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Generating PWM with PIC Microcontroller using CCP Module

PIC16F877A

PWM is a technique used to generate analog output signal using digital signals. It is commonly used to control average power delivered to a load, motor speed control, generating analog voltage levels and for generating analog waveforms.

CCP Modules are available with a number of PIC Microcontrollers. CCP stands for Capture/Compare/PWM. Using PWM module is far more easier and cost effective than using extra chips for PWM generation.  MikroC Pro for PIC Microcontroller provide built-in library for PWM which makes our task very simple.

MikroC Functions

Note 1 :  For microcontrollers with more than one CCP module, to use the desired CCP module for PWM generation simply change the number “1”  in the prototype with desired module number. eg: PWM2_Init(5000), PWM2_Start().

Note 2 : All PWM modules in a PIC Microcontroller uses Timer 2 for its operation, so you cannot set different frequencies for different PWM modules.

In this tutorial we are using PIC 16F877A for demonstrating PWM generation using CCP module. PIC 16F877A contains two CCP modules.

Circuit Diagram – Using internal PWM Module of PIC

In the below circuit four switches are provided for controlling the Duty Ratio of PWM generated by two CCP modules of the PIC Microcontroller.

Using Internal PWM Module PIC Microcontroller Circuit Diagram

The output of the two CCP modules are given to a CRO to observe the changes in pulse width. It may be given to two LEDs and you can see the changes in brightness as Duty Ratio changes.

MikroC Program

void main()
{
  short current_duty_1  = 16; // initial value for current_duty_1
  short current_duty_2 = 16;  // initial value for current_duty_2

  TRISD = 0xFF; // PORTD as input
  TRISC = 0x00; // PORTC as output

  PWM1_Init(5000);  // Initialize PWM1
  PWM2_Init(5000);  // Initialize PWM2

  PWM1_Start();  // start PWM1
  PWM2_Start();  // start PWM2

  PWM1_Set_Duty(current_duty_1); // Set current duty for PWM1
  PWM2_Set_Duty(current_duty_2); // Set current duty for PWM2

  while (1)        // endless loop
  {
     if (!RD0_bit)   // if button on RD0 pressed
     {
      Delay_ms(40);
      current_duty_1++;  // increment current_duty_1
      PWM1_Set_Duty(current_duty_1);  //Change the duty cycle
     }

    if (!RD1_bit)               // button on RD1 pressed
    {
      Delay_ms(40);
      current_duty_1--;  // decrement current_duty_1
      PWM1_Set_Duty(current_duty_1);
     }

    if (!RD2_bit)     // if button on RD2 pressed
    {
      Delay_ms(40);
      current_duty_2++;    // increment current_duty_2
      PWM2_Set_Duty(current_duty_2);
     }

    if (!RD3_bit)       // if button on RD3 pressed
    {
      Delay_ms(40);
      current_duty_2--;   // decrement current_duty_2
      PWM2_Set_Duty(current_duty_2);
     }

    Delay_ms(10);      // slow down change pace a little
  }
}

I thinks the program is self explanatory, so if you have any doubts please comment below…

Download

You can download the MikroC Source Code, Proteus files etc here…

Video