MATLAB S-function m-file template

gistfile1.matlab

% low-pass FIR filter code goes like this:
%trialfirS An M-file S-function 
function [sys,x0,str,ts] = trialfirS(t,x,u,flag)
 
h=fir1(32,0.5);

ipv=randn(1,100);

switch flag,

 %%%%%%%%%%%%%%%%%%
 % Initialization %
 %%%%%%%%%%%%%%%%%%
 case 0,
   [sys,x0,str,ts]=mdlInitializeSizes();

 %%%%%%%%%%%%%%%
 % Derivatives %
 %%%%%%%%%%%%%%%
 case 1,
   sys=mdlDerivatives(t,x,u);

 %%%%%%%%%%%
 % Outputs %
 %%%%%%%%%%%
 case 3,
   [sys,a,b]=mdlOutputs(t,x,u,h,ipv);
   disp(a)
   disp(b)
 %%%%%%%%%%%%%%%%%%%
 % Unhandled flags %
 %%%%%%%%%%%%%%%%%%%
 case {1,2,4,9},
   sys = [];

   
 %%%%%%%%%%%%%%%%%%%%
 % Unexpected flags %
 %%%%%%%%%%%%%%%%%%%%
 otherwise
   error(['Unhandled flag = ',num2str(flag)]);

end
% end trialfirS function

%
%=============================================================================
% mdlInitializeSizes
% Return the sizes, initial conditions, and sample times for the S-function.
%=============================================================================
%
function [sys,x0,str,ts]=mdlInitializeSizes()
sizes = simsizes;  % creating a structure variable
sizes.NumContStates  = 2;
sizes.NumDiscStates  = 0; 
sizes.NumOutputs     = 1;
sizes.NumInputs      = 1;
sizes.DirFeedthrough = 1;
sizes.NumSampleTimes = 1;
%
sys = simsizes(sizes);
x0= zeros(1,1);
str = [];
ts  = [0 0];
% end mdlInitializeSizes

%=============================================================================
% mdlOutputs
% Return the block outputs.
%=============================================================================
%
function [sys,a,b]=mdlOutputs(t,x,u,h,ipv)
sys=conv(ipv,h);
a=length(sys);
b=length(a);
return;
% end mdlOutputs