standalonePMS.py

import serial
import time
import datetime
import csv
from pprint import pprint  # makes data more pretty

# add a config file which is unique to each sniffy.
monitorID = 2 # Imput a sensor number here 

# setup onboard serial port NB RPi 3 address
port = serial.Serial('/dev/ttyS0', baudrate=9600, timeout=2.0)
broker = "mqtt.opensensors.io"  # "46.101.13.195"     # test broker
topic = "/orgs/solentairwatch/sniffy"
monitorLocation = [50.9262, -1.4092]
csvFile = "stJohn2.csv" # keep a local copy for debug

def on_connect(client, userdata, rc):
    print("Connected with result code " + str(rc))
    # do nothing we're connected
    pass


def on_publish(client, userdata, mid):
    print(mid)
    # print('published a message')
    pass


def on_disconnect(client, userdata, rc):
    # need some ability to error log and reconnect
    print('disconected with code' + str(rc))
    

# function to read a line of serial data
def read_pm_line(_port):
    rv = b''
    while True:
        ch1 = _port.read()
        if ch1 == b'\x42':
            ch2 = _port.read()
            if ch2 == b'\x4d':
                rv += ch1 + ch2
                rv += _port.read(28)
                return rv

# set up objects
f = open(csvFile,'a')
message = {
	'time': str(datetime.datetime.now()),
	'id': monitorID,
	'cityName': "Southampton",
	'stationName': "StJohn1",
	'averaging': 0,
        'latitude': monitorLocation[0],
        'longitude': monitorLocation[1],
	'PM1': 0,
	'PM25': 0,
	'PM10': 0,
	'PM10_STD': 0,
	'PM25_STD': 0,
	'PM100_STD': 0,
	'gr03um': 0,
	'gt05um': 0,
	'gr10um': 0,
	'gr25um': 0,
	'gr50um': 0,
	'gr100um': 0}
w = csv.DictWriter(f, message.keys())
w.writeheader()


while True: # PMSx003 sensor by default streams data and non-uniform intervals - replace with timed polling
    try:
        #print("trying to read")
        rcv = read_pm_line(port)
        # print("is reading")
        #  The following needs updating to work on python 3
        message = {
            'time': str(datetime.datetime.now()),
            'id': monitorID,
            'cityName': "Southampton",
            'stationName': "Common#1",
            'latitude': monitorLocation[0],
            'longitude': monitorLocation[1],
            'averaging': 0,
            'PM1': ord(rcv[4]) * 256 + ord(rcv[5]),
            'PM25': ord(rcv[6]) * 256 + ord(rcv[7]),
            'PM10': ord(rcv[8]) * 256 + ord(rcv[9]),
            'PM10_STD': ord(rcv[10]) * 256 + ord(rcv[11]),
            'PM25_STD': ord(rcv[12]) * 256 + ord(rcv[13]),
            'PM100_STD': ord(rcv[14]) * 256 + ord(rcv[15]),
            'gr03um': ord(rcv[16]) * 256 + ord(rcv[17]),
            'gt05um': ord(rcv[18]) * 256 + ord(rcv[19]),
            'gr10um': ord(rcv[20]) * 256 + ord(rcv[21]),
            'gr25um': ord(rcv[22]) * 256 + ord(rcv[23]),
            'gr50um': ord(rcv[24]) * 256 + ord(rcv[25]),
            'gr100um': ord(rcv[26]) * 256 + ord(rcv[27])
            }
        # pprint(message)
        w.writerow(message)
        
        time.sleep(0.1) # wait 100 millisonds

    except KeyboardInterrupt:
        break