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Is CCP_PWM too fast for an RC servo?

 
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weg22



Joined: 08 Jul 2005
Posts: 91

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Is CCP_PWM too fast for an RC servo?
PostPosted: Tue Apr 18, 2006 1:16 pm     Reply with quote
Hi all,

I am now trying to use the CCP pin to generate a PWM signal (as opposed to the INT_TIMER0 in my last post). However, I think the frequency needed to control an RC servo (a 20 ms period = 50 Hz) isn't feasible with my 10 MHz oscillator. The code below generates a 625 Hz PWM signal, but I need 50 Hz for it to work. Does anyone know of a workaround for this (without swapping my crystal)?

Thanks in advance,
weg

Code:

include <16F877.H>
#include <stdlib.h>
#include <math.h>

#define LED PIN_C0

#fuses HS,NOWDT,NOPROTECT,PUT,NOLVP
#use delay(clock=10000000)

void main()
{
   
   output_high(LED); delay_ms(1500);
   output_low(LED); delay_ms(1500);
   
   // setup PWM output
   setup_ccp1(CCP_PWM); // pwm output
   setup_timer_2(T2_DIV_BY_16, 255, 1);

   while(1)
   {
        output_high(LED);
      set_pwm1_duty(5);
   }
}
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue Apr 18, 2006 1:31 pm     Reply with quote
See this thread for a low frequency software PWM example:
http://www.ccsinfo.com/forum/viewtopic.php?t=20050
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