matlabmatlab-coder

Matlab coder: "All inputs must be constant"

I'm using Matlab Coder to convert this code to C++:

fs = 50;
[b,a] = butter(3,0.5/(fs/2),'high');
...
% Other code using fs

Then, I get this error: "All inputs must be constant".

If I do: [b,a] = butter(3,0.5/(50/2),'high');, it works.

I found this post: Constants and Matlab Coder

So I tried:

fs = 50;
[b,a] = coder.const(@butter,3,0.5/(fs/2),'high');

But it still reports the same error. How can I fix this?

Solution

  • Define Class Properties with Constant Values

    In ConstInput.m

    classdef ConstInput
   properties (Constant)
      fs = 50;
   end
end

    Then rename fs as ConstInput.fs. (Unfortunately, Shift+Enter does not work. Maybe this links helps about changing variable names.)