p267 6-5 콜백방식

#btn_callback.py
import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)
count = 0
def handler(channel):
    global count
    count = count +1
    print count

GPIO.setup(24, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
GPIO.add_event_detect(24,GPIO.RISING, callback=handler)
while True:
    time.sleep(1)

리눅스 커널자체에 GPIO driver가 들어가 있는데 그것 도움을 받아서