import RPi.GPIO as GPIO      
import time
GPIO.setmode(GPIO.BOARD)
GPIO.setup(16, GPIO.OUT) 
#FRRRRRekvence 
p = GPIO.PWM(16,30)      
p.start(0) 
try:
 while True:
  for i in range (100):
   p.ChangeDutyCycle(i)
   time.sleep(0.02)        
  for i in range(100):
   p.ChangeDutyCycle(100-i)
   time.sleep(0.01)       
except KeyboardInterrupt:
 pass                   
p.stop()
GPIO.cleanup()