ky006.py

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
 
#The output pin
GPIO_PIN = 21
GPIO.setup(GPIO_PIN, GPIO.OUT)

pwm = GPIO.PWM(GPIO_PIN, 500)
pwm.start(50)
# The program will wait for the input of a new frequency.

try:
    while(True):
        print "----------------------------------------"
        print "Current frequency: %d" % 500
        Frequency = input("Please input a new frequency (50-5000):")
        pwm.ChangeFrequency(Frequency)
         
except KeyboardInterrupt:
    GPIO.cleanup()