->numEntries) && (nextEntryToTransmit == 0)) ||
((FIFOentry == nextEntryToTransmit) && (FIFOentry != *actualStartIndex) )){
*actualLoaded = numLoaded;
//set nextEntryToLoad to the end of the FIFO, we'll set it to the beginning next time
//this allows us to distinguish between full and empty: nextEntryToLoad == nextEntryToTransmit means empty
ptxFIFO->nextEntryToLoad = FIFOentry;
return 0;
//we reached the end but can continue loading from the top of the FIFO
if ( FIFOentry >= ptxFIFO->numEntries)
FIFOentry = 0;
//load the control word
ptxFIFO->FifoData[FIFOentry * 3] = *lclData++;
//skip the high of the control word, the module only has a 16 bit field for control
lclData++;
//now put in the data
ptxFIFO->FifoData[(FIFOentry * 3) + 2] = *lclData++;
ptxFIFO->FifoData[(FIFOentry * 3) + 1] = *lclData++;
numLoaded++;
//we're done because we loaded everything the user asked for
if (numLoaded >= numWords) {
*actualLoaded = numLoaded;
ptxFIFO->nextEntryToLoad = FIFOentry+1;
return 0;
//if we reached here, we're done because the FIFO is full
*actualLoaded = numLoaded;
ptxFIFO->nextEntryToLoad = FIFOentry;
fclose (pFile);
return 0;
As you can see, I added a temporary diagnostic with the structures that were created in the "Handles by value" case, and print out the data. I see what is expected, whichever of the options I pick in the CLN!
I understood (from the information in the two links I mentioned in my original post, and from the name of the option itself) that "array data pointer" should pass the array of data itself, without the dimSize field. But that does not seem to be what is happening.
Batya
Attachments:
ExcM4k Load Transmit FIFO.vi ‏15 KB

How to implement a callback function using LabView's Call Library Function Node?

I am trying to call a fuction from a SDK.dll library using the Call Library Function Node. The SDK was provided to
me and I do not have the source code, just the .dll and .h files.
The SdkSetPropertyEventHandler function has a callback fuction as one of its parameters. How do I implement the
callback using the CLF node? I am a good LabView programmer but this is my first time using the Call Library
Function Node. I have read all the info I can find on NI's web site and the discussion board but cannot figure
this one out. I am using LabView 8.6.
The SDK.h deacribes the function as:
// Function:   SdkSetPropertyEventHandler
SdkError SDKAPI SdkSetPropertyEventHandler(
            SdkCameraRef                    inCameraRef,
            SdkPropertyEvent                inEvnet,
            SdkPropertyEventHandler         inPropertyEventHandler,
            SdkVoid*                        inContext );
// Description:
//       Registers a callback function for receiving status
//          change notification events for property states on a camera.
// Parameters:
//       In:    inCameraRef - Designate the camera object.
//              inEvent - Designate one or all events to be supplemented.
//              inPropertyEventHandler - Designate the pointer to the callback
//                      function for receiving property-related camera events.
//              inContext - Designate application information to be passed by
//                      means of the callback function. Any data needed for
//                      your application can be passed.
//      Out:    None
// Returns:    Any of the sdk errors.
A separate header file called SDKTypes.h contains the following data:
typedef SdkUInt32 SdkPropertyEvent;
typedef SdkUInt32 SdkPropertyID;
typedef void       SdkVoid;
typedef struct __SdkObject*    SdkBaseRef;
typedef SdkBaseRef    SdkCameraRef;
SdkPropertyEventHandler
typedef SdkError ( SDKCALLBACK *SdkPropertyEventHandler )(
                    SdkPropertyEvent        inEvent,
                    SdkPropertyID           inPropertyID,
                    SdkUInt32               inParam,
                    SdkVoid *               inContext );
Thanks for your help.
Alejandro
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Go to Solution.

alejandroandreatta wrote:
I am trying to call a fuction from a SDK.dll library using the Call Library Function Node. The SDK was provided to
me and I do not have the source code, just the .dll and .h files.
The SdkSetPropertyEventHandler function has a callback fuction as one of its parameters. How do I implement the
callback using the CLF node? I am a good LabView programmer but this is my first time using the Call Library
Function Node. I have read all the info I can find on NI's web site and the discussion board but cannot figure
this one out. I am using LabView 8.6.
Basically you do not do that. LabVIEW does not know pointers and certainly not function pointers. What you should do instead is writing a C DLL that implements the callback and also exports a function to be called by LabVIEW that translates between the callback and a LabVIEW user event. Look for PostLVUserEvent() here on the NI site to find examples how to do that.
Rolf Kalbermatter
Message Edited by rolfk on 02-11-2009 08:00 PM
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Execution time for Call Library Function Node

I am experimenting with the Call Library Function Node block in LabVIEW and am curious if it should be running faster than what I'm seeing. For testing purposes, I have compiled and transfered to my RT target the .out file from the KB article http://digital.ni.com/public.nsf/allkb/81D1172E3C28A5E4862575CC0076A230 (I'm using the vxworks 6.1 version). The function in the .out file just multiplies two inputs together, adds a constant, and returns the result. I have put this inside a 1 kHz timed loop with a commanded period of 1 ms and via the Ticks(ms) block and shift registers I calculate the amount of time per loop execution. This process is apparently taking 5 ms per cycle and to me that seems slow. Is that roughly the correct execution time for this kind of setup? I will attach my test .vi file.
What I'm using:
Windows 7
LabVIEW 2009 SP1
NI-cRIO 9024 with NI-RIO 3.4.0
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Attachments:
test DLL.vi ‏31 KB

First off, the way you are doing timing isn't necessarily accurate because you don't know when the tick count VI is being called. For example, if it gets called on one iteration after your call library node executes, and the next iteration it gets called before the CLFN it executes, the subtraction doesn't include the call of the CLFN so you aren't seeing the true time it is taking for the dll to be called.
Where it says "error" on the top left hand corner of your loop. left click and choose previous iteration timing. Also, do you have the ability to choose a 1 Mhz clock? Are you sure it's actually being run on the RT and not on your PC? Running it on the PC would definitely make it difficult to execute at a 1 kHz rate.
CLA, LabVIEW Versions 2010-2013

Call Library Function Node not Supported

Hai,
I have question to ask to NI members. I get an error said " Call Library Function Node 'LVASPT_WA.*ptDecimationFilterH':Node not supported". I use the call library function node in the FPGA.VI in my design. My question is, is it the function cannot used in FPGA.VI? I try to search a similar thread and find the manual but still can't find the answer. Anyone please clarify it to me. Thanks in advance.

You cannot use Call Library Function Node in FPGA. The FPGA is hardware - it has no way to call an external library. If it is not immediately obvious why it's impossible for the FPGA to call a DLL, you should spend some time understanding what a FPGA is.
You can integrate FPGA code written outside the LabVIEW environment, but that's not the same as calling a DLL.

Calling a Function node in a DLL to give force-feedback effect to a joystick (using DirectInput)

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