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