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Problem updating variable in ISR

 
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ccowley



Joined: 12 Sep 2009
Posts: 19

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Problem updating variable in ISR
PostPosted: Fri May 03, 2013 11:33 am     Reply with quote
I am not an experienced C programmer and I am trying to get some code to decrement a variable every time the ISR is run. The first routine below works, so I know the ISR is working, but the second routine doesn't seem to do anything. It should be decrementing my LED display that is connected to port_C. It might just be that I still don't quite get global variables (along with other things). Any help would be appreciated!

Code:
#include <main.h>
#int_EXT

//int x=255;

void  EXT_isr(void)
{
   Output_C(255);
//   x--;
   delay_ms(1000);

}



void main()
{
   int x;
   
   setup_lcd(LCD_DISABLED);
   enable_interrupts(INT_EXT);
   enable_interrupts(GLOBAL);
   ext_int_edge(H_to_L);
   setup_oscillator(OSC_8MHZ);

   while(TRUE)
   {
      output_C(x);
      x++;
      delay_ms(100);
   }

}


2nd code:

Code:
#include <main.h>
#int_EXT

int x=255;

void  EXT_isr(void)
{
//   Output_C(255);
   x--;
   delay_ms(1000);

}



void main()
{
   int x;
   
   setup_lcd(LCD_DISABLED);
   enable_interrupts(INT_EXT);
   enable_interrupts(GLOBAL);
   ext_int_edge(H_to_L);
   setup_oscillator(OSC_8MHZ);

   while(TRUE)
   {
      output_C(x);
//      x++;
      delay_ms(100);
   }

}
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri May 03, 2013 11:55 am     Reply with quote
Quote:
#include <main.h>
#int_EXT

int x=255;

void EXT_isr(void)
{
// Output_C(255);
x--;
delay_ms(1000);

}

The #int_xxx directive must be placed just above the interrupt routine.
See this post::
http://www.ccsinfo.com/forum/viewtopic.php?t=46477&start=4
ccowley



Joined: 12 Sep 2009
Posts: 19

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Thank you! That worked!
PostPosted: Fri May 03, 2013 1:35 pm     Reply with quote
Thanks for the help! That worked perfectly. I also had to get rid of the "int x;" that was in MAIN, but that was just a holdover from the previous program I forgot to change before I posted.

Thanks again!
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