Custom C Code question: How do set extern variables from simulink model

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Alexander Dingwall 2019-5-13

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https://ww2.mathworks.cn/matlabcentral/answers/461815-custom-c-code-question-how-do-set-extern-variables-from-simulink-model

评论： Alexander Dingwall 2019-5-13

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I have a simple C code file that has four extern variables (three inputs, one output)

main.c:

#include <math.h>
#include "main.h"
extern float A1;
extern float A2;
extern float A3;
extern float OUTPUT;
void do_something(void) {
	OUTPUT = cos(A1) * sin(A2) * cos(A3);
}

main.h:

void do_something(void);

I wish to add this C code to my stateflow model and output the variable OUTPUT

This is how I currently have my custom c code setting

The 'include directories' sections only has a '.' so that every file in included (currently only main.h). And the 'source file' section is empty

My models are setup like this

I can the following error:

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James Tursa 2019-5-13

编辑：James Tursa 2019-5-13

"I don't want to define these variables using another .c file"

But that is specifically what the extern keyword does ... it instructs the compiler that these variables are defined in another file. All variables in your code have to be defined somewhere. You might have Stateflow specific code for setting these variables to values, but the variables still must be defined somewhere.

Alexander Dingwall 2019-5-13