Why do I get this error Code generation does not support display for MATLAB classes. 'dsp.HDLIFFT' is a class. ?

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I am trying to call a function, which create dsp.IFFT system object, inside another for HDL Code generation.
My Code: %main function
function [out1,out2] = main(x,y,z)
%call subfunction 1
out1 = sub1(x);
%call subfunction 2
out2 = sub2(y,z);
end
subfucntion 2 codecode:
function [yOut,validOut] = HDLIFFT128(yIn,validIn)
persistent ifft128;
if isempty(ifft128)
ifft128 = dsp.HDLIFFT('FFTLength',128);
end
[yOut,validOut] = step(ifft128,yIn,validIn);
end

Accepted Answer

Walter Roberson
Walter Roberson on 13 Jul 2016
The connection between your two routines is not clear.
I suspect the problem might be because you have not put semi-colon on the end of your assignments to out1, so you are requesting that the result be displayed. If the result is not numeric then the coder will not know how to display it.
Note that you do not assign to out2 in your main function.
  2 Comments
Pablo Medina
Pablo Medina on 13 Jul 2016
Thanks!
The semi-colon works. But now I get this error:
The function 'HDLIFFT128' contains persistent variables 'ifft128' and has specialization 'HDLIFFT128_s1' associated with it. Function specializations containing persistent variables are not supported for fixed-point conversion. Consider rewriting your algorithm such that it does not use persistent variables within functions that require specialization.
Walter Roberson
Walter Roberson on 13 Jul 2016
I would suggest breaking it up into two pieces, one of which constructs the ifft128 object, and the other of which expects that object to be always input.

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