Introduction

CircuitPython library for the Adafruit SGP40 Air Quality Sensor / VOC Index Sensor Breakouts

Dependencies

This driver depends on:

• Adafruit CircuitPython
• Bus Device
• Register

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle.

Installing from PyPI

On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI. To install for current user:

pip3 install adafruit-circuitpython-sgp40

To install system-wide (this may be required in some cases):

sudo pip3 install adafruit-circuitpython-sgp40

To install in a virtual environment in your current project:

mkdir project-name && cd project-name
python3 -m venv .venv
source .venv/bin/activate
pip3 install adafruit-circuitpython-sgp40

Usage Example

import time
import board
import adafruit_sgp40

i2c = board.I2C()  # uses board.SCL and board.SDA
sgp = adafruit_sgp40.SGP40(i2c)

while True:
    print("Measurement: ", sgp.raw)
    print("")
    sleep(1)

For humidity compensated raw gas and voc index readings, we'll need a secondary sensor such as the bme280

import time
import board
import adafruit_sgp40
import adafruit_bme280

i2c = board.I2C()  # uses board.SCL and board.SDA
sgp = adafruit_sgp40.SGP40(i2c)
bme280 = adafruit_bme280.Adafruit_BME280_I2C(i2c)

while True:
    temperature = bme280.temperature
    humidity = bme280.relative_humidity

    # For compensated raw gas readings
    """
    compensated_raw_gas = sgp.measure_raw(
        temperature=temperature, relative_humidity=humidity
    )
    print("Raw Data:", compensated_raw_gas)
    """

    # For Compensated voc index readings
    voc_index = sgp.measure_index(
    temperature=temperature, relative_humidity=humidity)

    print("VOC Index:", voc_index)
    print("")
    time.sleep(1)

It may take several minutes for the VOC index to start changing as it calibrates the baseline readings. The voc algorithm expects a 1 hertz sampling rate. Run measure_index() once per second.

Documentation

API documentation for this library can be found on Read the Docs.

For information on building library documentation, please check out this guide.

Contributing

Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.