Sensirion Raspberry Pi I2C SFA3x Driver

This document explains how to set up the SEK-SFA3x sensor module to run on a Raspberry Pi using the provided code.

Setup Guide

Connecting the Sensor

Your sensor has seven different connectors: VCC, GND, SDA, SCL, SEL (the sixth and seventh connector will not be used for now). Use the following pins to connect your SFA3x:

SFA3x	Raspberry Pi	Jumper Wire
VCC	Pin 1 or 2 (3.3V or 5V)	Red
GND	Pin 6	Black
SDA	Pin 3	Green
SCL	Pin 5	Yellow
SEL	Pin 9 (GND for I2C)	Blue

If you don't have a suitable cable at hand, please find the SEK-SFA3x pinout listed below, or in the datasheet:

Pin	Name	Description	Comments
1	VDD	Supply Voltage	5V ±10%
2	GND	Ground
3	RX	UART: Receiving pin for communication
	SDA	I2C: Serial data input / output
4	TX	UART: Transmission pin for communication
	SCL	I2C: Serial clock input
5	SEL	Interface select	Leave floating or pull to VDD to select UART
			Pull to GND to select I2C
6	NC	Do not connect
7	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-sfa3x

  3. Run the make command to compile the driver

     Output:

     rm -f sfa3x_i2c_example_usage
     cc -Os -Wall -fstrict-aliasing -Wstrict-aliasing=1 -Wsign-conversion -fPIC -I. -o sfa3x_i2c_example_usage  sfa3x_i2c.h sfa3x_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 sfa3x_i2c_example_usage.c
     

• Test your connected sensor

  • Run ./sfa3x_i2c_example_usage in the same directory you used to compile the driver.

    Output:

    Device marking: 494108010320N020234S
    Formaldehyde concentration: 0.0 ppb
    Relative humidity: 35.35 %RH
    Temperature: 25.28 °C
    Formaldehyde concentration: 0.0 ppb
    Relative humidity: 35.34 %RH
    Temperature: 25.26 °C
    Formaldehyde concentration: 0.0 ppb
    Relative humidity: 35.36 %RH
    Temperature: 25.28 °C
    Formaldehyde concentration: 0.0 ppb
    Relative humidity: 35.34 %RH
    Temperature: 25.28 °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 ./sfa3x_i2c_example_usage), it's typically due to wrong permission settings.