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
Solved!
Go to Solution.
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

Similar Messages

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

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.

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.

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!
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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
Solved!
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

Strange problem of calling library function node in labview 2010 and 2011

one year ago,I develop a program to usb device data and it works well,in labview 8.6 or 2009(win xp).Recently, When I test
the program in labview 2010 and labview 2011(win xp).,the program always crash immediately.I check the program and find main
problem is in call library function node. In my program,I use labview 2009 library for the USBExpress driver for
Silicon Labs USB MCU's from:https://decibel.ni.com/content/docs/DOC-9522,for example, 2 functions SI_OPEN and SI_READ
can not work well.
the header definition of SI_OPEN and SI_READ is:
SI_STATUS WINAPI SI_Open(
DWORD dwDevice,
HANDLE* cyHandle
SI_STATUS WINAPI SI_Read(
HANDLE cyHandle,
LPVOID lpBuffer,
DWORD dwBytesToRead,
LPDWORD lpdwBytesReturned,
OVERLAPPED* o = NULL
the SI_STATUS is equivalent to int type.
orignally, for HANDLE * in SI_Open, the parameter type in call library function node is numeric, data format is unsigned 32 bit integer ,and pass pointer to value.
for HANDLE in SI_Read, the parameter type in call library function node is numeric, data format is unsigned 32 bit integer ,and pass value.The program works well in labview 8.6&2009,however,crash in labview 2010 &2011.
later,I debug the program, for HANDLE *, I choose parameter type in call library function node as adapt to type, data format is point to Handles.for HANDLE, I choose parameter type in call library function node as adapt to type, data format is Handles by Value.Crash not happend in labview 2010&2011,however,it cannot read any data from from USB device correctly as before.I can not find the reason.
Dear friends,I need your help to answer the problem. Thank you.

Based on the help page it looks like it should execute asynchronously.
The thing in the description that leads me to believe they execute asynchronously is that you can configure the library to run as a multi-threaded operation.
Please take a look here to see the difference between synchronous and asynchronous execution.
Since the code even has the ability to be multi-threaded, you can consider it as running in parallel to your other code.
Any data returned is passed to the thread that called that function.
Cory K

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.
Ton
Free Code Capture Tool! Version 2.1.3 with comments, web-upload, back-save and snippets!
Nederlandse LabVIEW user groep www.lvug.nl
My LabVIEW Ideas
LabVIEW, programming like it should be!

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.

DIO Port Config & DIO Port Write Block Diagram Errors (Call Library Function Node:library not found or failed to load)

Hi Guys, need help on this.
I have this LabVIEW program that used to work on the old computer.
The old computer crashes most of the time, so I upgraded the computer
and used its Hard Drive as slave to the new computer.
I have no idea where are its installers since the guy that made the program
is not in my department anymore.
I downloaded all the drivers needed from NI: NIDAQ9.0, NIVISA,NI488.2,
and drivers of some instruments needed in the setup. I'm using LabVIEW8.2.
Everything's fine until I open the LabVIEW program for our testing.
Here goes the error:
   DIO Port Config
   DIO Port Write
Block Diagram Errors
   Call Library Function Node: library not found or failed to load
Attachments:
ErrorList.JPG ‏200 KB

Honestly, I'm a newbie on Labview. I just want this old program to run on the new computer.
The guys that installed the drivers on the old computer are no longer here in my department.
And I have no idea where the drivers are. So I just downloaded the drivers needed for my hardware and instruments.
Here's my hardware: (cards: PCI-DIO-96, PCI-GPIB), (instruments: SCB100,E4407B, HP83623, HP3458, HP8657)
OS: Windows XP Pro
By the way, I have unzipped the TraditionalDAQ drivers. First I tried the 7.4.1, but installation error appeared.
I thought maybe the installer is corrupted, so I downloaded the 7.4.4 and unzipped it.
But, still same installation error appears. I don't understand, both TraditionalDAQ drivers have same installation error.
Now I have tried the DAQmx8.7.2 driver, bu still the DIO Port Config and DIO Port Write have errors.

Call Library Function Node: library not found or failed to load

Hello,
I had a VI that could not find some of the dll functions it needed. It works on one machine and not on another. So foolishly I copied the dll in question from the working machine and pasted it over the one on the non-working machine.
Now all my math functions are broken on the machine I copied the dll too. The error is "Call Library Function Node: library not found or failed to load"
And if I try to relink in the VI I get "Error loading C:\National Instruments\LabVIEW 8.2\resource\lvanlys.dll" A dynamic link library (DLL) initialization routine failed."
I tried a repair labview and that did not help.
I tried uninstall and reinstall labview and that did not help!
Please help me fix this!
Version 8.2
dll: C:\National Instruments\LabVIEW 8.2\resource\lvanlys.dll
Jim

What library did you first copy?
Also lvanlys.dll depends on the Intel Math Kernel Library that gets installed in a different location "C:\Program Files\National Instruments\Shared\MKL".
This Intel Math Kernel Library again depends on the Visual C runtime libraries. Most likely you replaced one of those runtime libraries somehow and now the Math Kernel Library (MKL) fails to initialize which causes thelvanlys.dll to fail its load.
Without a good view on your system and what other NI software you have installed it is very hard to recommend a good way of proceeding. There are various versions of the MKL used by various versions of NI products and just deleting the entire MKL folder might get you into trouble with other NI tools.
Deinstalling everything from NI, deleting the entire National Instruments folder and then reinstalling what you need would be the most safe proceeding.
And next time don't just copy some Visual C runtime libraries between machines. Their dependencies are complicated at the least and simply not graspable by us mere mortals. Use the according C runtime installer for the version you need as that installer will take care of installing the right versions of C runtime components and registering everything proberly so you do not usually run into problems with other applications using different versions of the C runtime.
Message Edited by rolfk on 03-01-2010 10:26 AM
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

VI analyzer: Wire under object test fails with Call Library Function Nodes

Hi,
If I wire a Call Library Function Node with an ErrorIn and an ErrorOut, the VI Analyzer Test "Wire under Object" fails always with two occurrences per Call Library Function Node.
A double click to the occurrence highlights the error lines connected with the call... node.
The test does not fail, if the error lines are not connected.
Thanks!
H
Solved!
Go to Solution.

This became a problem when Call Library Nodes got error terminals (and optional path terminals) in LabVIEW 8.20. I should be able to get a fix in to VI Analyzer Toolkit 2010.
Thanks for taking the time to report the bug.
Darren Nattinger, CLA
LabVIEW Artisan and Nugget Penman

Is a call library function node in LabView 8.6 synchronous or asynchronous?

I tried setting a sub-VI with a call library function node in it to "subroutine" execution status. The error list indicated that the Call Library Function node in the block diagram was an asynchronous node. The LabView on-line help content indicates
"...CINs and shared libraries execute synchronously, so LabVIEW cannot use the execution thread used by these objects for any other tasks. "
Does anyone know for sure what the status of a Call Library Function is? Does it depend upon the specific code in the DLL being called?
Thanks,
Mike H.

Based on the help page it looks like it should execute asynchronously.
The thing in the description that leads me to believe they execute asynchronously is that you can configure the library to run as a multi-threaded operation.
Please take a look here to see the difference between synchronous and asynchronous execution.
Since the code even has the ability to be multi-threaded, you can consider it as running in parallel to your other code.
Any data returned is passed to the thread that called that function.
Cory K

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

[HELP] Call Library Function Node...

I have a DLL which has a function as follows:
int GetMessageNameNumber (char* messageName [], const int MessageNumber);
The function is used thus:
char *MessageName = NULL;
int MessageNumber = 0;
error = HL1553API_GetMessageNumberName (&MessageName, MessageNumber);
MessageName will then contain the message name as a string.
I having the devils own job trying to wrap this into a Labview module. I have a Call Library function node for the above function, but I am not sure what to set the "MessageName" parameter too! I have tried Array of signed 8-bit integers, Adapt to Type, Array Data Pointer and then passed in a String array. Whatever I do results in LabView crashing. I know HL1553API_GetMessageNumberName works, because if I call it directly in TestStand it works fine. I need it LabView though!
Any ideas?
Christopher Povey
Senior Test Systems Engineer for BAE Systems.
Solved!
Go to Solution.

In C a pointer to a string or an array of strings are completely ambigues.
char ** something ===== char * something [].
You can not tell the two apart from the syntax but only from the documentation or from an example showing how the function is called. A C compiler treats the two equal in terms of access (but a C++ compiler will make a syntactic distinguishment when syntax checking code, resulting in possible compile warnings when prompted to use a sufficiently high warning level.)
The sample shows that this is not an array of strings that gets allocated by the caller and passed to the function, but a string pointer that gets passed by reference. As such the function will allocate a pointer and return it (a highly non-standard C practice at least for strings). This automatically begs the question when and how will this pointer be deallocated? The documentation for that function should document the memory manager call used to allocate that pointer and also point out the function to call to deallocate it. Ideally the library (DLL) provides a specific exported function for that purpose.
Assuming everything I have talked about so far is clear and available you have to trick LabVIEW a bit. You have to configer a pointer sized integer that gets passed by reference. Now this integer in the diagram IS in fact your string. If you only need to pass this pointer to other Call Library functions you are already done. Otherwise if you need to access the contents of that string from the LabVIEW diagram, you have to copy the information of that string pointer into a real LabVIEW string.
One way to do that is to use the MoveBlock() C function export that LabVIEW exports itself. I have explained this several times here on this forum and a search for MoveBlock will without doubt uncover those posts.
Another slightly better way is to use the LStrPrintf() function that LabVIEW also exports. For that you configure a Call Library function as follows:
Library name: LabVIEW
Function name: LStrPrintf
Calling convention: C
Threading: both are possible but the function is thread safe so just use reentrant
return parameter: int32 (this is a possible LabVIEW manager error code)
1st parameter: LabVIEW string handle, passed by value
2nd parameter: C string pointer
3rd parameter: pointer sized integer, passed by valu
Wire an empty string constant to the first parameter.
Wire a constant containing the text "%s" without quotes to the 2nd.
Wire your string pointer to the 3rd
On return the function will either return 0 as return value and the contents of the string on the output side of the 1st parameter or a non-zero return value indicating an error.
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Execution time for Call Library Function Node

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