Read value
import RPi.GPIO as GPIO
# read value
GPIO.setmode(GPIO.BCM)
GPIO.setup(21, GPIO.IN)
poweron = GPIO.input(21)
GPIO.cleanup(21)
print "turnonheater"
GPIO.setup(21,GPIO.OUT, initial=GPIO.HIGH)
GPIO.output(21, GPIO.HIGH)
GPIO.cleanup(21)
print "turnoffheater"
GPIO.setup(21,GPIO.OUT, initial=GPIO.LOW)
GPIO.output(21, GPIO.LOW)
GPIO.cleanup(21)
