/******************************************************
      PIC16F877 - UP / DOWN Duty Cycle PWM1 Control 
*******************************************************/
#include <16f877.h>     // 
#use delay (clock=4000000) // 
int16  i=5; // declare a variable 

/********* Main function *******/

void main ( )
{
   setup_ccp1(CCP_PWM);  // setup CCP1 in PWM mode 
   setup_ccp2(CCP_PWM);  // setup CCP2 in PWM mode 

   setup_timer_2(T2_DIV_BY_16,170,1); // setup Timer2 

   set_pwm1_duty(i); // set PWM1 on base of variable i 
   set_pwm2_duty(i); // set PWM2 on base of variable i

   while(true) // endless loop 
   {
      if (input(pin_a0)) // test increasing button at RA0 
      {
         delay_ms(20);   // Button Debouce 
         while(input(pin_a0)); // Wait for button depressed 
         i+=3; // i=i+3 increase 3 steps each time , full range from 0-1024 ,but :.

         if (i>=170) // i maximum increasing value = 170 , 
            i=170;

         set_pwm1_duty(i); // set PWM1 
         set_pwm2_duty(i); // set PWM2 
      }

      if (input(pin_a1)) // test decreasing button at RA1 
      {
         delay_ms(20);  // Buton Debounce 
         while(input(pin_a1)); // Wait for button depressed
         i-=3;  // i=i-3 increase 3 steps each time , full range from 0-1024 , but : 

         if (i<5) // i minimum decreasing value = 5 
            i=5;

         set_pwm1_duty(i); // set PWM1 
         set_pwm2_duty(i); // set PWM2 
      }
   }
}

/******************************************************
      PIC16F877 PWM MODE Variable tone 
*******************************************************/
#include <16F877.h>     
#use delay (clock=4000000) 

int16  i=65; // Initial tone 

/********* Main Function********/

void main ( )
{
   
   setup_ccp1(CCP_PWM);  // 
   setup_timer_2(T2_DIV_BY_16,i,1); // 
   set_pwm1_duty(50); // 

   while(1) // 
   {
      if (input(pin_a0)) // 
      {
         delay_ms(20);         // 
         while(input(pin_a0)); // 
         i+=5; // i=i+5 .

         if (i>250) // 
            i=250;
         setup_timer_2(T2_DIV_BY_16,i,1); // 
      }

      if (input(pin_a1)) // 
      {
         delay_ms(20);         // 
         while(input(pin_a1)); // 
         i-=5;  // i=i-5 .

         if (i<65) // 
            i=65;
         setup_timer_2(T2_DIV_BY_16,i,1); // 
      }
   }
}