/* 
 Pulse Width Modulation 
  Description: CCP module generating a PWM signal 
 MCU: PIC16F628A 
 Oscillator: XT, 4.0 MHz, MCLR Enabled 
*/ 
 sbit UP at RB0_bit; 
 sbit DOWN at RB1_bit; 
 unsigned short new_DC, current_DC; 
 void debounce(){ 
  Delay_ms(300); 
 } 
 void main() { 
 CMCON = 0x07; // Disable comparators 
 PORTB = 0x00; 
 TRISB = 0b00000011; // RB0, RB1 input, RB3 (PWM1) output 
 PWM1_Init(5000);    // PWM module initialization (5KHz) 
 new_DC = 0;         // Initial value of variable Duty Cycle 
 current_DC = 0; 
 PWM1_Start();       // Start PWM1 module with Zero DC 
 PWM1_Set_Duty(current_DC); 
 do { 
  if (!UP){      // If the button connected to RB0 is pressed 
   debounce(); 
   if (new_DC < 250)      // Don't go above 250 
   new_DC = new_DC + 25 ; // increment Duty Cycle by 25 
  } 
  if (!DOWN) {   // If the button connected to RB1 is pressed 
   debounce(); 
   if (new_DC !=0)        // Don't go below 0 
   new_DC= new_DC - 25 ; // Decrement Duty Cycle by 25 
} 
  if (current_DC != new_DC) { 
   current_DC = new_DC ; 
   PWM1_Set_Duty(current_DC); // Change the current DC to new value 
  } 
 } while(1); 
}  // END main()