PCF8574OneShot.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

import os
import time
import datetime
import MySQLdb as mdb
import logging
import smbus
from heatingToAWS import sendHeatingData
#### Import dB Details from access.py
from access import hostname, username, password, dB

# PCF8574 commands
PCF8574		= 0x20

logging.basicConfig(filename='/home/pi/log/PCF8574_error.log',
  level=logging.DEBUG,
  format='%(asctime)s %(levelname)s %(name)s %(message)s')
logger=logging.getLogger(__name__)

# General read function, also updates a register

def write(address, value):
	try:
		bus.write_byte(address,value)
	except IOError as io_err:
		logger.error(io_err)
		print(io_err)
	return -1

def read(address):
	try:
		reading = bus.read_byte(address)
	except IOError as io_err:
		logger.error(io_err)
		print(io_err)
	return reading

################################################
#
#      Start of "Main"
#
################################################ 

# Set up variables

# Get readings from sensors and store them in MySQL

bus = smbus.SMBus(1)

write(PCF8574, 0xFF)

try:
	pins = read(PCF8574)
	print ("%02x" % pins)
#	print pins
#		As the most significant two bits are unconnected,
#		they should always be high. Hence, if the value of 
#		the pins is less than 192 (C0) we need to reset.
	if (pins < 0xC0):
		print ("Resetting to FF")
		write(PCF8574, 0xFF)
	else:
		sendHeatingData(pins)
except IOError as io_error:
	print("bus Read error", io_error)
	print( "Clash")