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Read an SDS011 Laser PM2.5 Sensor (Nova PM Sensor) with Python
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#!/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" |
Now added upload to thingspeak.
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I changed the byte order, as the first byte is the low byte, and the second the high byte.
I've also set the parameters as args for the serial.Serial instanciation.