Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
135 lines (111 sloc) 4.48 KB
#!/usr/bin/env python
########################################################################
# Calibration and read of the CO2 sensor MH-Z16
# according to the datasheet : http://www.seeedstudio.com/wiki/images/c/ca/MH-Z16_CO2_datasheet_EN.pdf
# output value directly in ppm
# Doms made
# History
# ------------------------------------------------
# Author Date Comments
# Doms 13 04 15 Initial Authoring
#
'''
## License
The MIT License (MIT)
GrovePi for the Raspberry Pi: an open source platform for connecting Grove Sensors to the Raspberry Pi.
Copyright (C) 2017 Dexter Industries
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
'''
#
########################################################################
import os
import serial, time
import smbus
import math
import RPi.GPIO as GPIO
import struct
import sys
import datetime
import grovepi
import struct
from grovepi import *
#
__author__ = 'Doms Genoud'
#co2 sensor
#use an external usb to serial adapter
ser = serial.Serial('/dev/ttyUSB0', 9600, timeout = 1) #Open the serial port at 9600 baud
#To open the raspberry serial port
#ser = serial.Serial('/dev/ttyAMA0', 9600, timeout = 1) #Open the serial port at 9600 baud
#init serial
ser.flush()
############# carbon dioxid CO2 #####################
class CO2:
#inspired from c code of http://www.seeedstudio.com/wiki/Grove_-_CO2_Sensor
#Gas concentration= high level *256+low level
inp =[]
cmd_zero_sensor = "\xff\x87\x87\x00\x00\x00\x00\x00\xf2"
cmd_span_sensor = "\xff\x87\x87\x00\x00\x00\x00\x00\xf2"
cmd_get_sensor = "\xff\x01\x86\x00\x00\x00\x00\x00\x79"
def read(self):
try:
while True:
ser.write(CO2.cmd_get_sensor)
CO2.inp = ser.read(9)
high_level = struct.unpack('B',CO2.inp[2])[0]
low_level = struct.unpack('B',CO2.inp[3])[0]
temp_co2 = struct.unpack('B',CO2.inp[4])[0] - 40
#output in ppm
conc = high_level*256+low_level
return [conc,temp_co2]
except IOError:
return [-1,-1]
def calibrateZero(self):
try:
ser.write(CO2.cmd_zero_sensor)
print("CO2 sensor zero calibrated")
except IOError:
print("CO2 sensor calibration error")
def calibrateSpan(self):
try:
while True:
#ser.write(CO2.cmd_zero_sensor)
print("CO2 sensor span calibrated")
break
except IOError:
print("CO2 sensor calibration error")
########################################################################################################
############# MAIN
########################################################################################################
# following the specs of the sensor :
# read the sensor, wait 3 minutes, set the zero, read the sensor
c = CO2()
while True:
try:
#CO2 sensor calib
print("wait 3 minutes to warm up CO2 sensor")
time.sleep(180)
print("Read before calibration-->",c.read())
print("calibrating...")
co2 = c.calibrateZero()
time.sleep(5)
print("Read after calibration-->",c.read())
print("DONE")
break
except IndexError:
print("Unable to read")
except KeyboardInterrupt:
print("Exiting")
sys.exit(0)
You can’t perform that action at this time.