It's easy to use the SCD-30 with Python or CircuitPython, and the Adafruit CircuitPython SCD30 module. This module allows you to easily write Python code that reads CO2, temperature, and humidity from the SCD30 sensor.

You can use this sensor with any CircuitPython microcontroller board or with a computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library.

CircuitPython Microcontroller Wiring

First wire up a SCD-30 to your board exactly as shown below. Here's an example of wiring a Feather M4 to the sensor with I2C using one of the handy STEMMA QT connectors:

  • Board 3V to sensor VIN (red wire)
  • Board GND to sensor GND (black wire)
  • Board SCL to sensor SCL (yellow wire)
  • Board SDA to sensor SDA (blue wire)

You can also use the standard 0.100" pitch headers to wire it up on a breadboard:

  • Board 3V to sensor VIN (red wire)
  • Board GND to sensor GND (black wire)
  • Board SCL to sensor SCL (yellow wire)
  • Board SDA to sensor SDA (blue wire)

Python Computer Wiring

Since there's dozens of Linux computers/boards you can use, we will show wiring for Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to see whether your platform is supported

Here's the Raspberry Pi wired to the sensor using I2C and a STEMMA QT connector:

  • Pi 3V to sensor VIN (red wire)
  • Pi GND to sensor GND (black wire)
  • Pi SCL to sensor SCL (yellow wire)
  • Pi SDA to sensor SDA (blue wire)

Finally here is an example of how to wire up a Raspberry Pi to the sensor using a solderless breadboard

  • Pi 3V to sensor VIN (red wire)
  • Pi GND to sensor GND (black wire)
  • Pi SCL to sensor SCL (yellow wire)
  • Pi SDA to sensor SDA (blue wire)

CircuitPython Installation of SCD30 Library

You'll need to install the Adafruit CircuitPython SCD30 library on your CircuitPython board.

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle.  Our CircuitPython starter guide has a great page on how to install the library bundle.

Required libraries:

  • adafruit_scd30.mpy
  • adafruit_bus_device/
  • adafruit_register/

Your CIRCUITPY drive should look like the image.

Before continuing make sure your board's lib folder or root filesystem has the adafruit_scd30.mpy file, and the adafruit_bus_device and adafruit_register folders copied over.

Python Installation of SCD30 Library

You'll need to install the Adafruit_Blinka library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready!

Once that's done, from your command line run the following command:

  • sudo pip3 install adafruit-circuitpython-scd30

If your default Python is version 3 you may need to run 'pip' instead. Just make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.

CircuitPython & Python Usage

To demonstrate the usage of the sensor we'll initialize it and read the CO2, temperature and humidity data from the board's Python REPL.

Run the following code to import the necessary modules and initialize the I2C connection with the sensor:

import board
import adafruit_scd30

scd = adafruit_scd30.SCD30(board.I2C())

Now you're ready to read values from the sensor using these properties:

  • data_available - Check the sensor to see if new data is available.
  • eCO2 - The CO2 concentration in PPM (parts per million).
  • temperature - The current temperature in degrees Celsius.
  • relative_humidity - The current relative humidity in %rH.
print("Data available?", scd.data_available)
print("CO2:", scd.CO2, "PPM")
print("Temperature:", scd.temperature, "degrees C")
print("Humidity:", scd.relative_humidity, "%%rH")

Full Example Code

# SPDX-FileCopyrightText: 2020 by Bryan Siepert, written for Adafruit Industries
#
# SPDX-License-Identifier: Unlicense
import time
import board
import busio
import adafruit_scd30

# SCD-30 has tempremental I2C with clock stretching, datasheet recommends
# starting at 50KHz
i2c = busio.I2C(board.SCL, board.SDA, frequency=50000)
scd = adafruit_scd30.SCD30(i2c)

while True:
    # since the measurement interval is long (2+ seconds) we check for new data before reading
    # the values, to ensure current readings.
    if scd.data_available:
        print("Data Available!")
        print("CO2: %d PPM" % scd.CO2)
        print("Temperature: %0.2f degrees C" % scd.temperature)
        print("Humidity: %0.2f %% rH" % scd.relative_humidity)
        print("")
        print("Waiting for new data...")
        print("")

    time.sleep(0.5)

You'll be able to get a new reading every 2 seconds, that's as fast as data comes out of the sensor.

It's normal for the first reading to be 0, as the sensor 'warms up'. Simply skip that reading when logging data.

To change things like the interval delay (how often data is calculated)  check out this example which shows how you can tweak the sensor to change the interval, or tune the sensor with things like the known altitude/barometric pressure. Check the datasheet for the SCD-30 for more details on tuning the sensor.

# SPDX-FileCopyrightText: 2020 by Bryan Siepert, written for Adafruit Industries
#
# SPDX-License-Identifier: Unlicense
import time
import board
import busio
import adafruit_scd30

# SCD-30 has tempremental I2C with clock stretching, datasheet recommends
# starting at 50KHz
i2c = busio.I2C(board.SCL, board.SDA, frequency=50000)
scd = adafruit_scd30.SCD30(i2c)
# scd.temperature_offset = 10
print("Temperature offset:", scd.temperature_offset)

# scd.measurement_interval = 4
print("Measurement interval:", scd.measurement_interval)

# scd.self_calibration_enabled = True
print("Self-calibration enabled:", scd.self_calibration_enabled)

# scd.ambient_pressure = 1100
print("Ambient Pressure:", scd.ambient_pressure)

# scd.altitude = 100
print("Altitude:", scd.altitude, "meters above sea level")

# scd.forced_recalibration_reference = 409
print("Forced recalibration reference:", scd.forced_recalibration_reference)
print("")

while True:
    data = scd.data_available
    if data:
        print("Data Available!")
        print("CO2:", scd.CO2, "PPM")
        print("Temperature:", scd.temperature, "degrees C")
        print("Humidity::", scd.relative_humidity, "%%rH")
        print("")
        print("Waiting for new data...")
        print("")

    time.sleep(0.5)

This guide was first published on Jan 06, 2021. It was last updated on 2021-02-21 13:57:29 -0500.

This page (Python & CircuitPython) was last updated on Oct 23, 2021.

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