Using Embedded Matlab Function

Question

Sheetansh Kaushik 2013-5-31

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/77564-using-embedded-matlab-function

Good Day!

Please consider the following:

I want to generate a Square wave using the Matlab function: sqaure(),in Simulnk using "Emebedded Matlab Function". I tried the same by using the 'eml.extrinsic'; But i keep getting an error which states :- Function output 'y' cannot be of MATLAB type. Please see following code:

   function y  = fcn(~)
   %#eml
   eml.extrinsic('square');
   a=1;
   dc = 50;
   for i=1:100
   f=(6908:1:9856)';
   f=f*2*pi;
   t=0:0.5:22;
   y=a*square(f*t,dc); %ERROR
   end;

THe Embedded Function Block has no input; only 1 output and a Clock trigger. I am not able to upload images. SOrry for that.

The idea behind this block is to generate a square wave based on the defined frequency range. •a = amplitude •f = frequency •dc = duty cycle

Please let me know what I'm doing wrong? Or point me to what I have to read in order to understand my error? Or provide alternative methods to accomplish what I want.

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Answer 1

Sheetansh Kaushik 2013-6-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/77564-using-embedded-matlab-function#answer_87491

Consider the following code:

function y = fcn %#eml

eml.extrinsic('square', 'linspace');

a = 1; dc = 50; f = 2*pi* (6908:1:9856);

t = f; % pre-allocation of f

t = linspace(0, 1000000, numel(f)); % re-assignment

y = t; % pre-allocation of t

y = a*square(t.*f, dc); % element wise multiplication and Then final assignment

If you will notice here, the pre-allocation solves the problem of difference in datatype. The compiler cannot determine the type and size of the outputs of extrinsic functions. Therefore, the compiler will be forced to keep it "MATLAB type" (AKA an mxArray). The only thing you can do with an mxArray in Embedded Matlab, is pass it onto another extrinsic function, but you cannot assign it to anything directly.

You'll have to tell MATLAB the type and size of the extrinsic function's output before calling the extrinsic function. You can do this by pre-alocating the variable with the same type and size of the (expected) output.

---This answer was given to me!!--- i didnt come up with it!! Hope it helps people!