frequency counter using PIC's RTCC

[paranz]

since prescaler is 8-bit, the line

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frequency = ((unsigned long)get_timer0()<<8) + prescaler;

should be

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frequency = ((unsigned long)get_timer0()<<8) || prescaler;

but the actual 8-bit prescaler is not readable. Also, hindi ba fixed ang value ng prescaler (256)? Hindi na yata kailangan ang line na  prescaler--; sa loob ng do while loop

[paranz]

after, disabling the input you have to perform the self-clocking to read the prescaler value

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T0IF = 0;
while(!TOIF)
{
output_high(input_gate);
output_low(input_gate);
n++;
}

then followed by

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frequency = ((unsigned long)get_timer0()<<8) || (255 - n);
//display frequency to LCD


[paranz]

since prescaler is 8-bit, the line

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frequency = ((unsigned long)get_timer0()<<8) + prescaler;

should be

Code: [Select]

frequency = ((unsigned long)get_timer0()<<8) || prescaler;

but the actual 8-bit prescaler is not readable. Also, hindi ba fixed ang value ng prescaler (256)? Hindi na yata kailangan ang line na  prescaler--; sa loob ng do while loop

lolz mali pala, dapat

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frequency = ((unsigned long)get_timer0()<<8) | prescaler;
logical OR pala yun hehe 

[glutnix_neo]

sir paranz ok lang din yung "+",

I think many are confused between the prescaler na configurable sa timer peripheral(divide by n) against prescaler value. Imagine nyo na lang ang prescaler is simple binary counter yung ikinuconfigure natin eh kung saang output ng counter ikakabit ang input ng TMR0,

e.g. kung divide by 2 sa output ng 1st digit
divide by 4 sa output ng 2nd digit and so on.

pero yung counter, since counter xa eh may value din xa, yun yung iniaad natin sanakuha nating TMR0, kaya dapat fixed na devide by 256 ang configuration natin.makukuha natin ang value ng prescaler by self clocking then counting the number of pulses bago magincrement ang timer0 ng 1, then we use the formula 256 - # of pulses.

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while(true)
{
   //initialize
   prescaler_counter = 0;
   set_timer0(0);

   //getting TMR0 Value
   output_float(input_gate);          //enable input
   delay_ms(200);                       //gating time
   output_low(input_gate);           //disable input

   oldTMR0 = get_timer0();
   frequency = oldTMR0 * 256;  //pwede ring "frequency = oldTMR0 << 8;"
 
   //getting the prescaler value
   while(oldTMR0 == newTMR0)      //test if tmr0 has incremented
   {
      output_high(input_gate);       //self clocking
      output_low(input_gate);

      prescaler_counter++;            // count until TMR0 incremented

      newTMR0 = get_timer0();

   }
   frequency += (256 - prescaler_counter);
       
   display_reading();
}


['yus]

ah ok, ganun pala ang self-clocking.
pag-aralan ko muna kung ano'ng pinagkaiba nya dun sa code ko..

[glutnix_neo]

lagyan mo pala ng konteng nops
in between

 

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    output_high(input_gate);       //self clocking
      output_low(input_gate);
baka hindi makilala ng input.

['yus]

pwede na ang isang NOP?

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output_high(input_gate);       //self clocking
delay_cycles(1);                 // NOP  (4 osc clock)
output_low(input_gate);
delay_cycles(1); 

[glutnix_neo]

not sure check mo scope kung makikita mo tumaas yung output, kung hindi eh ibig sabihin kulang pa.

for testing gawin mo na marami muna.

['yus]

ganito nga pala yung setup ko ng timer0:

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setup_timer_0(RTCC_EXT_L_TO_H|RTCC_DIV_256);prescaler: divide by 256
trigger: external low-to-high

mas appropriate yung low-to-high na trigger point keysa sa high-to-low 'no?

[zer0w1ng]

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//getting TMR0 Value
   output_float(input_gate);          //enable input
   delay_ms(200);                       //gating time
   output_low(input_gate);           //disable input


On this part, interrupts must be disabled for it may cause jitter and may add small errors on the reading.
Also, take note that delay_ms(200) may not be *ACCURATELY* 200ms and depends on the compiler.
You could do the delay in assembly and count the cycles manually.

[zer0w1ng]

pwede na ang isang NOP?

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output_high(input_gate);       //self clocking
delay_cycles(1);                 // NOP  (4 osc clock)
output_low(input_gate);
delay_cycles(1); 

This is OK.
NOPs are important if when changing the outputs fast using BSF/BCF as above.  This is due to PIC's inherent READ-MODIFY-WRITE problem.  On PIC18, this is not present if the LAT registers are used instead of setting the I/O directly.

[paranz]

lagyan mo pala ng konteng nops
in between

 

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    output_high(input_gate);       //self clocking
      output_low(input_gate);
baka hindi makilala ng input.

pwede na rin walang NOP, since the T0CKI can easily read even up to 50Mhz digital signal

sir paranz ok lang din yung "+",

oo nga pala. ty 

[paranz]

mas tama pala binigay na code ni glutnix sa self-clocking

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while(oldTMR0 == newTMR0)
hindi kasi pwede yung binigay ko na sa CCS C, for hitech lang yun hehe 

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while(!T0IF)

[glutnix_neo]

yup at saka hindi overflow aabangan natin kundi yung change (incerement by 1) sa timer0.

Well on the second thought overflow pa rin un, hehehe, overflow ng prescaler not the timer,hehehehe

[paranz]

yup at saka hindi overflow aabangan natin kundi yung change (incerement by 1) sa timer0.

Well on the second thought overflow pa rin un, hehehe, overflow ng prescaler not the timer,hehehehe

ah oo nga pala, you are correct 

hehe hidni ko napansin ah, basta overflow 

['yus]

paki-clarify naman nung table na nasa AN592 "Frequency Counter Using PIC16C5X"

tama ba yung nasa last row nung table? typographical error? o ganyan talaga?

[glutnix_neo]

alam ko nacheck ko na dati assembly nito, tama po yan, as you may have notice way below clock frequency na ang input frequency, ibang method/technique ang ginamit nya pagsukat, aralin ko po ulet ha.

['yus]

.. tama po yan, as you may have notice way below clock frequency na ang input frequency, ibang method/technique ang ginamit nya pagsukat..

ah ok.. kala typo error lang.. hehe 

   btw, glutnix_neo,
   masarap ba yung Fruitas shake na binili mo kaninang lunch time? 

[glutnix_neo]

nyahahaha, kilala mo na ko ha, ako nakita kita minsan hindi ko matandaan kung sino,hehehe

['yus]

pa-check uli ng code ko.. nilagyan ko na ng auto-range..
ok naman, automatic na nagbabago na ang kanyang range,
pero di ko sure kung ito ang pinaka-efficient:

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while(true)
   {
      prescaler_counter = 0;
      oldTMR0 = get_timer0();
      sprintf(str2," Hz");
      if(get_pulses(1)==0)
      {
         if(get_pulses(5)==0)
         {
            if(get_pulses(50)==0)
            {
               if(get_pulses(200)==0)
               {
                  oldTMR0 = get_pulses(1000);
               }
               else{ oldTMR0 = get_pulses(200); sprintf(str2," Khz100to10"); }
            }
            else{ oldTMR0 = get_pulses(50); sprintf(str2," Khz1Kto100"); }
         }
         else{ oldTMR0 = get_pulses(5); sprintf(str2," Mhz10to1"); }
      }
      else{ oldTMR0 = get_pulses(1); sprintf(str2," Mhz50to10"); }
           
      do
      {
         output_high(input_gate);       //self clocking
         delay_cycles(1);
         output_low(input_gate);
         delay_cycles(1);
         prescaler_counter++;            // count until TMR0 incremented
      }while( get_timer0()==oldTMR0 && prescaler_counter<=256); 
      frequency = ((unsigned long)oldTMR0<<8) + (256 - prescaler_counter) - 1;
     
   display_reading();
   }


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unsigned int get_pulses(unsigned char gate_time)
{
   set_timer0(0);
   output_float(input_gate);
   delay_ms(gate_time);
   output_low(input_gate);
   return get_timer0();
}
di ko muna nilagay yung technique for measuring frequency at the lowest range..