Sensirion Raspberry Pi I2C SEN44 Driver

This document explains how to set up the SEN44 sensor module to run on a Raspberry Pi using the provided code.

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 SEN44:

SEN44	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	VDD	Supply Voltage	5V ±10%
2	GND	Ground
3	RX	UART: Receiving pin for communication	TTL 5V and LVTTL 3.3V compatible
	SDA	I2C: Serial data input / output	TTL 5V and LVTTL 3.3V compatible
4	TX	UART: Transmission pin for communication	TTL 5V and LVTTL 3.3V compatible
	SCL	I2C: Serial clock input	TTL 5V and LVTTL 3.3V compatible
5	SEL	Interface select	Leave floating or pull to VDD to select UART
			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-sen44

  3. Run the make command to compile the driver

     Output:

     rm -f sen44_i2c_example_usage
     cc -Os -Wall -fstrict-aliasing -Wstrict-aliasing=1 -Wsign-conversion -fPIC -I. -o sen44_i2c_example_usage  sen44_i2c.h sen44_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 sen44_i2c_example_usage.c
     

• Test your connected sensor

  • Run ./sen44_i2c_example_usage in the same directory you used to compile the driver.

    Output:

    Serial number: C081C2651224B6FE
    Firmware: 0.4, Hardware: 6.0
    Mass concentration pm1p0: 1 µg/m³
    Mass concentration pm2p5: 5 µg/m³
    Mass concentration pm4p0: 9 µg/m³
    Mass concentration pm10p0: 11 µg/m³
    Voc index: 0.0
    Ambient humidity: 36.77 %RH
    Ambient temperature: 26.20 °C
    Mass concentration pm1p0: 4 µg/m³
    Mass concentration pm2p5: 6 µg/m³
    Mass concentration pm4p0: 7 µg/m³
    Mass concentration pm10p0: 8 µg/m³
    Voc index: 0.0
    Ambient humidity: 36.77 %RH 
    Ambient temperature: 26.20 °C
    ...
    

Troubleshooting

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 ./sen44_i2c_example_usage), it's typically due to wrong permission settings.