--->>> 예제  pwm_led02.c    PWM Ports C (Software PWM)  <<<------------
#include <wiringPi.h> /* include wiringPi library */
#include <stdio.h> 
#include <softPwm.h>  /* include header file for software PWM */

int main(){
int PWM_pin = 1; /* GPIO1 as per WiringPi,GPIO18 as per BCM */
int intensity;
wiringPiSetup(); /* initialize wiringPi setup */
pinMode(PWM_pin,OUTPUT); /* set GPIO as output */
softPwmCreate(PWM_pin,1,100); /* set PWM channel along with range*/
while (1)
  {
for (intensity = 0; intensity < 101; intensity++)
{
  softPwmWrite (PWM_pin, intensity); /* change the value of PWM */
  delay (10) ;
}
delay(1);

for (intensity = 100; intensity >= 0; intensity--)
{
  softPwmWrite (PWM_pin, intensity);
  delay (10);
}
delay(1);

}
}
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$ gcc  -o pwm_led02  pwm_led02.c  -lwiringPi
$ sudo  pwm_led02
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