C code not working inside MATLAB System

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Carlo Savorgnan
Carlo Savorgnan 2016-4-12
评论： Ryan Livingston 2016-4-12
I'm trying to interface some C code inside a MATLAB system derived class. The C function I want to use multiplies by 3 the input argument. File "triple.h":
#ifndef __TRIPLE_H__
#define __TRIPLE_H__
#ifdef MATLAB_MEX_FILE
#include <tmwtypes.h>
#else
#include "rtwtypes.h"
#endif
double triple(double in);
#endif
File "triple.c":
#include "triple.h"
double triple(double in)
{
return in*3;
}
I defined a MATLAB function "call_triple" so that I can call the C function. File "call_triple.m":
function out = call_triple(in)
%#codegen
assert(isa(in, 'double'));
if coder.target('MATLAB')
out = call_triple_mex(in);
else
out = double(0.0);
out = coder.ceval('triple', in);
end
I compiled with the MATLAB coder "call_triple" to obtain "call_triple_mex":
>> codegen -config:mex call_triple triple.h triple.c
Now I can use call_triple from MATLAB command line:
>> call_triple(2.4)
ans =
7.2000
Finally I implemented the class "triple_system"
classdef triple_system < matlab.System & coder.ExternalDependency
...
... more code
...
function out = stepImpl(~, in)
out = call_triple(in);
end
...
... more code
...
The class works from the command line:
>> obj = triple_system;
>> step(obj, 3.2)
ans =
9.6000
The problem arises when I use the class inside a "Matlab system" block inside Simulink and I select the option "Simulate using: code generation". The output of the Simulink block returns a number which makes no sense to me (like 1689233153 or similar big numbers). The block works fine when I select: "Simulate using: interpreted execution".
What am I doing wrong? I wold expect the same behaviour from the two simulation methods.
Thanks
Carlo

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采纳的回答

Ryan Livingston
Ryan Livingston 2016-4-12
You likely need to add coder.cinclude('triple.h') in the System Object to include the header for triple. Without the declaration of triple, the C compiler assumes that the signature is int triple(int) which results in the unexpected behavior that you are seeing.
  2 个评论
Carlo Savorgnan
Carlo Savorgnan 2016-4-12
I added coder.cinclude('triple.h') inside the definition of call_triple and now it works.
Thank you!
Ryan Livingston
Ryan Livingston 2016-4-12
Glad to hear it, that's a hard error to track down.

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