“Read SHT31” Command-Line Tool

For various sensors, attached to Raspberry-Pi computers, I wrote small command-line tools to read the sensor values over the I2C connection. While you can do this with a Python script directly, I found using a compiled C or C++ program accessing the low-level device more reliable.

The program I publish today, reads temperature and humidity data from a SHT31 sensor. It outputs a simple JSON document you can parse in your script.

Usage

There are a number of arguments you can use:

Usage: read_sht31 [-h][-v]
 -h|--help   Display this help.
 -s          Get the sensor status.
 -t1 -t0     Enable/disable heater.
 -a0 -a1     Select the chip address. 0 is the default.
 -b0 -b1     Select the bus. 1 is the default.
 -d          Show debugging messages.

If you call the command, you will get JSON output:

$ read_sht32
{ "temperature_celsius": 24.8, "relative_humidity": 28.4 }

The idea is to call this command from your script and parse the returned JSON output.

Compile and Install

In order to compile and install the tool on your Raspberry-Pi, you need to install the compiler, CMake and the I2C-Tools first:

sudo apt install gcc cmake i2c-tools

Download the files of this git repository to a subdirectory in your home directory. In this example, I downloaded the files to the directory /home/pi/read_sht31.

Now create a separate build directory. In this example, I create the directory /home/pi/build_read_sht31.

Next switch to the build directory, execute cmake to create the build script. Build the executable with make and install the executable in your system with sudo make install.

cd build_read_sht31
cmake ../read_sht31
make
sudo make install

Download

Download or clone the files from GitHub:

License

The code is licensed under the GPL license version 3.

Available Sensors

The SHT31 sensor is available from various sources as breakout board. Here two examples:

• Adafruit Breakout
• Breakout from DFRobot

Conclusion

Hopefully this small tool will help with your next Raspberry-Pi project. 😄

If you have any questions, missed information, or simply want to provide feedback, feel free to comment below or contact me on Twitter. 😄

More Posts

“Read SGP30” Command-Line Tool

I published another small command-line tool for Raspberry-Pi. This time one to read data from the Sensirion SGP30 sensor. While you can communicate over I2C with sensors using Python, I found it not as reliable ...
Read More

Circle Pattern Generator

I wrote a small application to generate random circle patterns. You just specify the width and height of the rectangle to fill and the application will fill the area with the circles you specified. The ...
Read More

Regular Storage Boxes Update

The regular storage boxes set got an update today. All existing boxes are now available in a new revision with an improved corner design and there are four new boxes in the set. The title ...
Read More

Let’s Print a Cat/Pet Feeding Device (Part 1)

Do you own a 3D printer and would like to start a complex and challenging project? Then let's print a fully functional, programmable cat or pet feeding device! 😄 In this multi-part series, I will ...
Read More

Let’s Print a Cat/Pet Feeding Device (Part 2)

In this part, we assemble the gearbox. It is the second part of this series. If you missed the first one, read it here. Requirements for this Part You will need the printed objects from ...
Read More

Tall Boxes Ready for Download

The tall boxes set is ready for download, after successfully completing my tests. You will get carefully designed storage boxes, optimised for 3d print from the ground up. Only this weekend, from 2020-11-27 to 2020-11-29, ...
Read More