How to create dll in Matlab to be used in Labview

Hi all,

I have problem with converting m-file in Matlab to dll file to be used in Labview. I used MCC to create dll from which Labview cannot find inputs and outputs. And is there any way to convert m-file to be used in Labview except using Matlab node due to its slow calculation speed? Thank you in advance.

Answer 1

[Kaustubha Govind]

I'm not sure exactly what kind of interface LabVIEW requires, but this is how you need to interface with a DLL generated using MATLAB Compiler. Note that you will also need to install the MATLAB Compiler Runtime (MCR) on the machine that the DLL is being deployed upon.

I wonder of what you actually need is a standalone DLL (independent of the MCR) - in that case using MATLAB Coder might be the better option.

[Fred Smith]

Kaustubha probably meant "MATLAB Coder might be the better option."

[Kaustubha Govind]

Oops! Yes, indeed. Thanks Fred. I fixed my answer.

[Jong-Hwan Kim]

Thank you for your answer. I used MCR and MCC to create dll, finally DLL was successfully created, but Labview still cannot find inputs and outputs. :(

[Kaustubha Govind]

Jong: How does LabVIEW "search" for interface exactly? Does it use the DLL header? Perhaps you might be able to ask NI's Technical Support team?

Answer 2

[David Roohy]

I've put together an example on how to do this from start to finish:

https://forums.ni.com/t5/Example-Program-Drafts/Walkthrough-for-Creating-a-MATLAB-DLL-That-Can-Be-Called-in/ta-p/3882891

Answer 3

[Michael Kaiser]

I'm up against the same issue. I've created both C shared libraries and C++ shared libraries, but cannot use in LabVIEW. How is the MATLAB runtime invoked, initialized?

Answer 4

[shubham kumar gupta]

GET A DLL FROM MATLAB:

mcc -v -B csharedlib:sumarray sumarray.m

create a scriptWrapper.c,scriptWrapper.h,scriptWrapper.def file[attached]

Now run below

mbuild -v sumarrayWrapper.c sumarray.lib LINKFLAGS="$LINKFLAGS /DLL /DEF:sumarrayWrapper.def" LDEXT=".dll" CMDLINE250="mt -outputresource:$EXE';'2 -manifest $MANIFEST"

now load this new scriptwrapper.dll in labview via import option, and add your old script.dll to this lvlib in labview

Always run loadFunction.vi before using your mainfunction.vi

Answer 5

[Ricardo Gutierrez]

Dear Shubham Kumar Gupta:

I tested the code for preparing matlab DLL for labview, I have some questions, maybe you can help me. How can I create the Wrapper.c file when you have multiple inputs and multiple outputs?

[Michele]

The same way you can do for a 1 o 1 script.

This's my script:

function [SNR, PhaseNoise] = Measure_SNR_w_SBX(FullName, FigurePath)
    close all
    [...]
end

When you compile this script you'll obtain two functions with a signature like this:

extern LIB_MINE_API 
bool MW_CALL_CONV mlxMeasure_SNR_w_SBX(int nlhs, mxArray *plhs[], int nrhs, mxArray 
*prhs[]);

extern LIB_MINE_API bool MW_CALL_CONV mlfMeasure_SNR_w_SBX(int nargout, mxArray** SNR_dB, mxArray** PhaseNoise_mean, mxArray* FullName, mxArray* Figure_path);

You can use both to write your wrapper based on your experience with MatLab C API.. I'm not very familiar with it so I used mlf* variant.

To call/wrap this you need to do something like that:

int wmlfMeasure_SNR_w_SBX(char* FullName, char* FigurePath, double* SNR_dB, double* PhaseNoise_mean)
{
    int result = 1;
    mxArray* mFullName = mxCreateString(FullName);
    mxArray* mFigure_path = mxCreateString(FigurePath);
    
    int nargout = 2;
    mxArray* mSNR_dB = NULL;
    mxArray* mPhaseNoise_mean = NULL;
    
    result = mlfMeasure_SNR_w_SBX(
        nargout, 
        &mSNR_dB, 
        &mPhaseNoise_mean, 
        mFullName, 
        mFigure_path);
    
    memcpy(SNR_dB, mxGetPr(mSNR_dB), sizeof(double));
    memcpy(PhaseNoise_mean, mxGetPr(mPhaseNoise_mean), sizeof(double));
    
    mxDestroyArray(mFullName);
    mxDestroyArray(mFigure_path);
    mxDestroyArray(mSNR_dB);
    mxDestroyArray(mPhaseNoise_mean);
    
    return result;
}

The only tricky part is to remember to use & when dealing with outputs parameters.