Sensirion Raspberry Pi I2C SEN5x Driver

This document explains how to set up the Sen5x sensor to run on a Raspberry Pi using the provided code.

Supported sensors

• SEN50 (only particulate matter signals available)
• SEN54 (no NOx signal available)
• SEN55 (full feature set)

Setup Guide

Connecting the Sensor

Your sensor has the five different connectors: VCC, GND, SDA, SCL, SEL (the sixth connector will not be used for now). Use the following pins to connect your SEN5x:

SEN5x	Raspberry Pi	Jumper Wire
VCC	Pin 2 (5V)	Red
GND	Pin 6	Black
SDA	Pin 3	Green
SCL	Pin 5	Yellow
SEL	Pin 9 (GND for I2C)	Blue

Pin	Name	Description	Comments
1	VCC	Supply Voltage	5V ±10%
2	GND	Ground
3	SDA	I2C: Serial data input / output	TTL 5V and LVTTL 3.3V compatible
4	SCL	I2C: Serial clock input	TTL 5V and LVTTL 3.3V compatible
5	SEL	Interface select	Pull to GND to select I2C
6	NC	Do not connect

Raspberry Pi

• Install the Raspberry Pi OS on to your Raspberry Pi
• Enable the I2C interface in the raspi-config
• Download the driver for the Sensirion Github Page and extract the .zip on your Raspberry Pi
• Compile the driver

  1. Open a terminal

  2. Navigate to the driver directory. E.g. cd ~/raspberry-pi-i2c-sen5x

  3. Run the make command to compile the driver

     Output:

     rm -f sen5x_i2c_example_usage
     cc -Os -Wall -fstrict-aliasing -Wstrict-aliasing=1 -Wsign-conversion -fPIC -I. -o sen5x_i2c_example_usage  sen5x_i2c.h sen5x_i2c.c sensirion_i2c_hal.h sensirion_i2c.h sensirion_i2c.c \
         sensirion_i2c_hal.c sensirion_config.h sensirion_common.h sensirion_common.c sen5x_i2c_example_usage.c
     

• Test your connected sensor

  • Run ./sen5x_i2c_example_usage in the same directory you used to compile the driver.

    Output:

    Serial number: 213100019
    Product name: 
    Firmware: 1.0, Hardware: 4.0
    Mass concentration pm1p0: 0.0 µg/m³
    Mass concentration pm2p5: 0.0 µg/m³
    Mass concentration pm4p0: 0.0 µg/m³
    Mass concentration pm10p0: 0.0 µg/m³
    Ambient humidity: 39.6 %RH
    Ambient temperature: 28.0 °C
    Voc index: 0.0
    Nox index: 0.0
    Mass concentration pm1p0: 0.0 µg/m³
    Mass concentration pm2p5: 0.0 µg/m³
    Mass concentration pm4p0: 0.0 µg/m³
    Mass concentration pm10p0: 0.0 µg/m³
    Ambient humidity: 39.2 %RH
    Ambient temperature: 30.1 °C
    Voc index: 0.0
    Nox index: 0.0
    ...
    

  • Wait a few minutes until Voc/NOx index values are stable.

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

• Ensure that you connected the sensor correctly: All cables are fully plugged in and connected to the correct pin.
• Ensure that I2C is enabled on the Raspberry Pi. For this redo the steps on "Enable the I2C interface in the raspi-config" in the guide above.
• Ensure that your user account has read and write access to the I2C device. If it only works with user root (sudo ./sen5x_i2c_example_usage), it's typically due to wrong permission settings. See the next chapter how to solve this.

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 ${USER} i2c
Adding user `pi' to group `i2c' ...
Adding user pi 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 reasonably 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