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Hello all, background A while ago I wrote a dll wrapper to get data from dedicated test-hardware. For this hardware there is a dll available. To use this dll you need to use an callback function. If you need to use a dll in Labview which needs a callback you need to write the callback in C code and use a Labview C lib to get the data into Labview, basically my dll takes care of this problem . Enhance the code and way of working more efficient The code I wrote code works fine. However I did not use / test it for hours on a row. And sometimes If I make a mistake when changing the code I run into problems. I was able to fix all the errors and problems however it was not the most efficient way of working. For instance If there is a serious error in the code the dll I need for the hardware can crash, it can make my wrapper crash, which will in return make Labview crash. This makes the way of coding inefficiënt and it will not enable me to read my C++ book etc etc. Example pseudo code I did try to extract some main points of intrest from the code, I did add some comment in the code. I hope someone can give me some general guideline or advice what to read. At this time I am reading: Unhandled C++ exceptions I think I might be able to use it, I did not use this before so advice would be welcome. Thank you all for the help ! // .. // This is a part of the code only intended to have a talk about how to catch errors // It is not complete and intended as Pseudo code // .. int __stdcall MyDriverLoads(const int NumberToInitialise,const bool enableAnotherOption , const char *const path , LVUserEventRef *rwer) { // loads the dll // Q -- I can check if (F_functionname !=0), if it is not 0 then I can proceed if the function returns 0 I can return an error to Labview Extern_dll = Load_Extern_dll(); // Get the functions I need from the dll p2_ExternDriver F_ExternDriver = (p2_ExternDriver)GetProcAddress(Extern_dll, "_ExternDriver"); p2_Initialise F_Initialise = (p2_Initialise)GetProcAddress(Extern_dll, "_Initialise"); p2_AdapterCount F_AdapterCount = (p2_AdapterCount)GetProcAddress(Extern_dll, "_AdapterCount"); p2_StartLogging F_StartLogging = (p2_StartLogging)GetProcAddress(Extern_dll, "_StartLogging"); p2_StopLogging F_StopLogging = (p2_StopLogging)GetProcAddress(Extern_dll, "_StopLogging"); // When there are adapters found I tell it in Labview adapterCount = F_AdapterCount(); // Get the callback function adress, if adress == 0 I can see something is wrong void(__stdcall *p2_CallbackFunction_t) (pt2Obj , const LogData & ) = &CallbackFunction; // Q -- I could use try {} and catch {} however I do not have acces to the source code of the dll so, // I do not know if they used // trow "The Blue error" , or // trow "The Red error" ret = F_ExternDriver(adapterCount, enableLogFile, path, *p2_CallbackFunction_t, pt2Obj); // This tels the dll to start logging before this command you will not receive data in Labview ret F_StartLogging(1,2,3); // Labview is receiving data thats great !!! return ret; // Q -- Labview has been receiving data for a hour what happens if the used extern dll crashes ?? // If the dll crashes when return is passed I can not use try() and catch anymore. // } extern void __stdcall CallbackFunction(pt2Obj , const LogData & ) { // There is a lot to do here // do stuff!! // I did not write everything here err = PostLVUserEvent(*event_ref, &tmpEvent); }

Hello I hope someone can help me, I have been trying to get this to work for days but no success yet. What I want to do I got a dll with a wrapper, this dll and wrapper can be used for a special datalogger. The wrapper contains multiple functions, I have got some of them working using a CLFN, for instance I can read a jumper setting from the datalogger in LabView. So far everything is fine. Of course I am not that interested in the jumper setting, I would rather use the datalogger to log data. I need to run one function to start logging. When there is enough data in the databuffer of the driver dll it will call a callback function I need to write in Labview, here is the function which starts the logging as described in the header file: Int LOGEXPORT __sdcall LOG_StartLogging{const char ** logFilename, ptLogCallbackfunction ptFunction, ptObject ptObject} logFilename needs to be a NULL pointer, from my understanding I do not need to do anything with it. Only provide it. If I do not do anything with it some data is saved at a default location. ptLogCallbackfunction, as far as I know I need to provide a pointer to the callback function ptObject ptObject, this must be a void pointer The header also provided how the callback function could look like in 😄 Void __stdcall callbackLog(ptObject object, const int ArraySize, const StructLogdata *const logDataArray) { // copy data from logDataArray for use in my code } StructLogdata is a struct with different datatypes. What I did try I did a search on internet there are some examples about callback functions, most of them point to NET and active X. They use a reg Event Callback. I did read the helpfile at the end of the helpfile there is the text: “Use the Event structure or the Register For Events function to register and handle non-.NET or non-ActiveX events dynamically” I am having a hard time to find a proper example. I did find this site with some information: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P8XJSA0&l=nl-NL and this one about the refnum: https://forums.ni.com/t5/LabVIEW/Passing-Event-Refnum-to-Call-Library-Function/td-p/4107748 So I did make a user event, I wired a static Vi ref containing a callback vi to the input of this user event. I did wire the user event to a Reg event and wired the event registration refnum to the start logging dll call library function node function pointer input and also to an event structure. I did place a counter in the event structure. But nothing happens besides for an exception which makes Labview crash. The parameters I did use in the call library function are: logFilename: type numeric, datatype: Signed Pointer-sized int Pass: pointer to value ptLogCallbackfunction: type: adapt to type, Data format handles by value (tried all options) ptObject: same as logFilename I did try a lot of different things. Writing them in this post will result in chaos and I don’t want that. I hope someone can help me with a simple example how to make this work, or point me into the correct direction. Thank you all for the help!

Hello to you all, Sending a cluster with int's I did manage to send an array with clusters from a dll to Labview. Thank you all for the help. You can find the link here: https://lavag.org/topic/22877-can-someone-help-me-with-an-example-for-an-existing-wrapper-dll-which-uses-function-pointer-with-callback-function/#comment-147496 It works fine I am very pleased with it. 😃 Sending a text string I did got a example here: https://forums.ni.com/t5/Example-Code/Posting-Events-to-a-LabVIEW-Event-Structure-From-a-Dll/ta-p/3996283 Tested it and it works fine. Again I am happy 😃 Sending a cluster with int's AND a string Now I want to send a cluster / struct with a couple of int's AND a string of text. I Got a example of how to send text from a C / C++ wrapper to Labview, can someone please help me out? The thing I do not get is, how to combine the both examples. Is "sizeof(structSample)" valid with a LStrHandle in it? How do I copy the data from the string to the struct, etc. Can someone change the code example or help me with the example so it works? I did add some text to the example code to make it more clear I added +++ signs in my comment in the code. Hope someone can help me. Thanx ! // LVUserEvent.cpp : Defines the entry point for the DLL application. // #include "stdafx.h" #include <stdio.h> #include "LVUserEvent.h" #define STRING_LENGHT 256 //Can be any size // ++++ I want to send this Cluster/Struct to Labview typedef struct { int firstInt; int secondInt; int thirdInt // +++++ I try to add this, Gues this will not work .. see extcode.h LStrHandle textString[TEXT_STRING_SIZE]; }structSample; typedef struct{ int32_t size; structSample elm[1]; }totalstructSample, **structHdl LVUSEREVENT_API void SendEvent(LVUserEventRef *rwer) { LStrHandle newStringHandle; //Allocate memory for a LabVIEW string handle using LabVIEW's //memory manager functions. newStringHandle=(LStrHandle)DSNewHandle(sizeof(int32)+STRING_LENGHT*sizeof(uChar)); // +++++ OW no another one ... structHdl = (eventHdl)DSNewHandle(sizeof(totalstructSample)); Sleep(2000); PopulateStringHandle(newStringHandle,"+++ Dear int I don't want you in my PostLVUserEvent"); //Post event to Event structure. Refer to "Using External Code //with LabVIEW manual for information about this function. PostLVUserEvent(*rwer,(void *)&newStringHandle); return; } void PopulateStringHandle(LStrHandle lvStringHandle,char* stringData) { //Empties the buffer memset(LStrBuf(*lvStringHandle),'\0',STRING_LENGHT); //Fills the string buffer with stringData sprintf((char*)LStrBuf(*lvStringHandle),"%s",stringData); //Informs the LabVIEW string handle about the size of the size LStrLen(*lvStringHandle)=strlen(stringData); return; }

Hi everyone. I wrote wrapper in Visual Studio for OpenCV calibrateCamera() function. Every operation like converting 1D array of points to vector<vector<Point2f>> etc, works ok, except most important thing. When function ()calibrateCamera is called, LabVIEW crashes. When this line is commented out, dll works ok (at least labview is still alive). Im out of ideas. I suspect that this is problem with memory management but i dont have an idea where it cames from. Function do not operate directly on data passed from LabVIEW. Ultimately I can compile code as exe and call it via cmd, but I'm curious why such a thing appears. Thanks for your precious time! Zyga dll source (if you need i can enclose some sample input data): #include <opencv2/core/core.hpp> #include <opencv2/calib3d/calib3d.hpp> #include <extcode.h> using namespace cv; using namespace std; static void calcBoardCornerPositions(Size boardSize, float squareSize, vector<Point3f> &corners); static void arr2vect(float *APoints,int *Asize, vector<vector<Point2f>> &imagePoints); extern "C" { float __declspec(dllexport) Calibrate(float *APoints, int *Asize, int width, int height, float squareSize) { //initialize variables vector<vector<Point2f>> imagePoints; Size boardSize; boardSize.height = height; boardSize.width = width; Mat cameraMatrix = Mat::eye(3, 3, CV_64F), distCoeffs = Mat::zeros(1, 1, CV_64F); cameraMatrix.at<double>(0,0) = 1.0; vector<Mat> rvecs, tvecs; vector<vector<Point3f>> objectPoints(1); Size imageSize; imageSize.width = 2040; imageSize.height = 2040; arr2vect(APoints, Asize, imagePoints); // prepare imagePoints calcBoardCornerPositions(boardSize, squareSize, objectPoints[0]); //prepare objectPoints objectPoints.resize(imagePoints.size(),objectPoints[0]); //calibrate double rms = calibrateCamera(objectPoints, imagePoints, imageSize, cameraMatrix, distCoeffs, rvecs, tvecs); return rms; } } //definitions static void arr2vect(float *APoints,int *Asize, vector<vector<Point2f>> &imagePoints) { int page = *(Asize); int row = *(Asize+1); int col = *(Asize +2); Point2f pointBuf; vector<Point2f> vectBuf; for (int i = 0; i<page; i++) { for (int j = 0; j<row; j++) { pointBuf.x = *(APoints + (i*(row*col))+j*2); pointBuf.y = *(APoints + (i*(row*col))+j*2+1); vectBuf.push_back(pointBuf); } imagePoints.push_back(vectBuf); vectBuf.clear(); } vectBuf.clear(); } static void calcBoardCornerPositions(Size boardSize, float squareSize, vector<Point3f> &corners) { corners.clear(); for( int i = 0; i < boardSize.height; ++i ) for( int j = 0; j < boardSize.width; ++j ) corners.push_back(Point3f(float( j*squareSize ), float( i*squareSize ), 0)); }

Hi guys, I have a wrapper to a DLL which was written in C, now the DLL used from the wrapper was updated to a new version, so I have to reload the DLL into the "Call library function" for each function of the wrapper that I've already created and it is a very boring job. Therefore, I would like to know if exists a trick to use to update all functions of a dll wrapper in one shot? Does it exist?