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WDT on a PIC12F635

 
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Tagge



Joined: 23 Aug 2005
Posts: 93

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WDT on a PIC12F635
PostPosted: Tue Oct 11, 2011 5:57 am     Reply with quote

Hi, I'm having trouble to get the WDT to work on a 12F635. What am I doing wrong?
Code:

#FUSES WDT                        //WDT on
#FUSES INTRC_IO                 //Internal RC Osc, no CLKOUT
#FUSES NOPROTECT                //Code not protected from reading
#FUSES NOCPD                    //No EE protection
#FUSES MCLR                     //Master Clear pin enabled
#FUSES IESO                     //Internal External Switch Over mode enabled
#FUSES PUT                      //Power Up Timer
#FUSES FCMEN                    //Fail-safe clock monitor enabled
#FUSES NOWURE                   //Wake-up and continue
#FUSES BROWNOUT                 //Reset when brownout detected
#use delay(clock=31000, restart_wdt)


void init(void){
   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_32); 
   setup_wdt(WDT_2304MS);
   setup_timer_1(T1_DISABLED);
   setup_comparator(NC_NC);
   setup_vref(FALSE);
   enable_interrupts(INT_TIMER0);
   enable_interrupts(GLOBAL);
   setup_oscillator(OSC_31KHZ);
   }
then in main
while(1){   
      restart_wdt();
      do my thing..
}

Where's the stupidity of mine? Smile
Ttelmah



Joined: 11 Mar 2010
Posts: 19539

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PostPosted: Tue Oct 11, 2011 7:03 am     Reply with quote

It might help if you told us what is wrong....

However, key thing with most of the smaller PIC's, is that parts of the prescaler are _shared_ between Timer0, and the WDT. So changing one affects the other. So selecting WDT_2304MS, will set the RTCC prescaler to RTCC_DIV_256. Use the watchdog _postscaler_ instead, which can be independently set.

Best Wishes
Tagge



Joined: 23 Aug 2005
Posts: 93

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PostPosted: Tue Oct 11, 2011 7:58 am     Reply with quote

Thanks, its just the problem.. you nailed it exactly. It seems that the timer 0 is depending on the WDT scaler.
This seems to get it working better.
Code:

void init(void){
   setup_wdt(WDT_18MS|WDT_TIMES_1);
   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_32);   
   setup_timer_1(T1_DISABLED);
   setup_comparator(NC_NC);
   setup_vref(FALSE);
   enable_interrupts(INT_TIMER0);
   enable_interrupts(GLOBAL);
   setup_oscillator(OSC_31KHZ);
   output_low(air_valve);//renblĂ„sning off 
   output_high(air_led);
}

/Tagge
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