65 lines
2.5 KiB
Markdown
65 lines
2.5 KiB
Markdown
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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 on 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 = 0x44
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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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