Programming Matlab function into simulink

I'm trying to program an arduino due to record and do some calculations with the signal. To do that, i downloaded the arduino support package. Into simulink, i'm able to read the ecg signal, with an analoge input, but it needs to be filtered so i used the matlab function block and programmed the function below: (ecg is buffer of 10000 samples, sampled at 500Hz)

         function y_filter  = stats(ecg,fs,buffersize,bufferstep)
         %#codegen

         fcuts = [8 20];
         mags = [1 0];
         devs = [0.05 0.01];

         [n,Wn,beta,ftype] = kaiserord(fcuts,mags,devs,fs);
         h = fir1(n,Wn,ftype,kaiser(n+1,beta),'noscale');  

         y_filter=filtfilt(h,1,ecg);

I'm getting the following errors

All inputs must be constant.

Function 'MATLAB Function' (#23.282.331), line 15, column 5: "[n,Wn,beta,ftype] = kaiserord(fcuts,mags,devs,fs)" Launch diagnostic report. Component: MATLAB Function | Category: Coder error

 Undefined function or variable 'n'. The first assignment to a local variable determines its class.

Function 'MATLAB Function' (#23.283.284), line 15, column 6: "n" Launch diagnostic report. Component: MATLAB Function | Category: Coder error

 Undefined function or variable 'Wn'. The first assignment to a local variable determines its class.

Function 'MATLAB Function' (#23.285.287), line 15, column 8: "Wn" Launch diagnostic report. Component: MATLAB Function | Category: Coder error

 Undefined function or variable 'beta'. The first assignment to a local variable determines its class.

Function 'MATLAB Function' (#23.288.292), line 15, column 11: "beta" Launch diagnostic report. Component: MATLAB Function | Category: Coder error

 Undefined function or variable 'ftype'. The first assignment to a local variable determines its class.

Function 'MATLAB Function' (#23.293.298), line 15, column 16: "ftype" Launch diagnostic report. Component: MATLAB Function | Category: Coder error

 Undefined function or variable 'n'. The first assignment to a local variable determines its class.

Function 'MATLAB Function' (#23.346.347), line 16, column 14: "n" Launch diagnostic report. Component: MATLAB Function | Category: Coder error

 Undefined function or variable 'h'. The first assignment to a local variable determines its class.

Function 'MATLAB Function' (#23.411.412), line 18, column 23: "h" Launch diagnostic report. Component: MATLAB Function | Category: Coder error

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Any help how i could fix the problem or another (better) solution to filter my ecg? it should be used to monitor a heart signal online.

Answer 1

[Tushar Sinha]

Hi Thogoe,

The issue might be occurring because the function variables are not allowed to change size to be able to generate code. Initializing all the variables to some default value at the start of the function might help resolve the issue.

You can also refer to the link below which talks about a similar issue:

http://www.mathworks.com/matlabcentral/answers/40790-simulink-user-defined-function-undefined-variable-or-function

I hope this helps!

Thanks,

Tushar

Answer 2

[fikana cantri]

how do you solve the issue ? i have the same problem