The CCP module is available with a number of dsPIC30/33 and PIC24 MCUs. mikroC PRO for dsPIC30/33 and PIC24 provides a library which simplifies using of the PWM HW Module.

  Important : PWM module uses either Timer2 or Timer3 module.

Library Routines

• PWM_Init
• PWM_Set_Duty
• PWM_Start
• PWM_Stop

PWM_Init

// Initializes the PWM module at 5KHz, channel 1, no clock prescale, timer2 :
unsigned int pwm_period1;
...
pwm_period1 = PWM_Init(5000, 1, 0, 2);

PWM_Set_Duty

// Set channel 1 duty ratio to 50%:
unsigned int pwm_period1;
...
PWM_Set_Duty(pwm_period1/2, 1);

PWM_Start

// start PWM at channel 1
PWM_Start(1);

PWM_Stop

// stop PWM at channel 1
PWM_Stop(1);

Library Example

The example changes PWM duty ratio on channels 1 and 2 continuously. If LEDs are connected to channels 1 and 2, a gradual change of emitted light will be noticeable.

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unsigned int current_duty, old_duty, current_duty1, old_duty1;
unsigned int pwm_period1, pwm_period2;

void InitMain() {
  ADPCFG = 0xFFFF;                           // Configure AN pins as digital I/O
  TRISB = 0xFFFF;                            // configure PORTB pins as input
  PORTD = 0;                                 // set PORTD to 0
  TRISD = 0;                                 // designate PORTD pins as output
}

void main() {
  InitMain();
  current_duty  = 16;                        // initial value for current_duty
  current_duty1 = 16;                        // initial value for current_duty1

  pwm_period1 = PWM_Init(5000 , 1, 1, 2);
  pwm_period2 = PWM_Init(10000, 2, 1, 3);

  PWM_Start(1);
  PWM_Start(2);

  PWM_Set_Duty(current_duty,  1);            // Set current duty for PWM1
  PWM_Set_Duty(current_duty1, 2);            // Set current duty for PWM2

  while (1) {                                // endless loop
    if (RB0_bit) {                           // button on RB0 pressed
      Delay_ms(20);
      current_duty++;                        // increment current_duty
      if (current_duty > pwm_period1) {      // if we increase current_duty greater then possible pwm_period1 value
        current_duty = 0;                    // reset current_duty value to zero
      }
      PWM_Set_Duty(current_duty,  1);        // set newly acquired duty ratio
     }

    if (RB1_bit) {                           // button on RB1 pressed
      Delay_ms(20);
      current_duty--;                        // decrement current_duty
      if (current_duty > pwm_period1) {      // if we decrease current_duty greater then possible pwm_period1 value (overflow)
        current_duty = pwm_period1;          // set current_duty to max possible value
      }
      PWM_Set_Duty(current_duty,  1);        // set newly acquired duty ratio
     }

    if (RB2_bit) {                           // button on RB2 pressed
      Delay_ms(20);
      current_duty1++;                       // increment current_duty1
      if (current_duty1 > pwm_period2) {     // if we increase current_duty1 greater then possible pwm_period2 value
        current_duty1 = 0;                   // reset current_duty1 value to zero
      }
      PWM_Set_Duty(current_duty1,  2);       // set newly acquired duty ratio
     }

    if (RB3_bit) {                           // button on RB3 pressed
      Delay_ms(20);
      current_duty1--;                       // decrement current_duty1
      if (current_duty1 > pwm_period2) {     // if we decrease current_duty1 greater then possible pwm_period1 value (overflow)
        current_duty1 = pwm_period2;         // set current_duty to max possible value
      }
      PWM_Set_Duty(current_duty1,  2);
     }

    Delay_ms(5);                             // slow down change pace a little
  }
}

HW Connection

PWM demonstration

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