Multiple definition of a variable in a multi-file sketch

Projects Programming
15

Thanks gfvalvo,

I got it to work by declaring and defining the global variables in the same cpp file, and using the extern keyword in the other files that reference a global variable.

Apparently my original problem occurred because I declared and defined the global variables in the header file, which was included in multiple cpp files. That is why I got the multiple definition errors.

Here is the final code (I added a define_global_var.cpp file to the original four files):

/* FILE: multi_file.ino */

#include "multi_file.h"

void setup() {
}

void loop() {
  fnc_1();
  fnc_2();
}

/* FILE: multi_file.h */

#ifndef multi_file_h
#define multi_file_h

#include "Arduino.h"

extern byte var_1;
extern byte var_2;

void fnc_1( void );
void fnc_2( void );

#endif

/* FILE: define_global_var.cpp 
 *
 * Declares AND define global variables, which is normally done in the ino file. 
 */

#include "Arduino.h"

byte var_1 = 0;
byte var_2 = 0;

/* FILE: fnc_1.cpp */

#include "multi_file.h"

void fnc_1( void ) {
  var_1 = 1;
}

/* FILE: fnc_2.cpp */

#include "multi_file.h"

void fnc_2( void ) {
  var_2 = 1;
}