local_air_quality_node.py

"""
This script regularly takes air quality measurements from the Alphasense OPC-N3
and 5 different Alphasense electrochemical B4 gas sensors. The data is stored 
locally in a CSV file and published to AWS IoT via MQTT.
"""

####################### IMPORTS ########################

import spidev
import opc
import time
import datetime
import csv
import logging
import json
import Adafruit_DHT
from ADCPi import ADCPi
from gpiozero import LED



##################### SENSOR SETUP #####################

# Setup SPI
spi = spidev.SpiDev()
spi.open(0, 0)
spi.mode = 1
spi.max_speed_hz = 500000

# Setup OPC-N3
opcn3 = opc.OPCN3(spi)

# Setup ADCs for gas sensors
adc1 = ADCPi(0x68, 0x69, 16) 	# Channels: SO2 (1-2), NO2 (3-4), NO2+O3 (5-6),
adc2 = ADCPi(0x6A, 0x6B, 16)	# Channels: CO (1-2) , NO (3-4)

# Setup DHT22 temp/humidity sensor
dht22 = Adafruit_DHT.DHT22
dht_pin = 4

# Setup LED
led = LED(17)


################## GLOBAL VARIABLES ####################

# Node information
node_id = 1

# Sampling period
sampling_period = 2.0 # 5-10s total, AWS connection time uncertain

# AWS IoT variables

client_id = "RPi-AQ-Node" + str(node_id)


##################### FUNCTIONS ########################

def get_data():

	# Open CSV file
	with open("/home/pi/outdoor-node/data/node" + str(node_id) + "_" + now + ".csv", 'a') as f:
		writer = csv.DictWriter(f, fieldnames=fnames)
		csv_row = {}

		# Take measurement from each sensor
		timestamp = datetime.datetime.utcnow().isoformat()
		csv_row['timestamp'] = timestamp
		csv_row['node_id'] = client_id

		print "****************************************"
		print "Timestamp: ", timestamp
		print "Node ID: ", client_id
		print ""

		humidity, temp = Adafruit_DHT.read_retry(dht22, dht_pin)
		csv_row['temperature'] = round(float(temp),2)
		csv_row['humidity'] = round(float(humidity),2)

		print "Temperature: {0}{1}C".format(round(temp,1), u'\u00b0'.encode('utf8'))
		print "Humidity: {0}%".format(round(humidity,1))
		print ""

		so2_w_raw = adc1.read_voltage(1) * 1000.0
		so2_a_raw = adc1.read_voltage(2) * 1000.0
		csv_row['so2_we'] = round(so2_w_raw,3)
		csv_row['so2_ae'] = round(so2_a_raw,3)

		no2_w_raw = adc1.read_voltage(3) * 1000.0
		no2_a_raw = adc1.read_voltage(4) * 1000.0
		csv_row['no2_we'] = round(no2_w_raw,3)
		csv_row['no2_ae'] = round(no2_a_raw,3)

		ox_w_raw = adc1.read_voltage(5) * 1000.0
		ox_a_raw = adc1.read_voltage(6) * 1000.0
		csv_row['ox_we'] = round(ox_w_raw,3)
		csv_row['ox_ae'] = round(ox_a_raw,3)

		co_w_raw = adc2.read_voltage(1) * 1000.0
		co_a_raw = adc2.read_voltage(2) * 1000.0
		csv_row['co_we'] = round(co_w_raw,3)
		csv_row['co_ae'] = round(co_a_raw,3)

		no_w_raw = adc2.read_voltage(3) * 1000.0
		no_a_raw = adc2.read_voltage(4) * 1000.0
		csv_row['no_we'] = round(no_w_raw,3)
		csv_row['no_ae'] = round(no_a_raw,3)

		print "EC Sensor Raw Voltages:"
		print "SO2:    WE = {0}mV, AE = {1}mV".format(round(so2_w_raw,3), round(so2_a_raw,3))
		print "NO2:    WE = {0}mV, AE = {1}mV".format(round(no2_w_raw,3), round(no2_a_raw,3))
		print "NO2+O3: WE = {0}mV, AE = {1}mV".format(round(ox_w_raw,3), round(ox_a_raw,3))
		print "CO:     WE = {0}mV, AE = {1}mV".format(round(co_w_raw,3), round(co_a_raw,3))
		print "NO:     WE = {0}mV, AE = {1}mV".format(round(no_w_raw,3), round(no_a_raw,3))
		print ""

		print "PM Measurements:"
		pm_data = opcn3.histogram()
		pm2_5 = pm_data['PM_B']
		pm10 = pm_data['PM_C']
		csv_row['pm2_5'] = round(pm2_5,3)
		csv_row['pm10'] = round(pm10,3)

		print "PM  2.5: {0}{1}g/m{2}".format(round(pm2_5,2), u'\u00B5'.encode('utf8'), u'\u00B3'.encode('utf8'))
		print "PM 10.0: {0}{1}g/m{2}".format(round(pm10,2), u'\u00B5'.encode('utf8'), u'\u00B3'.encode('utf8'))
		print "****************************************"
		print ""

		# Flash LED while sending data
		led.on()
		time.sleep(0.1)

		# Write row to local CSV file
		writer.writerow(csv_row)


# Configure logging
def configureLogging():
    logger = logging.getLogger(__file__)
    logger.setLevel(logging.DEBUG)
    streamHandler = logging.StreamHandler()
    formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
    streamHandler.setFormatter(formatter)
    logger.addHandler(streamHandler)



######################### RUN ###########################

print "***STARTING SENSORS***"

# Turn on OPC sensor
opcn3.on()
led.on()
time.sleep(10)

# Read and discard the first histogram as per Alphasense guidance
data = {}
data = opcn3.histogram()

# Create local output CSV file
now = datetime.datetime.now().strftime("%d%m%Y-%H%M")
f = open("/home/pi/outdoor-node/data/node" + str(node_id) + "_" + now + ".csv", 'w+')
fnames = ['timestamp', 'node_id', 'temperature', 'humidity', 'pm2_5', 'pm10', 'so2_we', 'so2_ae', 'no2_we', 'no2_ae', 'ox_we', 'ox_ae', 'co_we', 'co_ae', 'no_we', 'no_ae']
writer = csv.DictWriter(f, fieldnames=fnames)
writer.writeheader()
f.close()

# Let sensors stabilise for 10 minutes as per Alphasense guidance
print ""
print "Waiting for sensors to stabilise..."
time.sleep(600)

print ""
print "***SENSORS STARTED, PRESS CTRL+C TO STOP***"
print ""

# Loop for taking measurements from sensors, stop with CTRL+C
proceed = True
while proceed == True:
	try:
		# Take measurements from sensors
		datapoints = get_data()

		# Flash LED each time data is sent
		led.off()

		# Wait for next sample
		time.sleep(sampling_period)

	except KeyboardInterrupt:
		proceed = False
		print ""
		print "***INTERUPT DETECTED***"
		print "***SHUTTING DOWN***"

		opcn3.off()

# Turn the opc OFF
opcn3.off()