PWM Library

CCP module is available with a number of PIC MCUs. mikroC PRO for PIC provides library which simplifies using PWM HW Module.

  Important :

Library Routines

PWM1_Init

Prototype

void PWM1_Init(const long freq);

Returns

Nothing.

Description

Initializes the PWM module with duty ratio 0. Parameter freq is a desired PWM frequency in Hz (refer to device data sheet for correct values in respect with Fosc).

This routine needs to be called before using other functions from PWM Library.

Requires

MCU must have CCP module.

  Note : Calculation of the PWM frequency value is carried out by the compiler, as it would produce a relatively large code if performed on the library level.
Therefore, compiler needs to know the value of the parameter in the compile time. That is why this parameter needs to be a constant, and not a variable.
Example

Initialize PWM module at 5KHz:

PWM1_Init(5000);

PWM1_Set_Duty

Prototype

void PWM1_Set_Duty(unsigned short duty_ratio);

Returns

Nothing.

Description

Sets PWM duty ratio. Parameter duty takes values from 0 to 255, where 0 is 0%, 127 is 50%, and 255 is 100% duty ratio. Other specific values for duty ratio can be calculated as (Percent*255)/100.

Requires

MCU must have CCP module. PWM1_Init must be called before using this routine.

Example

Set duty ratio to 75%:

PWM1_Set_Duty(192);

PWM1_Start

Prototype

void PWM1_Start(void);

Returns

Nothing.

Description

Starts PWM.

Requires

MCU must have CCP module. PWM1_Init must be called before using this routine.

Example
PWM1_Start();

PWM1_Stop

Prototype

void PWM1_Stop(void);

Returns

Nothing.

Description

Stops PWM.

Requires

MCU must have CCP module. PWM1_Init must be called before using this routine. PWM1_Start should be called before using this routine, otherwise it will have no effect as the PWM module is not running.

Example
PWM1_Stop();

Library Example

The example changes PWM duty ratio on RC1 and RC2 pins continually. If LED is connected to these pins, you can observe the gradual change of emitted light.

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unsigned short current_duty, old_duty, current_duty1, old_duty1;

void InitMain() {
  ANSEL  = 0;                         // Configure AN pins as digital
  ANSELH = 0;
  C1ON_bit = 0;                       // Disable comparators
  C2ON_bit = 0;
  
  PORTA = 255;
  TRISA = 255;                        // configure PORTA pins as input
  PORTB = 0;                          // set PORTB to 0
  TRISB = 0;                          // designate PORTB pins as output
  PORTC = 0;                          // set PORTC to 0
  TRISC = 0;                          // designate PORTC pins as output
  PWM1_Init(5000);                    // Initialize PWM1 module at 5KHz
  PWM2_Init(5000);                    // Initialize PWM2 module at 5KHz
}

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

  PWM1_Start();                       // start PWM1
  PWM2_Start();                       // start PWM2
  PWM1_Set_Duty(current_duty);        // Set current duty for PWM1
  PWM2_Set_Duty(current_duty1);       // Set current duty for PWM2

  while (1) {                         // endless loop
    if (RA0_bit) {                    // button on RA0 pressed
      Delay_ms(40);
      current_duty++;                 // increment current_duty
      PWM1_Set_Duty(current_duty);
     }

    if (RA1_bit) {                    // button on RA1 pressed
      Delay_ms(40);
      current_duty--;                 // decrement current_duty
      PWM1_Set_Duty(current_duty);
     }

    if (RA2_bit) {                    // button on RA2 pressed
      Delay_ms(40);
      current_duty1++;                // increment current_duty1
      PWM2_Set_Duty(current_duty1);
     }

    if (RA3_bit) {                    // button on RA3 pressed
      Delay_ms(40);
      current_duty1--;                // decrement current_duty1
      PWM2_Set_Duty(current_duty1);
     }

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

HW Connection

PWM demonstration

PWM demonstration

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