CO2-mini

README.md

$ sudo apt-get install \
    python3-dev \
    librrd-dev \
    libudev-dev \
    libusb-1.0-0-dev
$ python3 -m pip install wheel
$ python3 -m pip install hidapi rrdtool

$ mkdir data
$ rrdtool \
  create ./data/temperature.rrd \
  --step 10 \
  --start now-1h \
  DS:celsius:GAUGE:600:U:U \
  RRA:AVERAGE:0.5:1m:8d \
  RRA:AVERAGE:0.5:5m:90d \
  RRA:MIN:0.5:1h:366d \
  RRA:MAX:0.5:1h:366d \
  RRA:AVERAGE:0.5:1h:366d 
$ rrdtool \
  create ./data/co2.rrd \
  --step 10 \
  --start now-1h \
  DS:ppm:GAUGE:600:U:U \
  RRA:AVERAGE:0.5:1m:8d \
  RRA:AVERAGE:0.5:5m:90d \
  RRA:MIN:0.5:1h:366d \
  RRA:MAX:0.5:1h:366d \
  RRA:AVERAGE:0.5:1h:366d

co2mini.py

# -*- coding: utf-8 -*-

# https://github.com/heinemml/CO2Meter/blob/master/CO2Meter.py

from datetime import datetime

import hid
import rrdtool

key = [0xc4, 0xc6, 0xc0, 0x92, 0x40, 0x23, 0xdc, 0x96]
RRD_TEMP = 'data/temperature.rrd'
RRD_CO2 = 'data/co2.rrd'


def main():
    co2_last_time = 0
    temp_last_time = 0

    device = hid.device()
    device.open(0x04d9, 0xa052)
    try:
        device.send_feature_report(bytearray([0] + key))

        while True:
            data = device.read(8)
            if len(data) != 8:
                print('unexpected length')
                continue
            if data[4] != 0x0d or (sum(data[:3]) & 0xff) != data[3]:
                print('checksum')
                continue

            value = data[1] << 8 | data[2]
            now = int(datetime.now().timestamp())
            if data[0] == 0x50:
                if (now - co2_last_time) < 1:
                    continue
                rrdtool.update(RRD_CO2, f'{now:d}:{value:d}')
                co2_last_time = now
            elif data[0] == 0x42:
                if (now - temp_last_time) < 1:
                    continue
                value = value / 16.0 - 273.1
                rrdtool.update(RRD_TEMP, f'{now:d}:{value:.1f}')
                temp_last_time = now
            else:
                # print('unknown', data[0])
                pass

    finally:
        device.close()


if __name__ == '__main__':
    main()