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I need advice, multitasking goes out of synchronization

 
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Zloi



Joined: 26 Oct 2012
Posts: 11
Location: Croatia

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I need advice, multitasking goes out of synchronization
PostPosted: Fri Oct 26, 2012 12:05 pm     Reply with quote
I try to blink two led's in multitasking manner, but things are getting out of control, after n first cycle LED's are no longer synchronized. I'm using unsigned arithmetic and timer overflow should not be a problem. my guess is that the source of the error is IF conndition and > operator.
Can someone give me advice?

Here is code snippet,

Code:

#include <18F4620.h>
#device *=16
#fuses HS,NOWDT,NOPROTECT,NOLVP,BROWNOUT
#use delay(crystal=10Mhz, clock=40Mhz)
#use rs232(baud=57600, xmit=PIN_C6, rcv=PIN_C7, parity=N, bits=8, ERRORS)
#USE FAST_IO (ALL)
#include <string.h>

#define RedTimeToggle 500


#INT_TIMER0
void One_mS_Timer(void){                                 
   set_timer0(Timer0IntCnt);
   Int0Cnt++;                                 
   if(Int0Cnt>19){
      Int0Cnt=0;                              
      Mills++;
   }


struct {                     
.
.
.
unsigned int16 Old_Red_Mills;
.
.   
} Left,Right;





unsigned int16 CalcElapsedTime(unsigned int16 MillsC,unsigned int16 OldMills){      
unsigned int16 calc;
   calc=MillsC - OldMills;
return (calc);
}


void LeftStartCondErr(){
   if (CalcElapsedTime(Mills,Left.Old_Red_Mills) > (unsigned int16)(RedTimeToggle)){
   printf("Left=%lu\r\n",Mills-Left.Old_Red_Mills);
   printf("Mils=%lu\r\n"Mills);
      Left.Old_Red_Mills=Mills;
      if (input_state(LR)){            
         output_low(LR);
         }
      else{
         output_high(LR);
      }

   
}


void RightStartCondErr(void){
   if (CalcElapsedTime(Mills,Right.Old_Red_Mills) > RedTimeToggle){
   Right.Old_Red_Mills=Mills;
      if (input_state(RR)){               
         output_low(RR);

         }
      else{
         output_high(RR);
         
      }
   
}





void main(void){
   main:
   disable_interrupts(GLOBAL);
   SystemInit();
   OutputInit();
   SystemVariableInit();
   FlushBuffers();
   set_pwm1_duty(514);      
   enable_interrupts(INT_TIMER0);
   enable_interrupts(INT_RDA);
   enable_interrupts(GLOBAL);
   set_timer0(Timer0IntCnt);          
   printf("\r\n Running....\r\n");
   output_low(PIN_A1);
        Mills=0;   
        LoopTime=Mills;
        Right.Old_Red_Mills=Left.Old_Red_Mills=Mills;
 
      while (true){
           LeftStartCondErr();
           RightStartCondErr();
        }





Here is the Printout:.
Mils=56135
Left=501
Mils=56638
Left=193 -> passed to the comparison condition
Mils=56833
Left=501
Mils=57336
Left=501
Mils=57839
Left=501
Ttelmah



Joined: 11 Mar 2010
Posts: 19509

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PostPosted: Fri Oct 26, 2012 1:18 pm     Reply with quote
Unfortunately,what you post, is a messy bit of tatty code, missing vital parts, and too large for debugging. But some comments:

Remember your printf's,will take about 4mSec.
Remember anything reading or writing an int16, which is updated in an interrupt, needs to _disable_ the interrupt, read/write the value, and then re-enable the interrupt. Otherwise if the value updates between one byte being used and the other, the results _will_ be wrong. Then is is even worse with something slow like a printf.....
Zloi



Joined: 26 Oct 2012
Posts: 11
Location: Croatia

View user's profile Send private message

PostPosted: Fri Oct 26, 2012 4:10 pm     Reply with quote
Ttelmah wrote:
Unfortunately,what you post, is a messy bit of tatty code, missing vital parts, and too large for debugging.

I agree with the comment, program has about 800 lines of code and counting, for purposes of readability I did not want to post everything.
problem with LEDs haunted me for days.

Ttelmah wrote:

But some comments:

Remember your printf's,will take about 4mSec.
Remember anything reading or writing an int16, which is updated in an interrupt, needs to _disable_ the interrupt, read/write the value, and then re-enable the interrupt. Otherwise if the value updates between one byte being used and the other, the results _will_ be wrong. Then is is even worse with something slow like a printf.....


printf were there just for "debugging"...
I tried with disabling interrupts, but without positive result.
btw this is good advice with guarding int6,32 by disabling interrupts.

In the end I set up a free timer3 in main,

Code:

void GetTime(void){
if(get_timer3()>1249){
   set_timer3(0);      
   Mills++;
   }
}


So far everything working as expected.

Best regards
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