50mhz Frequency counter

[ISAAC AIYANYO]

Hello Picstars
i need your help here.
i am trying to use the pic as a frequency counter using a 16F873 but i don't seems to have the example file
EX_FREQC.C even though its listed in the manual.
Would anyone be kind enough to post the program if you have it.
have anyone done anything like this before i need to measure the frequency of a square wave with a range of 100Hz to 10Khz
Any help rendered would be much appreciated

Isaac

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This message was ported from CCS's old forum
Original Post ID: 13708

[PCM programmer]

:=
:= Hello Picstars
:= i need your help here.
:= i am trying to use the pic as a frequency counter using a 16F873 but i don't seems to have the example file
:=EX_FREQC.C even though its listed in the manual.
:= Would anyone be kind enough to post the program if you have it.
:= have anyone done anything like this before i need to measure the frequency of a square wave with a range of 100Hz to 10Khz
:= Any help rendered would be much appreciated
:=
--------------------------------------------------------

By using Google I found it very quickly. <a href="http://www.google.com" TARGET="_blank">http://www.google.com</a>
Here are the files:
<a href="http://www.cc.puv.fi/~t0101190/projekti/source/Examples/" TARGET="_blank">http://www.cc.puv.fi/~t0101190/projekti/source/Examples/</a>
I notice that CCS doesn't have NOLVP in the #fuses statement.
They really should have it in there, because the average person
does not use LVP, and it causes a lot of problems if you
forget to set it for NOLVP.
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This message was ported from CCS's old forum
Original Post ID: 13712

[Hans Wedemeyer]

without prescaler I the pic can't count at 50 mega Hertz.
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This message was ported from CCS's old forum
Original Post ID: 13719

[isaac aiyanyo]

Thank you every much for the link
its very much appreciated.
i have ran the program but i am still very confused
with the results i am getting as could understand why parts of the program were commented out?
i want to use it for the frequency range 100Hz to 10Khz
but i am getting the following results

AT 100Hz i get 11000Hz to 12000Hz
AT 1KHz i get about 13870Hz
AT 100KHz i get about 27000Hz

Could someone please tell me where i am going wrong
my program is below
Hope to hear from you soon
Isaac
#if defined(__PCM__)
#include <16F876.H>
#fuses HS,NOWDT,NOPUT,NOPROTECT,NOBROWNOUT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7,RESTART_WDT,ERRORS)
#bit t1_overflow=0x0C.0


// #bit t1_overflow=0xF9E.0 (PIC18, Reminder)

void main() {
int cycles8, cycles;
int32 freq;
long freqc_high;
long freqc_low;

while (TRUE) {
cycles8=0;
cycles=0;
freqc_high=0;
t1_overflow=0;
set_timer1(0);
setup_timer_1(T1_EXTERNAL|T1_DIV_BY_1);
/* ___ wait one second ___ */
while (cycles!=0xFF) { //true=3, false=4
cycles8=0; //1 cycle
//start inner loop
while (cycles8!=0xFF) { //true=3, false=4
if (t1_overflow)//true=2,false=3 //----|
{t1_overflow=0;freqc_high++;}//6 cycles // |
else // |-- 8 cycles
{delay_cycles(5);} //----|
delay_cycles(62); //x
cycles8++; //1
///2 cycles to jump to top
//math: end inner loop
//math: total inner loop=((3+8+x+1+2)*255 + 4)*255
//math: if x=62.87781 then inner loops takes 5mil instructions
//math: if x=62 then inner loop takes 4942920, have to fill 57080 cycles
}
delay_cycles(216); //y
cycles++; ///1 cycle
///2 cylces to jump to top
//math: outer=(3+1+y+1+2)*255+4=57080
//math: y=(57080-4)/255)-(3+1+0+0+1+2)
//math: if y=216.827450980392156862745098039216 then outer loop cylces is 57080
//math: if y=216 then outer loop cycles is off by 211 cycles. z=211
}
delay_cycles(211); //z
/* ___ end waiting 1 second ___ */
setup_timer_1(T1_DISABLED); //turn of counter to prevent corruption while grabbing value
if (t1_overflow) //check one last time for overflow
freqc_high++;
freqc_low=get_timer1(); //get timer1 value as the least sign. 16bits of freq counter
freq=make32(freqc_high,freqc_low); //use new make32 function to join lsb and msb
printf("\%LU Hz\r\n",freq); //and print frequency

}
}


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This message was ported from CCS's old forum
Original Post ID: 13757

[Mike Broom]

Below is a simple interrupt driven frequency counter which will work between approx 1Hz to 65.5kHz

Mike

[inmelody]

hi can you send me proteus schematic for this frequency counter. I try but i cant do it :( ...

[temtronic]

I seriously doubt anyone here will send you a Proteus schematic.
We all KNOW Proteus is full of bug,errors and faulty DRCs and as such is a complete waste of time.

Please read PIC101 thread...


Also note that ANY floating point math takes a LOT of time on PICs, so if your signal source is not stable, you'll see 'funny' numbers.

hth
jay

[dyeatman]

inmelody,
Do you realize this thread is right at 10 YEARS old? I doubt that user is still in the forum any more
_________________
Google and Forum Search are some of your best tools!!!!

[ckielstra]

[Ttelmah]

There is though the problem that the multi-byte 'frequency' value will change during the calculation. So abnormal results would be the 'norm' (if you see what I mean....).

Best Wishes

[ckielstra]