I have solved it by introducing a pwm converter connected to esp32. Esp32 reads data from Netatmo inhouse air quality monitor towers. Values are then converted to voltage by help of mentioned pwm converter and feeds that value into dedicated input on C6 board for CO2. Theres a defined range from 0 to 10V that you can feed into C6 controllers CO2 . Asked also if CO2 values can be sent via modbus. Komfovent technicians said it is not possible