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sensor_sds011.py
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sensor_sds011.py
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#!/usr/bin/python -u
# coding=utf-8
# "DATASHEET": http://cl.ly/ekot
# https://gist.github.com/kadamski/92653913a53baf9dd1a8
from __future__ import print_function
import serial, struct, sys, time, json, subprocess, signal, logging
DEBUG = 0
CMD_MODE = 2
CMD_QUERY_DATA = 4
CMD_DEVICE_ID = 5
CMD_SLEEP = 6
CMD_FIRMWARE = 7
CMD_WORKING_PERIOD = 8
MODE_ACTIVE = 0
MODE_QUERY = 1
PERIOD_CONTINUOUS = 0
WAKE_UP_DELAY = 30
SAMPLING_ITI = 15
SENSOR_TIMEOUT = 10
ser = serial.Serial()
ser.port = "/dev/ttyUSB0"
ser.baudrate = 9600
byte, data = 0, ""
def dump(d, prefix=''):
logging.debug(prefix + ' '.join(x.encode('hex') for x in d))
def construct_command(cmd, data=[]):
assert len(data) <= 12
data += [0,]*(12-len(data))
checksum = (sum(data)+cmd-2)%256
ret = "\xaa\xb4" + chr(cmd)
ret += ''.join(chr(x) for x in data)
ret += "\xff\xff" + chr(checksum) + "\xab"
if DEBUG:
dump(ret, '> ')
return ret
def process_data(d):
r = struct.unpack('<HHxxBB', d[2:])
pm25 = r[0]/10.0
pm10 = r[1]/10.0
checksum = sum(ord(v) for v in d[2:8])%256
return [pm25, pm10]
#logging.debug("PM 2.5: {} μg/m^3 PM 10: {} μg/m^3 CRC={}".format(pm25, pm10, "OK" if (checksum==r[2] and r[3]==0xab) else "NOK"))
def process_version(d):
r = struct.unpack('<BBBHBB', d[3:])
checksum = sum(ord(v) for v in d[2:8])%256
logging.debug("Y: {}, M: {}, D: {}, ID: {}, CRC={}".format(r[0], r[1], r[2], hex(r[3]), "OK" if (checksum==r[4] and r[5]==0xab) else "NOK"))
def read_response():
byte = 0
while byte != "\xaa":
byte = ser.read(size=1)
d = ser.read(size=9)
if DEBUG:
dump(d, '< ')
return byte + d
def cmd_set_mode(mode=MODE_QUERY):
ser.write(construct_command(CMD_MODE, [0x1, mode]))
read_response()
def cmd_query_data():
ser.write(construct_command(CMD_QUERY_DATA))
d = read_response()
values = []
if d[1] == "\xc0":
values = process_data(d)
return values
def cmd_set_sleep(sleep):
mode = 0 if sleep else 1
ser.write(construct_command(CMD_SLEEP, [0x1, mode]))
read_response()
def cmd_set_working_period(period):
ser.write(construct_command(CMD_WORKING_PERIOD, [0x1, period]))
read_response()
def cmd_firmware_ver():
ser.write(construct_command(CMD_FIRMWARE))
d = read_response()
process_version(d)
def cmd_set_id(id):
id_h = (id>>8) % 256
id_l = id % 256
ser.write(construct_command(CMD_DEVICE_ID, [0]*10+[id_l, id_h]))
read_response()
def init_sensor():
ser.open()
ser.flushInput()
cmd_set_sleep(0)
cmd_firmware_ver()
cmd_set_working_period(PERIOD_CONTINUOUS)
cmd_set_mode(MODE_QUERY);
signal.signal(signal.SIGALRM, handler)
def get_sensor_data():
cmd_set_sleep(0)
logging.info("Wait a while for the sensor to wake up ...")
time.sleep(WAKE_UP_DELAY)
for t in range(SAMPLING_ITI):
try:
signal.alarm(SENSOR_TIMEOUT)
values = cmd_query_data();
signal.alarm(0)
if values is not None and len(values) == 2:
data = values
logging.debug(str(t) + ". PM2.5: " + str(values[0]) + ", PM10: " + str(values[1]))
time.sleep(2)
except Exception, exc:
logging.error(exc)
# Put sensor to sleep
cmd_set_sleep(1)
time.sleep(10)
return data
def handler(signum, frame):
logging.info("Forever is over!")
raise Exception("end of time")