Sonsivri

Hi all. I'm having a problem with compiling my program because i want to use the same array inboth my main c file and my other c file.

Example: main.c

#include <absacc.h>
#include <stdio.h>
#include <SPI.h>
#include <DS1305.h>
#include <SDcard.h>

unsigned char rdat[12]; //To be used in main.c and SDcard.c

However if i declare it in both i get an error: Multiple public definitions
and if i declare it in only 1 of the two the compiler thinks that the array is undefined in one of them.

Please help me out. Can i solve this problem by defining the array in the SDcard.h file instead or any other solutions??/

You have to use extern , like this:

main.c
-------

#include <absacc.h>
#include <stdio.h>
#include <SPI.h>
#include <DS1305.h>
#include <SDcard.h>

unsigned char rdat[12];
.
.
----------------------

SDcard.c
-----------
.
.
extern unsigned char rdat[12]
.
.
.
---------------------------

In SDcard.c this means that rdat[12] is externaly defined (in this case in main.c) and can be used across files.

Hope that this works.

Regards

Thanks it worked. Didn't know it was that simple.

There's the way to declare all the related vars just once:

"MySDLib.h"
-------------------------
// here follows block of SD-related variables declarations:
#ifndef  _SD_Card_Lib_
  #define  _SD_DefArea_ extern
#endif
_SD_DefArea_   int   iVar1;      // all SD-related variables are declared just once, all in one place - this will ease the control over the code and variables
_SD_DefArea_   char   cVar2;      // ...
_SD_DefArea_   unsigned char rdat[12];   //
...
#undef  _SD_DefArea_
...



"SDLib.c"
-------------------------
#define  _SD_Card_Lib_   // this will turn extern OFF
#include <MySDLib.h>   // all SD-vars will be declared as usual

// SDLib functions follows...
...



"main.c"
-------------------------
// #define  _SD_Card_Lib_   // omitting this #define will turn extern ON

#include <MySDLib.h>   // all SD-vars will be declared as external
...

Hi

yor can share global variable(s) in other files by using "extern"

for example

//-------[file A.C]--------
char arr[10];           

.....
.....
.....

//-------[file B.C]--------
// if you want to access arr in file A.C, you can  declar in the top of file B.C

extern char arr[10];

.....
.....
.....