coder.excentric not working when compiling with TwinCat Target

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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');

Accepted Answer

Tom Bryan
Tom Bryan on 17 Mar 2014
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?
  2 Comments
Dries billiet
Dries billiet on 20 Mar 2014
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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More Answers (1)

Kaustubha Govind
Kaustubha Govind on 13 Mar 2014
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.
  1 Comment
Ketan
Ketan on 15 Mar 2014
Here are few other options:
- Implement the desired filter coefficient calculation yourself in MATLAB and call this code in your function block
- Try to leverage some of the more advanced filter functionality in DSP system toolbox:

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