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179
CO2Meter.py
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179
CO2Meter.py
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"""
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Module for reading out CO2Meter USB devices
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via a hidraw device under Linux
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"""
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import sys
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import fcntl
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import threading
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import weakref
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CO2METER_CO2 = 0x50
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CO2METER_TEMP = 0x42
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CO2METER_HUM = 0x41
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HIDIOCSFEATURE_9 = 0xC0094806
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def _co2_worker(weak_self):
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"""
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Worker thread that constantly reads from the usb device.
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"""
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while True:
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self = weak_self()
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if self is None:
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break
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self._read_data()
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if not self._running:
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break
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del self
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class CO2Meter:
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_key = [0xc4, 0xc6, 0xc0, 0x92, 0x40, 0x23, 0xdc, 0x96]
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_device = ""
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_values = {}
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_file = ""
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_running = True
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_callback = None
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def __init__(self, device="/dev/hidraw0", callback=None):
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self._device = device
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self._callback = callback
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self._file = open(device, "a+b", 0)
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if sys.version_info >= (3,):
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set_report = [0] + self._key
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fcntl.ioctl(self._file, HIDIOCSFEATURE_9, bytearray(set_report))
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else:
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set_report_str = "\x00" + "".join(chr(e) for e in self._key)
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fcntl.ioctl(self._file, HIDIOCSFEATURE_9, set_report_str)
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thread = threading.Thread(target=_co2_worker, args=(weakref.ref(self),))
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thread.daemon = True
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thread.start()
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def _read_data(self):
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"""
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Function that reads from the device, decodes it, validates the checksum
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and adds the data to the dict _values.
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Additionally calls the _callback if set
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"""
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try:
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result = self._file.read(8)
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if sys.version_info >= (3,):
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data = list(result)
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else:
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data = list(ord(e) for e in result)
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if data[4] != 0x0d:
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""" newer devices don't encrypt the data, if byte 4!=0x0d assume encrypted data """
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data = self._decrypt(data)
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if data[4] != 0x0d or (sum(data[:3]) & 0xff) != data[3]:
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print(self._hd(data), "Checksum error")
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return
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operation = data[0]
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val = data[1] << 8 | data[2]
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self._values[operation] = self._convert_value(operation, val)
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if self._callback is not None:
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if operation in {CO2METER_CO2, CO2METER_TEMP} or (operation == CO2METER_HUM and val != 0):
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self._callback(sensor=operation, value=val)
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except:
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self._running = False
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def _decrypt(self, data):
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"""
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The received data has some weak crypto that needs to be decoded first
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"""
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cstate = [0x48, 0x74, 0x65, 0x6D, 0x70, 0x39, 0x39, 0x65]
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shuffle = [2, 4, 0, 7, 1, 6, 5, 3]
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phase1 = [0] * 8
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for i, j in enumerate(shuffle):
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phase1[j] = data[i]
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phase2 = [0] * 8
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for i in range(8):
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phase2[i] = phase1[i] ^ self._key[i]
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phase3 = [0] * 8
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for i in range(8):
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phase3[i] = ((phase2[i] >> 3) | (phase2[(i - 1 + 8) % 8] << 5)) & 0xff
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ctmp = [0] * 8
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for i in range(8):
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ctmp[i] = ((cstate[i] >> 4) | (cstate[i] << 4)) & 0xff
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out = [0] * 8
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for i in range(8):
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out[i] = (0x100 + phase3[i] - ctmp[i]) & 0xff
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return out
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@staticmethod
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def _convert_value(sensor, value):
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""" Apply Conversion of value dending on sensor type """
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if sensor == CO2METER_TEMP:
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return round(value / 16.0 - 273.1, 1)
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if sensor == CO2METER_HUM:
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return round(value / 100.0, 1)
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return value
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@staticmethod
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def _hd(data):
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""" Helper function for printing the raw data """
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return " ".join("%02X" % e for e in data)
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def get_co2(self):
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"""
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read the co2 value from _values
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:returns dict with value or empty
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"""
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if not self._running:
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raise IOError("worker thread couldn't read data")
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result = {}
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if CO2METER_CO2 in self._values:
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result = {'co2': self._values[CO2METER_CO2]}
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return result
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def get_temperature(self):
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"""
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reads the temperature from _values
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:returns dict with value or empty
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"""
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if not self._running:
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raise IOError("worker thread couldn't read data")
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result = {}
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if CO2METER_TEMP in self._values:
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result = {'temperature': self._values[CO2METER_TEMP]}
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return result
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def get_humidity(self): # not implemented by all devices
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"""
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reads the humidty from _values.
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not all devices support this but might still return a value 0.
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So values of 0 are discarded.
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:returns dict with value or empty
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"""
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if not self._running:
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raise IOError("worker thread couldn't read data")
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result = {}
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if CO2METER_HUM in self._values and self._values[CO2METER_HUM] != 0:
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result = {'humidity': self._values[CO2METER_HUM]}
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return result
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def get_data(self):
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"""
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get all currently available values
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:returns dict with value or empty
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"""
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result = {}
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result.update(self.get_co2())
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result.update(self.get_temperature())
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result.update(self.get_humidity())
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return result
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21
LICENSE
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LICENSE
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MIT License
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Copyright (c) 2017 Michael Heinemann
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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 all
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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 THE
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SOFTWARE.
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64
README.md
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64
README.md
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# CO2Meter
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Python Module to use co2meters like the 'AirCO2ntrol Mini' from TFA Dostmann with USB ID 04d9:a052. There are also other modules using the same interface.
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This module supports Python 2.7 and 3.x.
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## Attribution
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Reverse Engineering of the protocol and initial code done by [Henryk Plötz](https://github.com/henryk).
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Read all about it at [hackaday](https://hackaday.io/project/5301-reverse-engineering-a-low-cost-usb-co-monitor)
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Code derived from [this article](https://hackaday.io/project/5301-reverse-engineering-a-low-cost-usb-co-monitor/log/17909-all-your-base-are-belong-to-us)
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## Install
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With pip:
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```bash
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pip install git+https://github.com/heinemml/CO2Meter
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```
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Without pip:
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```bash
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python setup.py install
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```
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Remark: you don't need to install, you can also just copy the CO2Meter.py into your project.
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If you don't want to run your script as root make sure you have sufficient rights to access the device file.
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This udev rule can be used to set permissions.
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```
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ACTION=="remove", GOTO="co2mini_end"
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SUBSYSTEMS=="usb", KERNEL=="hidraw*", ATTRS{idVendor}=="04d9", ATTRS{idProduct}=="a052", GROUP="plugdev", MODE="0660", SYMLINK+="co2mini%n", GOTO="co2mini_end"
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LABEL="co2mini_end"
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```
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save it as `/etc/udev/rules.d/90-co2mini.rules` and add the script user to the group `plugdev`.
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This rules make the device also available as co2mini0 (increase trailing number for each additional device).
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## Usage
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```python
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from CO2Meter import *
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import time
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sensor = CO2Meter("/dev/hidraw0")
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while True:
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time.sleep(2)
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sensor.get_data()
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```
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The device writes out one value at a time. So we need to parse some data until we have co2 and temperature. Thus the get_data() method will initially return none or only one value (whichever comes first).
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When you just need one measurement you should wait some seconds or iterate until you get a full reading. If you just need co2 a call to `get_co2` might speed things up.
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### Callback
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You can pass a callback to the constructor. It will be called when any of the values is updated. The parameters passed are `sensor` and `value`. `sensor` contains one of these constants:
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```python
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CO2METER_CO2 = 0x50
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CO2METER_TEMP = 0x42
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CO2METER_HUM = 0x41
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```
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### Error handling
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In Case the device can't be read anymore (e.g. it was unplugged) the worker thread will end in the background. Afterwards calls to any of the `get_*` functions will throw an `IOError`. You will need to handle any resetup, making sure that the device is there etc yourself.
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12
example.py
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12
example.py
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#!/bin/env python
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import time
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from datetime import datetime
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from CO2Meter import *
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Meter = CO2Meter("/dev/hidraw0")
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while True:
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measurement = Meter.get_data()
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measurement.update({'timestamp': datetime.now()})
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print(measurement)
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time.sleep(5)
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