🎉 Initial commit

.flake8

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+[flake8]
+ignore = E203, E266, E501, W503
+max-line-length = 80
+max-complexity = 18
+select = B,C,E,F,W,T4,B9
+# We need to configure the mypy.ini because the flake8-mypy's default
+# options don't properly override it, so if we don't specify it we get
+# half of the config from mypy.ini and half from flake8-mypy.
+mypy_config = mypy.ini

.gitignore

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+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+pip-wheel-metadata/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+.python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+data

.isort.cfg

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+[settings]
+multi_line_output=3
+include_trailing_comma=True
+force_grid_wrap=0
+use_parentheses=True
+line_length=88

.pre-commit-config.yaml

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+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.4.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-yaml
+    -   id: check-added-large-files
+-   repo: https://github.com/psf/black
+    rev: 19.10b0
+    hooks:
+    -   id: black
+-   repo: https://github.com/pre-commit/mirrors-isort
+    rev: v4.3.21
+    hooks:
+    -   id: isort

90-co2mini.rules

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+ACTION=="remove", GOTO="co2mini_end"
+
+SUBSYSTEMS=="usb", KERNEL=="hidraw*", ATTRS{idVendor}=="04d9", ATTRS{idProduct}=="a052", GROUP="plugdev", MODE="0660", SYMLINK+="co2mini%n", GOTO="co2mini_end"
+
+LABEL="co2mini_end"

README.md

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+# CO2 monitoring with Prometheus
+
+This reads from the CO2 Meter and makes it available as a Prometheus service.
+The core logic comes from [this hackaday article](https://hackaday.io/project/5301-reverse-engineering-a-low-cost-usb-co-monitor/log/17909-all-your-base-are-belong-to-us).
+
+## Setup
+
+1. Install Python 3
+2. Install python3-prometheus-client
+3. Set up CO2 udev rules by copying `90-co2mini.rules` to `/etc/udev/rules.d/90-co2mini.rules`
+4. Set up the service by copying `co2_prometheus.service` to `/lib/systemd/system/co2_prometheus.service`
+5. Run `systemctl enable co2_prometheus.service`

co2_prometheus.service

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+[Unit]
+Description=CO2 Monitoring via Prometheus
+After=multi-user.target
+
+[Service]
+Type=idle
+ExecStart=/usr/bin/python3 /home/pi/co2_prometheus/main.py /dev/co2mini0
+
+[Install]
+WantedBy=multi-user.target

co2_prometheus/main.py

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+#!/usr/bin/env python3
+
+import fcntl
+import logging
+import os
+import sys
+
+from prometheus_client import Counter, Gauge, start_http_server
+
+co2_gauge = Gauge("co2", "CO2 levels in PPM")
+temp_gauge = Gauge("temperature", "Temperature in C")
+checksum_error_counter = Counter("checksum_errors", "Number of checksum errors seen")
+
+logger = logging.getLogger(__name__)
+PROMETHEUS_PORT = os.getenv("CO2_PROMETHEUS_PORT", 9999)
+
+# From http://co2meters.com/Documentation/AppNotes/AN146-RAD-0401-serial-communication.pdf
+OP_CO2 = 0x50
+OP_TEMP = 0x42
+
+
+def decrypt(key, data):
+    # Magic from https://hackaday.io/project/5301-reverse-engineering-a-low-cost-usb-co-monitor/log/17909-all-your-base-are-belong-to-us
+    cstate = [0x48, 0x74, 0x65, 0x6D, 0x70, 0x39, 0x39, 0x65]
+    shuffle = [2, 4, 0, 7, 1, 6, 5, 3]
+
+    phase1 = [0] * 8
+    for i, o in enumerate(shuffle):
+        phase1[o] = data[i]
+
+    phase2 = [0] * 8
+    for i in range(8):
+        phase2[i] = phase1[i] ^ key[i]
+
+    phase3 = [0] * 8
+    for i in range(8):
+        phase3[i] = ((phase2[i] >> 3) | (phase2[(i - 1 + 8) % 8] << 5)) & 0xFF
+
+    ctmp = [0] * 8
+    for i in range(8):
+        ctmp[i] = ((cstate[i] >> 4) | (cstate[i] << 4)) & 0xFF
+
+    out = [0] * 8
+    for i in range(8):
+        out[i] = (0x100 + phase3[i] - ctmp[i]) & 0xFF
+
+    return out
+
+
+def hd(d):
+    return " ".join("%02X" % e for e in d)
+
+
+if __name__ == "__main__":
+    # Key retrieved from /dev/random, guaranteed to be random ;)
+    key = [0xC4, 0xC6, 0xC0, 0x92, 0x40, 0x23, 0xDC, 0x96]
+
+    fp = open(sys.argv[1], "a+b", 0)
+
+    HIDIOCSFEATURE_9 = 0xC0094806
+    set_report = [0] + key
+    fcntl.ioctl(fp, HIDIOCSFEATURE_9, bytearray(set_report))
+
+    values = {}
+
+    # Expose metrics
+    start_http_server(PROMETHEUS_PORT)
+
+    while True:
+        data = list(fp.read(8))
+        decrypted = decrypt(key, data)
+        if decrypted[4] != 0x0D or (sum(decrypted[:3]) & 0xFF) != decrypted[3]:
+            logger.warning("Checksum error: %s => %s", hd(data), hd(decrypted))
+            checksum_error_counter.inc()
+        else:
+            op = decrypted[0]
+            val = decrypted[1] << 8 | decrypted[2]
+
+            if op == OP_CO2:
+                co2_gauge.set(val)
+            if op == OP_TEMP:
+                temp_gauge.set(val / 16.0 - 273.15)

requirements.txt

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+prometheus_client