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Using Hardware Interrupt (INT0)

 
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ericzuki



Joined: 24 Feb 2004
Posts: 3

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Using Hardware Interrupt (INT0)
PostPosted: Mon Mar 08, 2004 9:41 am     Reply with quote
Hi All

I have written a test program on INT0 but I am not able to test it out on the hardware yet due to unavalibility. Can someone be kind enough to tell me whether the code will works.

A push button is connected to Pin B0 which when pushed will caused the chip to go into SLEEP mode. A second push on the pushbutton will bring the chip active and reset via reset_cpu().


Code:

#include <18F458.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)

// global flag to send processor into sleep mode
short sleep_mode;

// external interrupt when button pushed and released
#INT_EXT
void ext_isr()
{
   if(button_pressed_once)                // if button action and was not
                                                      // pressed
   {
      button_pressed_once=FALSE;    //to activate the next button pressed
                                                     // which is to reset the thing
      sleep();
   }
   else                         
   {
      button_pressed_once=TRUE;   // the button is now up
      reset_cpu();
   }
}

void main()
{

   ext_int_edge(H_TO_L);      // init interrupt triggering for button press
   enable_interrupts(INT_EXT);// turn on interrupts
   enable_interrupts(GLOBAL);

   static short button_pressed_once=TRUE;
}



Thanks
jds-pic



Joined: 17 Sep 2003
Posts: 205

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Re: Using Hardware Interrupt (INT0)
PostPosted: Mon Mar 08, 2004 9:09 pm     Reply with quote
ericzuki wrote:


Code:

#INT_EXT
void ext_isr()
{
   if(button_pressed_once)                // if button action and was not
                                                      // pressed
   {
      button_pressed_once=FALSE;    //to activate the next button pressed
                                                     // which is to reset the thing
      sleep();
   }
   else                         
   {
      button_pressed_once=TRUE;   // the button is now up
      reset_cpu();
   }
}

void main()
{

   ext_int_edge(H_TO_L);      // init interrupt triggering for button press
   enable_interrupts(INT_EXT);// turn on interrupts
   enable_interrupts(GLOBAL);

   static short button_pressed_once=TRUE;
}





it may just be me but i don't like the idea of going to sleep inside an interrupt handler function. i believe that this is asking for debugging troubles and it's just not good programming practice. why not just set a flag in #int_ext and test it in main()? keep your inerrupt handlers simple.

jds-pic
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