Where is pointer pointing to in Call Library Function

I am using Call Library Function (FillString) to call a function in a DLL. I set Parameter 1 to:
Parameter: arg1
Type: Array
Data Type: signed 32-bit Integer
Dimension : 1
Array Format: Array Data Pointer
so the Function Prototype below in the Call Library Function dialogbox is written as:
void FillString(long *arg1);
At the same time, in the block diagram , there is a "input param" (array of int32) and "output param" (array of int 32)
I wonder, when the program is in the DLL FillString function and using arg1 pointer, does "arg1" point to the data in "input param" arry or the data in "output param" array? I don't quite understand, since normally C programs have only one return value, while the Call Library Function returns a value for every input parameter. Is the "output param" a different variable, or the same as "input param" (i.e., the same physical memory address)?

Hi LyLee,
if you know how many elements you need, create an array with this number of elements by using the "initialize array" function and connect it to your dll node. The output shall contain your data. If you have a string its the same. Create an empty string with the size you need. See the attached example picture.
Mike
Attachments:
Unbenannt.PNG ‏3 KB

Similar Messages

Pointer to struct in call library function

I have a dll function with this prototype:
DWORD CAN_Read(TPCANMsg* pMsgBuff);
where TPCANMsg is a structure.
typedef struct{
DWORD ID;
BYTE MSGTYPE;
BYTE LEN;
BYTE DATA[8];
}TPCANMsg;
I create a cluster that is represented as a structure. But in Call Library Function witch do I have to choose: "Handles by Value" or "Pointers to Handles"?

> I have a dll function with this prototype:
> DWORD CAN_Read(TPCANMsg* pMsgBuff);
> where TPCANMsg is a structure.
> typedef struct{
> DWORD ID;
> BYTE MSGTYPE;
> BYTE LEN;
> BYTE DATA[8];
> }TPCANMsg;
> I create a cluster that is represented as a structure. But in Call
> Library Function witch do I have to choose: "Handles by Value" or
> "Pointers to Handles"?
The key is to make sure the type is set to Adapt. The setting of the
Data Format shouldn't matter since your datatype doesn't have a string,
array, path, or other nonflat data element.
for the DATA[8], you will want to use eight inline U8s, or a cluster of
the bytes.
The info I'm going on is the LV External Code manual.
Greg Mckaskle

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.

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 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.

Call Library function

Hi,
I just transfered some of my programs (in LV5.0 - student edition) from one computer to another. The programs work perfectly on computer A, but when I transfered them to computer B, an error comes up saying 'call library function not supported in this version'. What I don't understand is that I am using the exact same LV5.0 student edition on both computers - was maybe an update installed on the original computer to allow the call library function to work? If so, where could I find this? Any other ideas why I can't use Call Library Function on computer B?

Hi LV newbie,
Th call library function calls functions within a dll. The dll can be an API or driver from the equipment manufacturer or custom-made functions to control or communicate with the DUT.
So the first thing I would look for is the dll in question.
When you transferred the LV code from computer A to B, did you do a mass compile? (Tools > Advanced > Mass Compile). You can try that. If already done that, open the vi giving you trouble and look at the call library function. Is it pointing to the right directory to find the dll? The problem may be in the ability for the vi to find the dll. Make sure it is calling the right function(s) and passing the appropriate parameters and values. Strange things can happen when moving LV from one PC to
another.
Let us know your progress.
JLV

Passing arrays with Call Library Function does not work after application builder

Calling a DLL with Call Library Function which requires an array of data works correctly in Labview, but after building an exe with application builder, the call no longer works. Dereferecing the pointer in the DLL retuns all 0s and not the actual values.
Solved!
Go to Solution.
Attachments:
TEST.zip ‏28 KB

I did not run your code because it is a little unclear to me what it does.
Two things:
First, is the DLL you are calling the DLL-ified version of PopUpNames.vi? Then the problem is likely that the panel is not being built into the DLL.
When LabView builds an application / dll, it strips the front panel and block diagram from all VIs that it doesn't think need to show a panel at run time. This reduces file size and increases code security. The App Builder's panel inclusion logic can be overridden by Build Specifications -> Source File Settings -> Remove front panel. A better method is to put a property node on a control in a window you want to show marking it "visible"; this is sufficient to tell the App Builder it should keep the panel.
Currently Source File Settings shows "no dependencies" (clearly incorrect---another evil side effect of Express VIs I guess) but if you change the settings as shown below to keep ALL panels, one might hope the App Builder can figure it to keep the panel when it deconstructs the Express VI. (Alternatively convert the Express VI into a regular one.)
A second comment: I am a bit flummoxed at the larger goal here. You are calling LabView DLL from LabView, which doesn't make a lot of sense, so I assume your larger goal is to call LabView from C or vice-versa. In that case be aware that your DLL is x86 (32-bit) but you are passing 64-bit ints as your pointers. In this case it is 32-bit LabView with 32-bit pointers in embedeed in 64-bit containers calling 32-bit LabView with 32-bit pointers in embedeed in 64-bit containers, so it all works, but if your going to call this from C or whatnot you're going to have to follow that same design.
When calling C code the LabView Call Library Function does have a "unsigned pointer-sized integer" data type that always appears to be 64 bits in the dev env but which actually passes a 64 or 32-bit int to the DLL depending on the environment. The "pointer sized int" has to be 64 bits in the "LabView" part of the code because LabView's strong typing requires the data type to be determined at compile time. Casting all pointers to the largest data type in LabView makes it possible to write platform-independent code, but down at the Call Library level you still have to put the right number of bytes on the stack.

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 library function inside a conditional disable bug

i'm trying to call a function in a dll using the call library function inside a conditional disable structure.
one of the parameters is a pointer to a C structure.
here is the prototype:
short in myfunction(short in DevNum, void *pMetrics);
outside of the conditional disable, LabVIEW allows me to wire the pMetrics parameter to a cluster.
if i put the function inside the conditional disable, LabVIEW doesn't allow me to wire it.
as a workaround, i put the cluster inside the conditional disable as well.
any ideas?

Simply create a constant of the cluster and and put it outside the disable structure. Wire this constant to all inputs (left side terminal) of the Call Library Node. A Call Library Node (CLN) set to Adapt to Type does need a valid datatype to adapt too. This works from the outside side (right side terminal) of the CLN only if the according indicator is inside the same data structure. In older LabVIEW versions you actually had to always define the left side by wiring a constant or a dummy control to it.
This has to do with the algorithme that evaluates datatypes along wires. Making that algorithme go backwards (against the natural dataflow) inside one subdiagram without causing circular references or similar is already a challange. Doing that across diagram boundaries (case, disable, loop, etc. structures) is basically impossible without causing the entire edit operation to get very slow.
Message Edited by rolfk on 10-20-2009 08:28 AM
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

The call library function require us to define the type of parameter that w are using.The type of parameter in cludes numeric, array, string,waveform and adapt to type.I would like to know more about waveform and adapt to type.

In the labview manual, there is very little mention about the use of waveform.How is this waveform being called and can i have an example to see how this work.
Also in the adapt to type paramete, what does this parameter do and in what circumstances do we need to use it.The manual say something about the use of this parametr.It says that scalar elements in arrays or clusters are in line.For example a cluster containing anumeric is passed as pointer to a structure containing a numeric. What does this statement mean?
Can i imply t
hat if my input is a struct, can i use a adapt to type parameter to overcome this incompatibility?Can i also have an example to let me have a better idea.thank you

I'm going to share my experience with the "Adapt to Type" parameter.
Attached to this message is an example. The attachment is a zip file with three files: a dll, a c file and a vi written in LabVIEW 6. The dll contains a function that return a structure with 3 values (like the coordinates of a point in space, that is, (x, y, z)). You can see how the function was constructed by looking at the c file.
In LabVIEW, I created a cluster with the same three parameters. Then, I configured the call library function following the function prototype as in the c file. For the point variable I use "Adapt to Type".
I hope this can give you a head star.
Best regards;
E. Vargas
www.vartortech.com
Attachments:
pointexample.zip ‏63 KB

Call Library Function Node.vi using problem

Hi,
我用Labwindows 编了个读文件的程序然后生成动态库, 然后在LabVIEW里调用该动态库(Call Library Function Node), 即向该动态库传递文件名及路径和某一字符串,然后该动态库打开相应路径文件从中读出并返回三个参数值,可是每次的返回值总显示打开文件失败, 该函数在Labwindow里没有问题. 在LabVIEW里如何调试来确定传到动态库的参数格式是没有问题的呢?任何的指点迷津,不胜感激!
Frank,

xiejiezhou wrote:
Thank Georges and Rolf Kalbermatter,
I changed the runtime support with " Full Runtime Engine" instead of " LabVIEW Real-Time Only" before, it's work now, but the output parameters returned are irregular incorrect characters. My funciton prototype is:
DLLEXPORT long CollectParameter(char *NomFile, char *szNomParagraph, char *Command[], char *Type[], char *Value[])
so how to configure the type in LabVIEW respectively? I tried every types, just "c String Pointer" is ok, but returned value irregular & incorrect.
As Geogre's suggestion, i should add my code as below function generated by LabVIEW, is it?
ong CollectLabel(char szNomFile[], char szNomParagraph[], char Command[], char Type[], char Value[])
/* Insert code here */
Frank
The char *Command[], char *Type[], char *Value[] parameters are parameters that you can not create with LabVIEW. This are arrays of strings and and LabVIEW has a completely different idea about how to place strings and arrays in memory than what is used in C.
And while LabVIEW supports translation of the top level type to C compatible pointers it does not have any option to let you configure it to translate embedded elements in parameters (the strings in the array) to be translated too.
But to be honest what you seem want to do is read in a file, do some parsing and then return parameters taken out of that file. Doing that all in LabVIEW would be SOOOOOOOOOOOO much easier.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Using an external DLL with "Call Library Function"

Hi!
I am trying to use an external DLL which is used from Visualbasic & Delphi:
http://www.keb.de/common/tools/KEBCOMDriver.zip
the protKEB.dll accesses the serial port to control an KEB frequency
inverter.
Unfortunatly there is no prototype header file for the DLL (no help on that
from KEB).
I only have a VisualBasic example program which works with the DLL.
(Unfortunatly I am no Visual basic expert)
To initialize the com port I have to use the function: setprotproperties &
getprotproperties
they are declared as:
'Setting the protocol properties
'ctrl is a pointer to a data structure of type tProtProperty
Declare Sub setprotproperties Lib "protkeb.DLL" (ctrl As Any)
'Reading the protocol properties
'ctrl is a pointer to a data structure of type tProtProperty
'the desired protocol is entered in ctrl.prottype before calling
Declare Sub getprotproperties Lib "protkeb.DLL" (ctrl As Any)
and tProtProperty is:
Public Type tProtProperty
ProtType As Long 'Type of Protocol (tProt)
TimeOut As Long 'ALL protocols
Baudrate As Long 'ANSI, HSP5
Comport As Long 'ANSI, HSP5
Flag As Long 'ANSI, HSP5: 01 = Sendslow
/ IP: 01 = UDP
Port As Long 'IPort number
Txtlen As Byte 'IP : length of following
text or 0
txt As String * 100 'IP : IP-Address or name
(maximum length)
End Type
I already tried to use a cluster with tProtProperty entries as an Input for
the function
setprotproperty in a call library function with:
Parameter Type : Adapt to type
Data Format: Pointer to Handle
but I always get an "exception within external code....."
What am I doing wrong?
How does a cluster & a "call library function node" look like that works?
Any help is really appreciated!
thanks
tom
,-Thomas Kerberger Physikalisch-Technische Bundesanstalt-.
| Abbestr.2-12 D-10587 Berlin fon: +49-30-3481338 |
| mailto:[email protected] fax: +49-30-3481386 |
`--------Labor 7.33 Messung thermischer Energie---------'

Thomas,
LabVIEW cannot call a DLL that has structures directly, you will need to create either a wrapper DLL or CIN that will take in all of the data individually construct the structure, and send it to the DLL function.
For more information on what a cluster looks like in native code, I would suggest creating a simple cluster, creating a Call Library Function Node on the block diagram with a cluster input. Then right-click on the Call Library Function Node and choose "Create .c file". This will generate the data structure for the cluster and give you a better feel for it. I would then suggest going to the Using External Code in LabVIEW manual that can be found in the LabVIEW Bookshelf (Start»Programs»National Instruments»LabVIEW 6»LabVIEW Manuals or »LabV
IEW 6.1»Search the LaBVIEW Bookshelf).
There is also the following: Developer Zone: Passing a Variety of Data Types from DLL to LabVIEW.
Randy Hoskin
Applications Engineer
National Instruments
http://www.ni.com/ask

Strange "Call Library function" behaviour

I'm facing a very strange problem during last week. I need to call some functions using Call library function node.
I have done many times in the past and I'm quite sure to call the function in the right way but I need help.
Synthetically I have to call in order the following functions:
DVRInitLibrary
DVRGetLibraryVersion
DVROpenConnection2
DVRConnectSite
DVRDisconnectSite
DVRCloseConnection
The first three functions works fine (I have the same result using it under Visual Studio!!). The function that I'm not able to call correctly is the following:
DVRRESULT WINAPI DVRConnectSite(
DVRHANDLE Handle,
LPCSTR SiteIP,
INT SitePort,
LPCSTR UserID,
LPCSTR Password,
INT AReadTimeOut
The function return a generic error code that doesn't give any useful information. Attached there is an image showing the way I'm calling the function. I did a lot of trials but I'm not able to understand the problem (under Visual Studio on the same machine It works!!). Same result on LabVIEW 7.1.1 or 8.6.1 or 2009 under Windows XP.
Regards
Golzio
Message Edited by Golziante on 05-17-2010 03:42 AM
Attachments:
CLN.jpg ‏71 KB

First of all thank you for your answers.
Taking into account your advice yesterday I was able to correctly connect to my DVR using the .NET solution (attached youcan find the block diagram).
As for the DLL call, you don't show your LabVIEW code, but be aware that a CStr is not the same as an LPCSTR. The latter is a pointer to a constant string. Thus, the DLL is expecting a pointer to a memory location that contains a string that will not change.
I got your point, but now I don't know how to pass an LPCSTR to this function. I also try to search here but I wasn't able to find some help.
Regards
Bye
Attachments:
BD_DOTNET.jpg ‏63 KB

[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

Where is pointer pointing to in Call Library Function

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