CO2MiniMon
This Linux program reads temperature and relative CO2 concentration data from a CO2Mini sensor and writes the values to temporary files. I use it to display the data in i3status.
Setup
Put the udev rules file in /etc/udev/rules.d/, then reload the rules with:
# udevadm control --reload-rules && udevadm trigger
Then, when you plug in the device, /dev/co2minix will be created as a symlink
to the appropriate /dev/hidrawx.
Build and run:
$ ./build.sh
$ ./out/release/co2minimon
The 2 output files specified in the source code should be created and continually updated with the latest values.
Device Support
There are different versions of this device, frequently called the CO2Mini or the RAD-0301.
Some versions use a crappy encryption scheme as a detterent to getting the data out. For some wonderful and informative reading on this subject, see Reverse-Engineering a low-cost USB CO₂ monitor.
For whatever reason, my device doesn't seem to engage in these encryption shenanigans, so I can just get the data by decoding the very simple protocol.
My device has model number ZGm053UKA, and Linux reports the following data
for it:
# lsusb --verbose -d 04d9:a052
Bus 001 Device 020: ID 04d9:a052 Holtek Semiconductor, Inc. USB-zyTemp
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.10
bDeviceClass 0
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x04d9 Holtek Semiconductor, Inc.
idProduct 0xa052 USB-zyTemp
bcdDevice 2.00
iManufacturer 1 Holtek
iProduct 2 USB-zyTemp
iSerial 3 2.00
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 0x0022
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
(Bus Powered)
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 3 Human Interface Device
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
HID Device Descriptor:
bLength 9
bDescriptorType 33
bcdHID 1.10
bCountryCode 0 Not supported
bNumDescriptors 1
bDescriptorType 34 Report
wDescriptorLength 53
Report Descriptors:
** UNAVAILABLE **
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0008 1x 8 bytes
bInterval 10
Device Status: 0x0000
(Bus Powered)