Read an SDS011 Laser PM2.5 Sensor (Nova PM Sensor) with Python

sds011.py

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

import serial, time, struct
import httplib, urllib

ser = serial.Serial("/dev/ttyUSB0", baudrate=9600, stopbits=1, parity="N", timeout=2)

ser.flushInput()

KEY = 'your_thingspeak_write_key_here'

byte, lastbyte = "\x00", "\x00"

while True:
    lastbyte = byte
    byte = ser.read(size=1)
    
    # We got a valid packet header
    if lastbyte == "\xAA" and byte == "\xC0":
        sentence = ser.read(size=8) # Read 8 more bytes
        readings = struct.unpack('<hhxxcc',sentence) # Decode the packet - big endian, 2 shorts for pm2.5 and pm10, 2 reserved bytes, checksum, message tail
        
        pm_25 = readings[0]/10.0
        pm_10 = readings[1]/10.0
        # ignoring the checksum and message tail
        #pm_25 = (ord(sentence[0]) | ord(sentence[1])<<8) / 10.0
        #pm_10 = (ord(sentence[2]) | ord(sentence[3])<<8) / 10.0

        params = urllib.urlencode({'field1': pm_25,
                                   'field2': pm_10,
                                   'key':KEY})

        headers = {"Content-type": "application/x-www-form-urlencoded","Accept": "text/plain"}
        conn = httplib.HTTPConnection("api.thingspeak.com:80")                
        try:
            conn.request("POST", "/update", params, headers)
            response = conn.getresponse()
            data = response.read()
            conn.close()
        except Exception, e:
            print "error sending data to thingspeak"

        print "PM 2.5:",pm_25,"μg/m^3  PM 10:",pm_10,"μg/m^3"