coder.excentric not working when compiling with TwinCat Target

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Dries billiet 2014-3-11

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评论： Dries billiet 2014-3-20

Hello,

I am working on a case where I put simulink generated code into an embedded PC. My model works fine in simulink, but when I try to generate the code for my embedded controller, it fails. The fault message is the following.

_Failed to eliminate a call to the MATLAB function 'butter'. For non-simulation builds, calls to unsupported MATLAB functions are eliminated if they do not affect function out puts. Function 'filter1/MATLAB Function' (#34.92.133), line 6, column 1: "[a,b] = butter(w,[x y]/(z/2), 'bandpass')"

I found out that the actual problem is that coder.extrinsic('butter') is not allowed by external compilers. But I really need a way to create a butterworth filter in a matlab function block.Because my system needs a filter with adaptable bandwith. Is there somebody who knows a possible workaround?

     function [a,b] = fcn(w,x,y,z)
      a=zeros(1,(11));
      b=zeros(1,(11));
      coder.extrinsic('butter');
      [a,b] = butter(w,[x y]/(z/2), 'bandpass');

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Answer 1

Tom Bryan 2014-3-17

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If you leave out the coder.extrinsic('butter') command, then it will generate code for the embedded processor. But, in that case, the butter() command requires constant inputs.

It is possible to create a table of constant coefficient values that you can index into as a function of discrete w, x, y, z values. Would that be a workable option for you?

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Dries billiet 2014-3-17

Nice idea! I'll try to work this one out!

Dries billiet 2014-3-20

This does non't work. Because the coeficients are non constants. But it brougt me on the idea of adding a 'database' (read: big array) with the calculated transfert functions already in the array.

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Answer 2

Kaustubha Govind 2014-3-13

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You can either implement the functionality yourself in C, or find a third-party library that does so, and call it in your MATLAB code using coder.ceval.