they're just ST microcontrollers. you can put your own firmware on and do what you like with the hardware. The hardware consists of an incandescent bulb and

they're just ST microcontrollers. you can put your own firmware on and do what you like with the hardware. The hardware consists of an incandescent bulb and photodiode with amplifier and high res ADC. The bulb and photodiode sit in a box with a silvered interior, which allows light from the bulb to reflect around inside the box a lot (and having some light absorbed by CO2) before hitting the photodiode.