STCC4 CO₂, Temperature and Relative Humidity Sensor

The stcc4 sensor platform allows you to use your Sensirion STCC4 CO₂ (datasheet) sensor with ESPHome. The I²C Bus is required to be set up in your configuration for this sensor to work.

The STCC4 is a miniature CO₂ sensor based on thermal conductivity measurement. It features a dedicated I²C controller interface for connecting a Sensirion SHT4x temperature and humidity sensor, which provides both onboard temperature/humidity readings and signal compensation for accurate CO₂ measurements.

# Example configuration with onboard SHT4x
sensor:
  - platform: stcc4
    co2:
      name: "CO2 Concentration"
    temperature:
      name: "Temperature"
    humidity:
      name: "Humidity"

NOTE

The STCC4 evaluation kit (SEK-STCC4) includes an SHT4x sensor connected to the STCC4’s dedicated I²C controller interface. The STCC4 reads the SHT4x automatically and returns temperature and humidity alongside CO₂ in each measurement. These values are exposed as optional sensor outputs.

Configuration variables

co2 (Optional): The CO₂ concentration sensor in ppm.
- All options from Sensor.
temperature (Optional): The temperature sensor from the onboard SHT4x (°C).
- All options from Sensor.
humidity (Optional): The relative humidity sensor from the onboard SHT4x (%).
- All options from Sensor.
temperature_source (Optional, ID): The ID of an external temperature sensor for RHT compensation. Only needed for boards without an onboard SHT4x connected to the STCC4’s dedicated I²C bus. Must be used together with humidity_source.
humidity_source (Optional, ID): The ID of an external humidity sensor for RHT compensation. Only needed for boards without an onboard SHT4x connected to the STCC4’s dedicated I²C bus. Must be used together with temperature_source.
ambient_pressure_compensation (Optional, int): Enable compensation of measured CO₂ values based on given ambient pressure in hPa.
ambient_pressure_compensation_source (Optional, ID): The ID of a pressure sensor for dynamic pressure compensation. The sensor must report pressure in hPa/mBar.
measurement_mode (Optional): Set measurement mode for the STCC4.
- continuous: The sensor takes measurements continuously at 1-second intervals (default).
- single_shot: A measurement is started at each update interval. A measurement takes approximately 500ms.
address (Optional, int): Manually specify the I²C address of the sensor. Defaults to 0x64.
update_interval (Optional, Time): The interval to check the sensor. Defaults to 60s.

Temperature and Humidity Compensation

The STCC4 uses thermal conductivity to measure CO₂ concentration. This measurement principle is affected by temperature and humidity, so compensation is required for accurate readings.

Boards with onboard SHT4x (recommended)

The STCC4 evaluation kit and most breakout boards include an SHT4x sensor connected to the STCC4’s dedicated I²C controller. In this configuration, compensation is handled automatically and you can read temperature and humidity directly:

sensor:
  - platform: stcc4
    co2:
      name: "CO2"
    temperature:
      name: "Temperature"
    humidity:
      name: "Humidity"

Boards without onboard SHT4x

If your board does not have an SHT4x connected to the STCC4’s dedicated I²C bus, you can provide external temperature and humidity values using the temperature_source and humidity_source options. These values are sent to the sensor via the set_rht_compensation command:

sensor:
  - platform: sht4x
    temperature:
      id: temp_sensor
    humidity:
      id: humidity_sensor

  - platform: stcc4
    co2:
      name: "CO2"
    temperature_source: temp_sensor
    humidity_source: humidity_sensor

Pressure Compensation

Ambient pressure affects CO₂ readings. You can set a static pressure value or use a dynamic pressure sensor:

Static pressure compensation

sensor:
  - platform: stcc4
    co2:
      name: "CO2"
    ambient_pressure_compensation: 1013

Dynamic pressure compensation

sensor:
  - platform: bme280_i2c
    pressure:
      name: "Pressure"
      id: pressure_sensor

  - platform: stcc4
    co2:
      name: "CO2"
    ambient_pressure_compensation_source: pressure_sensor

Specifications

CO₂ measurement range: 400 - 5000 ppm (accurate), up to 32000 ppm (supported)
Accuracy: ±(100 ppm + 10% of reading) at 400-5000 ppm with SHT4x compensation
I²C address: 0x64 (default), 0x65 (alternative)
Measurement technology: Thermal conductivity