toggle LED on Raspberry Pi GPIO on/off given MCP3304 ADC to OPT101 ambient light reading

nightlight.py

#!/usr/bin/python
# nightlight.py - toggle LED on Raspberry Pi GPIO on/off given MCP3304 ADC to OPT101 ambient light reading
# https://medium.com/@rxseger/spi-interfacing-experiments-eeproms-bus-pirate-adc-opt101-with-raspberry-pi-9c819511efea

import spidev
import time
import RPi.GPIO as GPIO

# /dev/spidev(bus).(dev)
SPI_BUS = 0
# CE0 = 0, CE1=1
SPI_DEV = 0
# MCP3304 channel number, 0 to 7
ADC_CHANNEL = 7

# voltages if greater than or less than, recognize as light or dark (in between, no change)
V_LIGHT = 0.7  # turn off when light out
V_DARK = 0.6   # turn on when it is dark

# GPIO port for nightlight
LED_Y = 32 # G12


GPIO.setmode(GPIO.BOARD)
GPIO.setwarnings(False)
GPIO.setup([LED_Y], GPIO.OUT, initial=GPIO.HIGH)

spi = spidev.SpiDev()
spi.open(SPI_BUS, SPI_DEV)

# based on http://www.havnemark.dk/?p=54 and http://jeremyblythe.blogspot.ca/2012/09/raspberry-pi-hardware-spi-analog-inp
def readadc(adcnum):
	# read SPI data from MCP3008 chip, 8 possible adc's (0 thru 7)
	if adcnum > 7 or adcnum < 0:
		return -1

	# Frame format: 0000 1SCC | C000 000 | 000 000
	r = spi.xfer2([((adcnum & 6) >> 1)+12 , (adcnum & 1) << 7, 0])
	adcout = ((r[1] & 15) << 8) + r[2]

	# Read from ADC channels and convert the bits read into the voltage
	# Divisor changed from 1023 to 4095, due to 4 more bits
	return (adcout * 3.3) / 4095

def set_light(on):
	GPIO.output(LED_Y, not on) # active-low

while True:
	v = readadc(7)
	#print v
	if v > V_LIGHT:
		set_light(False)
	elif v < V_DARK:
		set_light(True)
	time.sleep(0.1)