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Sleep and waking up

 
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Markdem



Joined: 24 Jun 2005
Posts: 206

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Sleep and waking up
PostPosted: Sat Jun 21, 2008 1:54 am     Reply with quote
Hi all, I am trying to put a PIC to sleep in int_rb. Problem is, it will not wake back up when the interrupt fires again. It looks like the ISR fires, as it will print "Power Fail" on the LCD. I have tried both on real hardware and in simulator, but both will not reset.

Code:

#include <18F4550.h>

#fuses HSPLL,NOWDT,NOPROTECT,NOLVP,NODEBUG,USBDIV,PLL5,CPUDIV1,VREGEN,BROWNOUT,NOMCLR
#use delay(clock=48000000)

#define POWER_FAIL_SENSE_PIN    PIN_B7   

#include "LCD420.c"

int16 count;

int1 PF = 0, do_ISR = 0;

#int_rb
void rb_isr()
   {
      if(!input(POWER_FAIL_SENSE_PIN))
         {   
            printf(lcd_putc,"\f");
            lcd_gotoxy(5,2);                  
            printf(lcd_putc,"Power Fail");

            PF = 1;
            sleep();
            delay_cycles(1);

         }

      if(input(POWER_FAIL_SENSE_PIN) && PF == 1)
         {
            reset_cpu();
         }

   }
   
void main()
   {
      lcd_init();
      printf(lcd_putc,"Running");


      enable_interrupts(GLOBAL);
   
      enable_interrupts(INT_RB);
      
      while(1)
         {
            count++;
            lcd_gotoxy(1,2);                  
            printf(lcd_putc,"count:%Lu",count);
            delay_ms(100);
         }
   }


I have also tried to set a flag inside void rb_isr(), but then the pic locks up before it prints out "Power Fail".

I have got debounce hardware on B7.

Can anyone help he out.

Thanks.
Humberto



Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata

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PostPosted: Sat Jun 21, 2008 10:48 am     Reply with quote
I never tryed, but according to the datasheet, a fixed delay is required when leaving Sleep
and Idle modes. The needed delay is for Oscillator Strt-up and the PLL lock time out.
The needed delay is only of a few machines cycles, hence 10 machines cycles inside
an interrupt would be enough.

Code:

#int_rb
void rb_isr()
   {
      delay_cycles(10);

      if(!input(POWER_FAIL_SENSE_PIN))
         {   
            printf(lcd_putc,"\f");
            lcd_gotoxy(5,2);                 
            printf(lcd_putc,"Power Fail");

            PF = 1;
            sleep();
            delay_cycles(1);

         }

      if(input(POWER_FAIL_SENSE_PIN) && PF == 1)
         {
            reset_cpu();
         }
   }


Humberto
Ttelmah
Guest
PostPosted: Sat Jun 21, 2008 2:39 pm     Reply with quote
Inside the ISR, the interrupt flag has _not_ been cleared. If you go to sleep with an interrupt flag already set, that interrupt, cannot wake you up.

You need:
Code:

            PF = 1;
            clear_interrupts(INT_RB);
            sleep();
            delay_cycles(1);

The 'clear', should be the last instruction before the interrupt.

Best Wishes
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