#!/usr/bin/env python

## Process to read serial output from ES642 Dust Monitor
## Data is stored in daily files within the data directory
## Original code base written by Joe Young (University of Utah) for ceilometer use
## Slightly modified for air quality sensor use by Alex Jacques (University of Utah - April 2018)
## Code contact email: alexander.jacques@utah.edu

## Import Modules

import serial, time, os, sys, datetime, subprocess

## Configurations for serial and output files

configs = {
	"CODEDIR":"/home/pi/es642/code/",
	"DATADIR":"/home/pi/es642/data/",
	"BAUDRATE":9600,
	"BYTESIZE":8,
	"PORT":0,
	"FILENAME":"ES642",
	"DATEFMT":"%Y%m%d",
	"DELAY":0.5
}

## Check if process had been previously running, don't restart if it is running!

statuscheck = subprocess.check_output("ps -ef | grep es642_data_read",shell=True).splitlines()
stringcheck = 'python /home/pi/es642/code/es642_data_read.py'
totalproc = 0

for eachproc in statuscheck:
	if(eachproc.find(stringcheck) == -1):
		skip = 1
	else:
		print "Found process: "+eachproc+"\n"
		totalproc = totalproc + 1

print "Total processes: "+str(totalproc)

if(totalproc > 1):
	print "Exiting"
	sys.exit()

## The dust monitor should be connected to the Pi using a USB-RS232 cable
## Loop through serial USB port listings and attempt to open port connection to USB-RS232 cable

ser = serial.Serial()
ser.baudrate = configs["BAUDRATE"]
ser.bytesize = configs["BYTESIZE"]
port = configs["PORT"]
while port < 20:
	try:
		ser.port = '/dev/ttyUSB%i' % port
		print ser.port
		if not os.path.exists(ser.port):
			port += 1
			continue
		ser.open()
		break  # try no more!
	except serial.serialutil.SerialException as e:
		print e
		port += 1
if port == 20:
	print 'No valid USB serial port identified so exiting'
	sys.exit()

print "Connected to a USB device on {}".format(ser.port)

## Now keep the USB port connection constantly open
## When a new serial message is received from the dust monitor, output the current UTC timestamp and the data message into the data file

ob = ''
while 1:
	ln = ser.readline()
	time.sleep(configs["DELAY"])
	if not ln:
		continue
	if(len(ln) > 7):	
		fileoutname = ("%s%s_%s.dat" % (configs["DATADIR"],configs["FILENAME"],datetime.datetime.utcnow().strftime(configs["DATEFMT"])))
		fouthandle = open(fileoutname,'a')
		fouthandle.write(str(datetime.datetime.utcnow().strftime('%Y-%m-%d,%H:%M:%S,'))+str(ln))
		fouthandle.close()

sys.exit()