Question

I’m starting programming a dspic33 from Microchip and i’m having problems when I try to return an extern variable. My code is divided in 3 files, and is something like this:

main.c  

#include <stdio.h>           /*printf definition ... */
#include "clock.h"
volatile unsigned long count = 0;

int16_t main(void)
{

clock_init();

 while(1)
{
  if(flag)
   {
    printf("MAIN:count = %lu clock_time %lu",count, clock_time());
    flag = 0;
   }
 }
 return 0;
}

---

clock.h  

...
extern volatile  unsigned long count;
...

---

clock.c

#include "clock.h"
void __attribute__((__interrupt__, no_auto_psv)) _T1Interrupt(void)
{
 count++;
 flag=1;   
 IFS0bits.T1IF = 0;   
}

unsigned long clock_time(void)   
{
return count;
}

The output is something like:

MAIN:count = 1 clock_time : 590106798  
MAIN:count = 2 clock_time : 590106798  
MAIN:count = 3 clock_time : 590106798  

and so on…

I’m wondering why the clock_time() is not returning the correct value of count. Does anyone know what I’m doing wrong?

Answer 1

Have you try with a wait between:

    printf("MAIN:count = %lu clock_time %lu",count, clock_time());
    wait(1000);
    flag = 0;

Maybe the clock is very fast and the units of your variable are too small to represent it. Or probaly the conversion in the printf of the variable type.