Sensirion I²C STC3X Arduino Library

This is the Sensirion STC3X library for Arduino allowing you to communicate with a sensor of the STC3X family over I²C.

Click here to learn more about the Sensirion STC3X sensor family.

The measured gas mixture depends on the STC3x product and configured binary gas. Please refer to the datasheet and API documentation to get a list of supported binary gases.

Supported sensor types

Sensor name	I²C Addresses
STC31-C	0x29
STC31	0x29

The following instructions and examples use a STC31-C.

Installation of the library

This library can be installed using the Arduino Library manager: Start the Arduino IDE and open the Library Manager via

Sketch ➔ Include Library ➔ Manage Libraries...

Search for the Sensirion I2C STC3X library in the Filter your search... field and install it by clicking the install button.

If you cannot find it in the library manager, download the latest release as .zip file and add it to your Arduino IDE via

Sketch ➔ Include Library ➔ Add .ZIP Library...

Don't forget to install the dependencies listed below the same way via library manager or Add .ZIP Library

Dependencies

• Sensirion Core

Sensor wiring

Use the following pin description to connect your STC3X to the standard I²C bus of your Arduino board:

Pin	Cable Color	Name	Description	Comments
1	red	VDD	Supply Voltage	2.7V to 5.5V
2	yellow	SCL	I2C: Serial clock input
3	black	GND	Ground
4	green	SDA	I2C: Serial data input / output

The recommended voltage is 3.3V.

Board specific wiring

You will find pinout schematics for recommended board models below:

Arduino Uno

STC3X	STC3X Pin	Cable Color	Board Pin
VDD	1	red	3.3V
SCL	2	yellow	D19/SCL
GND	3	black	GND
SDA	4	green	D18/SDA

Arduino Nano

STC3X	STC3X Pin	Cable Color	Board Pin
VDD	1	red	3.3V
SCL	2	yellow	A5
GND	3	black	GND
SDA	4	green	A4

Arduino Micro

STC3X	STC3X Pin	Cable Color	Board Pin
VDD	1	red	3.3V
SCL	2	yellow	~D3/SCL
GND	3	black	GND
SDA	4	green	D2/SDA

Arduino Mega 2560

STC3X	STC3X Pin	Cable Color	Board Pin
VDD	1	red	3.3V
SCL	2	yellow	D21/SCL
GND	3	black	GND
SDA	4	green	D20/SDA

ESP32 DevKitC

STC3X	STC3X Pin	Cable Color	Board Pin
VDD	1	red	3V3
SCL	2	yellow	GPIO 22
GND	3	black	GND
SDA	4	green	GPIO 21

Quick Start

1. Install the libraries and dependencies according to Installation of the library

2. Connect the STC3X sensor to your Arduino as explained in Sensor wiring

3. Open the exampleUsage sample project within the Arduino IDE:

   File ➔ Examples ➔ Sensirion I2C STC3X ➔ exampleUsage

   The provided example is working with a STC31-C, I²C address 0x29. In order to use the code with another product or I²C address you need to change it in the code of examples/exampleUsage. You find the list with pre-defined addresses in src/SensirionI2CSTC3X.h.

4. Click the Upload button in the Arduino IDE or Sketch ➔ Upload

5. When the upload process has finished, open the Serial Monitor or Serial Plotter via the Tools menu to observe the measurement values. Note that the Baud Rate in the used tool has to be set to 115200 baud.

Additional Examples

Forced Recalibration

There is a detailed explenation, see Documentation.

To run the example, open the exampleUsageFrc sample project within the Arduino IDE.

Example for mesaurement with RHT Compenstation

To run the example, open the measurementWithCompenstation sample project within the Arduino IDE.

Contributing

Contributions are welcome!

We develop and test this driver using our company internal tools (version control, continuous integration, code review etc.) and automatically synchronize the master branch with GitHub. But this doesn't mean that we don't respond to issues or don't accept pull requests on GitHub. In fact, you're very welcome to open issues or create pull requests :)

This Sensirion library uses clang-format to standardize the formatting of all our .cpp and .h files. Make sure your contributions are formatted accordingly:

The -i flag will apply the format changes to the files listed.

clang-format -i src/*.cpp src/*.h

Note that differences from this formatting will result in a failed build until they are fixed. :

License

See LICENSE.