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Sensirion Raspberry Pi I2C SCD4x Driver

This document explains how to set up the SCD4x sensor to run on a Raspberry Pi using the provided code.

<center><img src="images/SCD41_Development_Board.png" width="300px"></center>

Click here to learn more about the SCD4x sensor and the SCD41 Evaluation Kit Board.

Setup Guide

Connecting the Sensor

Your sensor has the four different connectors: VCC, GND, SDA, SCL. Use the following pins to connect your SCD4x:

SCD4xRaspberry PiJumper Wire
VCCPin 1Red
GNDPin 6Black
SDAPin 3Green
SCLPin 5Yellow
<center><img src="images/GPIO-Pinout-Diagram.png" width="900px"></center>

Raspberry Pi

Troubleshooting

Building driver failed

If the execution of make in the compilation step 3 fails with something like

-bash: make: command not found

your RaspberryPi likely does not have the build tools installed. Proceed as follows:

$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get install build-essential

Initialization failed

If you run ./scd4x_i2c_example_usage but do not get sensor readings but something like this instead

Error executing scd4x_get_serial_number(): -1
Error executing scd4x_start_periodic_measurement(): -1
Error executing scd4x_read_measurement(): -1

then go through the below troubleshooting steps.

Missing I2C permissions

If your user is missing access to the I2C interface you should first verfiy the user belongs to the i2c group.

$ groups
users input some other groups etc

If i2c is missing in the list add the user and restart the Raspberry Pi.

$ sudo adduser your-user i2c
Adding user `your-user' to group `i2c' ...
Adding user your-user to group i2c
Done.
$ sudo reboot

If that did not help you can make globally accessible hardware interfaces with a udev rule. Only do this if everything else failed and you are reasoably confident you are the only one having access to your Pi.

Go into the /etc/udev/rules.d folder and add a new file named local.rules.

$ cd /etc/udev/rules.d/
$ sudo touch local.rules

Then add a single line ACTION=="add", KERNEL=="i2c-[0-1]*", MODE="0666" to the file with your favorite editor.

$ sudo vi local.rules