Basics:
To generate PWM(Pulse Width Modulation) both analog and digital circuits can be used. But using a micro-controller is much easier than other methods. To generate PWM, the micro-controller has a built-in PWM module. But if there is no such PWM module then how can you generate PWM? Yes, in this article we are going to learn how we can generate a PWM signal if there is no such module built-in. Let’s start!Usually, there is a built-in module in micro-controllers. But not all the micro-controllers have this feature. When there is such a module, you can not generate PWM using the built-in modules. But you can use some programming skills to generate a PWM signal.
Using timer interrupt, we can generate a PWM signal from any micro-controller. The method is very simple. First, use a timer interrupt to call interrupt say 100 times per second. Then, count each interrupt and set it zero at 100, besides creating a condition that until a duty (say 40 for 40%) the output is high, then the output is 0 until the counter is 0 again. So what will happen? Until 40 the pulse will be on and the rest 60 pulses will be off. So, we can get a 40% duty cycle at a frequency 1Hz. Now to increase this frequency simply increase timer interrupt speed i.e. reduce time.
C++:
/*******************************************************************************
Program for, PWM generation using PIC12F675
Program Written by_ Engr. Mithun K. Das; mithun060@gmail.com
MCU
Date: 30-03-2021; © labprojectsbd.com
*******************************************************************************/
#define pwm_pin GP0_bit
unsigned int scale=0,duty=0;
void InitTimer0()
{
OPTION_REG = 0x80;
TMR0 = 200;
INTCON = 0xA0;
}
void Timer_interrupt() iv 0x0004 ics ICS_AUTO
{
if (TMR0IF_bit)
{
TMR0IF_bit = 0;
TMR0 = 200; // change this value [0-255] to change the total frequency.
scale++;
if(scale<duty)
{
pwm_pin = 1;
}
else
{
pwm_pin = 0;
}
if(scale>100)scale=0;
}
}
void main()
{
TRISIO = 0b00000000;//set I/O
GPIO = 0x00;
CMCON = 0x07;//comparator off
ANSEL = 0b00000000;
InitTimer0();
while(1)
{
duty = 90;
}//end of while(1)
}//end of void main
//End
Circuit diagram:
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