Module to get CO2 readings from a co2mini device (sold under various names), with USB ID 04d9:a052
In FHEM do this:
update add https://raw.githubusercontent.com/ThorstenPferdekaemper/FHEM-co2mini/master/controls_co2mini.txt
update all co2mini
Wait for it to finish, including commandref rebuild.
shutdown restart
The CO2 sensor appears as /dev/hidraw, e.g. /dev/hidraw0. Make sure that the fhem user can access this device file. The easiest way to achieve this is by copying the file /opt/fhem/FHEM/lib/co2mini/90-co2mini.rules into directory /etc/udev/rules.d and then reboot the system. This makes sure that the device is accessible by the fhem user under the name /dev/co2mini0. This probably does not work if you have multiple co2mini sensors attached.
Check local commandref for co2mini on how to create the co2mini device in FHEM.
Reverse engineering documented in https://hackaday.io/project/5301-reverse-engineering-a-low-cost-usb-co-monitor