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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

Open a terminal
Navigate to the driver directory. E.g. cd ~/raspberry-pi-i2c-sen44

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.