Function node on array
I want to take an array (e.g. [1,3,5,7,8]) and apply a function to each member, and then return an array afterwords
(e.g. [exp(1) -2, exp(3) -2, exp(5) -2, exp(7) -2, exp(8) -2)] )
Could someone please tell me how to do this. I would very much appreciate it!
Thank you,
inlkjlkj
Here is some sample code. If you wire an array in, an array comes out. Mind that you don't use a for loop, as that will auto index and not maintain the array.
I hope the image clears it up. I am not sure what you are seeing. Perhaps you could upload some code or a picture?
Attachments:
array math.GIF 3 KB
Similar Messages
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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: \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: \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 -
Calling a library function node much faster than labview code?
Hi, I wrote a labview routine to perform a multiple tau autocorrelation on a large array of integers. A multi tau autocorrelation is a way to reduce the computation time of the correlation but at the expense of resolution. You can taylor the multitau correlation to give you good resolution where you need it. For instance, I require good resolution near the middle (the peak) of the correlation, so I do a linear autocorrelation for the first 64 channels from the peak, then I skip every second channel for the next 32, then skip every 4th channel for 32 more, then skip every 8th for 32 channels... etc.
Originally, I wrote my own multitau calculation, but it took several hours to perform for just 1024 channels of the correlation of around 2million points of data. I need to actually do the the correlation on probably 2 billion or more points of data, which would take days. So then I tried using labview's AutoCorrelation.vi which calls a library function. It could do a linear autocorrelation with 4 million points in less than a minute. I figured that writing my code in C and calling it using a call library function node would be faster, but that much faster?
Finally, I wrote some code that extracts the correlation data points that I would've got from my multitau code from the linear correlation function that I get from the AutoCorrelation.vi. Clearly this is not optimal, since I spend time calculating all those channels of the correlation function just to throw them away in the end, but I need to do this because the final step of my procedure is to fit the correlation function to a theoretical one. With say 2million points, the fit would take too long. The interesting thing here is that simply extracting the 1024 point from the linear autocorrelation function takes a significant amount of time. Is labview really that slow?
So, my questions are... if I rewrite my multitau autocorrelation function in C and call it using a call library function node, will it run that much faster? Can I achieve the same efficiency if I use a formula node structure? Why does it take so long just to extract 1024 points from an array?
I've tried hiding indicators and this speeds things up a little bit, but not very much.
I'll attach my code if you're interested in taking a look. There is a switch on the front panel called 'MultiTau'... if in the off position, the code performs the linear autocorrelation with the AutoCorrelation.vi, if in the on position, it performs a multitau autocorrelation using the code I wrote. Thanks for any help.
Attachments:
MultiTauAutocorrelate.vi 627 KBHi,
The C routine that AutoCorrelation.vi is using is probably a higly optimised routine. If you write a routine in LabVIEW, it should be less then 15% slower. But you'd have to know all ins and outs of LabVIEW. How data is handled, when memory is allocated, etc. Also note that the AutoCorrelation.vi has years of engineering behind it, and probably multiple programmers.
It might even be possible that the c code uses an algorithmic improvement, like the Fast Fourier Transform improves speed on the Fourier Transform. I think the autocorrelation can be done using FFT, but that isn't my thing, so I'm not sure.
For a fair comparation, posting the code in this forum was a good idea. I'm sure together we can get it to 115% or less of the C variant. (15/115 is just a guess, btw)
I'm still using LV7.1 for client compatibility, so I'll look at the code later.
Regards,
Wiebe.
"dakeddie" <[email protected]> wrote in message news:[email protected]...
Hi, I wrote a labview routine to perform a multiple tau autocorrelation on a large array of integers. A multi tau autocorrelation is a way to reduce the computation time of the correlation but at the expense of resolution. You can taylor the multitau correlation to give you good resolution where you need it. For instance, I require good resolution near the middle (the peak) of the correlation, so I do a linear autocorrelation for the first 64 channels from the peak, then I skip every second channel for the next 32, then skip every 4th channel for 32 more, then skip every 8th for 32 channels... etc. Originally, I wrote my own multitau calculation, but it took several hours to perform for just 1024 channels of the correlation of around 2million points of data. I need to actually do the the correlation on probably 2 billion or more points of data, which would take days. So then I tried using labview's AutoCorrelation.vi which calls a library function. It could do a linear autocorrelation with 4 million points in less than a minute. I figured that writing my code in C and calling it using a call library function node would be faster, but that much faster?Finally, I wrote some code that extracts the correlation data points that I would've got from my multitau code from the linear correlation function that I get from the AutoCorrelation.vi. Clearly this is not optimal, since I spend time calculating all those channels of the correlation function just to throw them away in the end, but I need to do this because the final step of my procedure is to fit the correlation function to a theoretical one. With say 2million points, the fit would take too long. The interesting thing here is that simply extracting the 1024 point from the linear autocorrelation function takes a significant amount of time. Is labview really that slow?So, my questions are... if I rewrite my multitau autocorrelation function in C and call it using a call library function node, will it run that much faster? Can I achieve the same efficiency if I use a formula node structure? Why does it take so long just to extract 1024 points from an array?I've tried hiding indicators and this speeds things up a little bit, but not very much.I'll attach my code if you're interested in taking a look. There is a switch on the front panel called 'MultiTau'... if in the off position, the code performs the linear autocorrelation with the AutoCorrelation.vi, if in the on position, it performs a multitau autocorrelation using the code I wrote. Thanks for any help.
MultiTauAutocorrelate.vi:
http://forums.ni.com/attachments/ni/170/185730/1/MultiTauAutocorrelate.vi -
Issue using DLL / library function node
Hi All
I am using labview 8.2 / 8.0
I am writing a wrapper DLL to convert compex data types of a DLL to simpler ones for labview intefacing.
I have read the forums on all related items and could not find a solution.
I have cut my code back to basics and I am still getting error 1097 with 8.2 and a crash with 8.0
The error occurs as follows:
1) Start labview, open the vi.
2) Run vi - everything works (so far the wrapper DLL I am writing call just does a simple open handle and close handle on a driver dll).
The handle is passed back to the vi, and everything is good.
I can re-run the application numerous times and it always works
3) IF I close the vi, but not labview and re-open I get the following:
Labview 8.0 crashes on closing the vi
Labview 8.2 does not crash, but I get error 1097 if I re-open and run the vi.
So it seems like it's almost working but the issue comes on the release of the dll from one invocation of the vi to another.
I don't know what the error is, but I've tried everything I can think of! Any suggestions would be appreciated!
Note: I am not passing any arrays at the moment, but I am passing one unsigned 32 bit int pointer. I declare a constant for this in the call, so there is something for the pointer to use, and it seems to return the data ok.Hi Kaem,
Thanks for your reply.
I have written C++ standalone programs that link to the DLL and these work fine. I have even called my wrapper DLL from a C++ program and that too works fine (just to check if the wrapper would cause issues there). I have a hunch that it is actually the DLL that my wrapper is 'wrapping' that is causing the issue, but I guess I don't know for sure.
The difference (IMHO) is that these C++ programs all run through once and then exit, so everything works fine. However if they load the DLL and unload it and try to load it again, maybe there would be an issue. I think labview is doing this.
The reason I think labview does something funny with the DLL after you exit a VI (but not labview) is because labview crashes in 8.0 when the VI is closed (8.2 is ok, but the next DLL invocation fails when the VI is reopened), so something must be happening at this point - and I think it's an ungraceful unload of the DLL.
Also, I've noticed that I cannot overwrite my wrapper DLL with a new version until I exit a VI - so labview is definitely doing something on VI close - it's releasing some lock on the DLL.
I don't use any consts in my code - sorry if I indicated that. What I have is a U32 constant in labview, and I connect that to the input of the library function node, and pass it as a pointer. And the DLL writes into this then. Are you saying that a labview constant cannot be used as an input to a function and passed as a pointer ? What should I use instead, a control?
Note: while writing - I just tried that - same error - so I don't think this is it.
I'm willing to take any and all suggestions!!
Cheers
John -
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 -
Mysql without odbc call library function node
hy!
i'm trying to send a SELECT query to a mysqlserver by calling the needed functions in libmysql.dll
i get a successful connection and can read the server-version, but the result of the query which should be something like DATETIME|INT|INT and so on is quite a mess:
“À›ÀŸÀ2012-02-13 08:40:46
I read in the documentation of fetch_lenght, that this function should recieve an array, but how can i tell a Call llibrary function node to return a array?
MySQL_fetch_lengths
libmysql.dll i used: mysql-connector-c-noinstall-6.0.2-win32.zip
Attachments:
mysqlquery.vi 13 KBHow to read a function return pointer that is an array, can be seen here. Kind of messy I know, but interfacing C is a mess in comparison to LabVIEW programming.
For the rest I think I fully agree with Dennis. Lots of sweat and work for a questionable benefit. And your strange data probably comes from binary and text data being mixed in the returned pointer based on the column datatype. Good luck with creating a LabVIEW VI library that can handle that transparently.
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions -
[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 -
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 advanceDid 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
DAveHi 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 -
Message mapping: one as many, function node
hi
how to use - one as many - function node in mapping. i want to mapping one value from source structure to many fields in target structure. but i dont know the exact functionality of - one as many -
kindly solve my issue
regards
manoHi,
Check out this example from SAP, which demos the use of the function oneAsMany:
[http://help.sap.com/saphelp_nw04/helpdata/en/38/85b142fa26c811e10000000a1550b0/frameset.htm]
Hope this helps,
Sumant. -
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 -
Use of Call Function Node vi, with char type pointer
I want to be able to use a certain function from C++ DLL, and I followed the TOOLS>>IMPORT>>SHARED LIBRARY(.dll) wizard. Where I located my header file and the dll file.
However i am getting an error (1097). This is the function with the paramaters:
void Function_Name(unsigned char *L, unsigned char *H, unsigned in Len, unsigned char Adr);
I don't think, that I configured my Call Function Node, correctly. How should i set the paramaters settings of the first 2? I have tried Numeric, unsigned (and signed) Int (32, 16), pass pointer value. to accomodate the first two varaibles.
Please someone help, what should I do to accomodate the unsigned char pointers, so that I can used the function in labVIEW?Hi Safe,
The error you're encountering has the following description (I'm sure you've already looked this up-posting here for clarity for other readers):
LabVIEW: An exception occurred within the external code called by a Call Library Function Node. This might have corrupted LabVIEW's memory. Save any work to a new location and restart LabVIEW.
Typically, this happens for one of just a few reasons:
Memory was overwritten (e.g. you passed a buffer of N bytes, but N+X bytes were modified, and an exception was thrown.
A bad pointer was passed. (This is probably not the case.)
Arguments were not passed to the function properly. (Calling conventions)
Function wasn't called from the proper thread.
Some other reason (only can be determined by inspecting in a debugger).
I've attached some pictures of how I'd configure the dialog, but there are two critical things you have to know: calling conventions and thread safety. Those are things defined by the DLL. In Windows, C vs. 'Standard' (a.k.a. Pascal) calling conventions MUST be correct, as they affect how arguments are passed on the stack. If this is wrong, then, for example, where arg1 is expected to be an unsigned char *, you may actually only pass an unsigned char. Dereferencing that number as a pointer will at best crash, at worst appear to be a valid address and silently corrupt memory.
I suggest double-checking the calling conventions. 'stdcall' is still quite common, but not the default setting in the Call Library Function dialog.
Best regards,
intvstefve
intvsteve
LabVIEW R&D
Attachments:
dllconfig11.JPG 40 KB
dllconfig21.JPG 41 KB -
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
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