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I need help with two interrupts

 
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nick_18



Joined: 22 May 2010
Posts: 2

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I need help with two interrupts
PostPosted: Sat May 22, 2010 1:40 am     Reply with quote
hi I'm a newby programing in CCS and I have a problem, but first sorry for my bad english and I hope you understand.
Ok. I use the timer0 to control a countdown timer (00 to 99) that show in two 7 segment. I use the timer2 to set a pwm at 64khz. The problem is when both interrupts are enabled (the pwm and the countdown timer), the seven segment display begin flashing and the pic crash, pic stops responding and for example I can not use the buttons for setting the time.
Thanks for your help.

Here is the code and Proteus simulation.
Code:


#include<16F876A.h>
#fuses XT,NOPUT,NOWDT,NOLVP,NOPROTECT
#use delay(clock=8000000)
#byte TRISA=0x85
#byte TRISB=0x86
#byte TRISC=0x87
#byte PORTA=0x05
#byte PORTB=0x06
#define max_duty 124

signed int  d1,d2;
int16 duty_cicle;
long overflow;

                                                  // array with numbers 0 to 9
int show[]={0b00111111,0b00000110,0b01011011,0b01001111,
            0b01100110,0b01101101,0b01111101,0b00000111,   
            0b01111111,0b01100111};


void config(void){
      TRISA=0x00;
      TRISB=0x00;
      TRISC=0x00;
      setup_timer_0(RTCC_INTERNAL|RTCC_DIV_16|RTCC_8_BIT);
      setup_timer_2(T2_DIV_BY_1,30,1);
      set_timer0(214);
     
}

void reset(void){
disable_interrupts(GLOBAL);
disable_interrupts(INT_RTCC);
disable_interrupts(INT_TIMER1);
}

#INT_RTCC
void RTCC(){
        //countdown
  overflow++;
 
  if(overflow>10000){ overflow=0; D2--;}
  if(D2<0){D2=9;D1--;}
  if(d1==0 && d2==0){break; reset();}
 
  set_timer0(214);
}

#int_timer2
void timer2_isr(void)     //PWM
{
static int8 increment = TRUE;

if(increment)
  {                                           
   duty_cicle++;

   if(duty_cicle == max_duty){
      increment = FALSE;
                                             
   }
  }
else
  {
   duty_cicle--;
     
   if(duty_cicle == 0)
      increment = TRUE;
     
   }   
set_pwm1_duty(duty_cicle);

}



void main()
{
disable_interrupts(global);
disable_interrupts(INT_RTCC);
disable_interrupts(INT_TIMER1);
disable_interrupts(INT_TIMER2);
config();

for(;;){


if(input(pin_a5)){ if(d1!=0 || d2!=0){     //pin_a5 button to begin the count time and pwm
      delay_ms(60);
      enable_interrupts(GLOBAL);
      enable_interrupts(INT_RTCC);
      enable_interrupts(INT_timer2);
      setup_ccp1(CCP_PWM);
      }}
                 
if(input(PIN_A3)){                         //Increase time
      delay_ms(60);                 
      D2++;
        if(D2>=10){ D2=0; D1++;}
         if(D1>9){D1=0;D2=0;}
      }
     
if(input(PIN_A4)){if(d1!=0 || d2!=0){      //decrease time
      delay_ms(60);
      D2--;
      if(D2<0){ D2=9; D1--;}
      if(D1<0){D1=0;D2=0;}
      }}               
                 
               output_high(pin_a1);    // show time in display
               PORTB=show[D1];
               output_low(pin_a0);
               delay_ms(10);
               output_high(pin_a0);
               PORTB=show[D2];
               output_low(pin_a1);
               delay_ms(10);     
 }
 
}

The Proteus simulation is here

http://rapidshare.com/files/390237258/test.rar
bkamen



Joined: 07 Jan 2004
Posts: 1615
Location: Central Illinois, USA

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PostPosted: Sat May 22, 2010 2:53 pm     Reply with quote
For timer2, if all you want is just pure pwm that doesn't change in any sort of time crticial way, you don't need to enable the interrupt. Just set the timer to run and your period values and the PWM will operate.

The only "interrupt" you need to really service is timer0.
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Ttelmah



Joined: 11 Mar 2010
Posts: 19505

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PostPosted: Sat May 22, 2010 3:01 pm     Reply with quote
First a small problem. XT fuse selected. Max frequency recommended for this fuse, 4MHz....
Then, a comment. You select RTCC as 8bit, but the 876, _only_ has an 8bit RTCC. This option does nothing on this chip.

Your big problem is _time_.
The RTCC, is effectively counting in '8 instruction' ticks. You set it to 214. It'll then try to trigger every 336 instructions. Your Timer2 interrupt though, is set to reset at just 31 counts, and is counting in instructions. So, just 31 instructions between triggers. It takes typically 60 instructions to get into, and out of an interrupt. Add the code in the interrupt itself (perhaps another dozen instructions), and this interrupt will continuously trigger...
You need to slow down this interrupt to have any hope at all of the code working. The last value in the timer2 setup, is the number of PWM cycles between interrupt triggers, and is there just for this reason.
Realistically, drop the PWM to perhaps 20KHz, and interrup every fourth cycle, and you will have a 'chance'...

Best Wishes
nick_18



Joined: 22 May 2010
Posts: 2

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PostPosted: Sat May 22, 2010 5:13 pm     Reply with quote
Thank you very much for you help.
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