//something like this
import RPi.GPIO as GPIO
import time

channel = 17
GPIO.setmode(GPIO.BCM)
GPIO.setup(channel, GPIO.IN)
count = 0

def callback(channel):
    if GPIO.input(channel):
        print " PWM high value"
        count += 1
    else:
        print " PWM Low value"

GPIO.add_event_detect(channel, GPIO.BOTH, bouncetime=300)
#assign callback function to GPIO pin
GPIO.add_event_callback(channel, callback)

while True:
    time.sleep(1)