PWM output from PIC 16f877

MikroC gives us a very simple PWM library with 4 functions shown below:

• Pwm_Init()
• Pwm_Change_Duty()
• Pwm_Start()
• Pwm_Stop()

The expalanation of these function is as; The pwm_init() is used for initializing PWM which takes a argument of frequency in hertz
To Initialize a PWM module at 4KHz do this :Pwm_Init(4000), in this project it is used to get frequency of just 100 HZ at 1Mhz crystal. So i do this by putting value:Pwm_Init(400),
Pwm_Start() and Pwm_Stop() are used for starting and stopping PWM from micro-controller PIC16f877 or PIC 16f877A .pwm_init() to get two ouputs in 16f877
Pwm_Change_Duty() Changes PWM duty ratio. Parameter duty takes values from 0 to 255. It can be calculate using equation (Percent*255)/100. See 0 is used for 0%, 127 is used for 50%, and 255 is used for 100% duty ratio. In this project i am using two PWM outputs from PIC16f877, for user digital inputs to change the duty cycle ratio on real time, i am using two ports of micro-controller. It is just a simple project to understand the operation of PWM, and to understand its working. In this project to measure frequency real time, two counter timer are also used. To monitor the wave form of the pulses real time oscilloscope is also used. As shown in the figures below.
Pulse width modulation PWM code written in c language and to be compiled in MikroC is as below.pwm_init() to get 2 ouputs in 16f877
void main() {

OPTION_REG = 0x80;
// pull up resistors
PORTD = 255;
TRISD = 255;
PORTB = 255;
TRISB = 255;
PORTC = 0x0;
TRISC = 0;
// initialize PWM1 module
PWM1_Init(400);
// initialize PWM2 module
PWM2_Init(400);
PWM1_Start();
PWM2_Start();
while(1)
{
// set new PWM1 pattern ratio,
PWM1_Change_Duty(PORTb);
PWM2_Change_Duty(PORTD);
// set new PWM2 pattern ratio,
}
}