Adafruit SCD4X CO2 sensor for ESP32

An Arduino sketch for the Adafruit SCD4X CO2 sensor and Adafruit SCD-30 CO2 sensor running on an ESP32 with an http server returning Prometheus compatible responses.

Related software:

Setup

WiFi:

Copy the secrets file: cp secrets.tmpl.h secrets.h
Fill in your SSID and password in secrets.h
Note: my ESP32 Thing would only connect to a 2.4 GHz network

Arduino:

Download the latest version of Arduino from https://www.arduino.cc
From Tools > Manage Libraries... add the library: Sensirion I2C SCD4x
If you have an SCD-30 CO2 sensor, add the library: Adafruit SCD30
Install the Sensirion BLE library: cd ~/Documents/Arduino/library and then git clone https://github.com/Sensirion/arduino-ble-gadget.git
Install the NimBLE library: cd ~/Documents/Arduino/library and then git clone https://github.com/h2zero/NimBLE-Arduino.git
Connect your ESP32 via USB
From Tools > Board choose your ESP32 board, port, and speed: 115200
Now try Upload to send the code to your ESP32

Note: If you have an SCD-30 CO2 sensor, make sure you're on the branch add/2-scd-30 before uploading the sketch: git checkout add/2-scd-30

iOS/macOS Bluetooth app:

I built an iOS/macOS app so location data can be saved with CO2 reading data.

Project code: ios-ble-co2-sensor

This code also works with the standard Sensirion MyAmbience app:

Install the Sensirion MyAmbience app: iOS/Android
Turn on Bluetooth on your device
The readings should update every 5 seconds

Serial monitor

If you open the Arduino serial monitor you'll see:

The WiFi output as it attempts to connect to your WiFi network
The http response including the SCD4X/SCD-30 CO2 readings

http response

Once your ESP32 has connected to your SSID, it will respond over port 80 with a Prometheus response. e.g. curl 192.168.1.100:80/metrics

# HELP ambient_temperature Ambient temperature
# TYPE ambient_temperature gauge
ambient_temperature 29.70
# HELP ambient_humidity Ambient humidity
# TYPE ambient_humidity gauge
ambient_humidity 55.85
# HELP co2 CO2
# TYPE co2 gauge
co2 627

My ESP32 Thing with the SCD-41 CO2 sensor running off of two recycled 18650 laptop batteries.

Thanks

Shoutout to Core Electronics for being so fast with their delivery of the Adafruit SCD-41.

Licenses

My code: MIT License
ESP32 example code SimpleWiFiServer by Jan Hendrik Berlin
Sensirion I2C SCD4X example code exampleUsage license:

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
Neither the name of Sensirion AG nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

emanuelduss / co2_sensor_scd4x_esp32_http_server