import RPi.GPIO as GPIO
import time
from smbus import SMBus
bus = SMBus(1)
an0 = 0
led3 = 25

color_pw = 20

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.setup(led3,GPIO.OUT)
GPIO.setup(color_pw,GPIO.OUT)

GPIO.output(led3,GPIO.LOW)
GPIO.output(color_pw,GPIO.HIGH)

def read_ain(i):    
    global bus
    bus.write_byte(0x48, i)
    bus.read_byte(0x48)
    return bus.read_byte(0x48)
print "CTRL+C = STOP program"

try:
    while True:
        an0 = read_ain(1)
        val = 160 - an0 # PULL UP on 3.3V
        ledv = val + 70 # > 150 turn LED ON  (50%)       
        print str(an0)
        print "-"
        bus.write_byte_data(0x48, 0x40, ledv) # analog LED     
        if an0 < 150:
            GPIO.output(led3,GPIO.HIGH)
            br3 = 0
        else:
            GPIO.output(led3,GPIO.LOW)
            
except KeyboardInterrupt:
    GPIO.cleanup()  # must be executed before program stop