Sensirion UART SFX6XXX Arduino Library

This is the Sensirion SFX6XXX library for Arduino allowing you to communicate with a sensor of the SFX6XXX family over UART using the SHDLC protocol.

Click here to learn more about the Sensirion SFC6XXX mass flow controller family.

Click here to learn more about the Sensirion SFM6XXX gas flow sensor family.

Supported sensor types

• SFC6000
• SFC6000D-5SLM
• SFC6000D-50SLM
• SFC6000D-20SLM
• SFM6000
• SFM6000D-20SLM
• SFM6000D-50SLM
• SFM6000D-5SLM

The following instructions and examples use a SFC6000.

Installation of the library

This library can be installed using the Arduino Library manager: Start the Arduino IDE and open the Library Manager via

Sketch ➔ Include Library ➔ Manage Libraries...

Search for the Sensririon UART SFX6XXX library in the Filter your search... field and install it by clicking the install button.

If you cannot find it in the library manager, download the latest release as .zip file and add it to your Arduino IDE via

Sketch ➔ Include Library ➔ Add .ZIP Library...

Don't forget to install the dependencies listed below the same way via library manager or Add .ZIP Library

Dependencies

• Sensirion Core

Sensor wiring

Custom sensor connection

For custom setups please check out the detailed sensor pinout.

Detailed sensor pinout

The M8 connector of your SFX6XXX has the following pinout:

Pin	Cable Color	Name	Description	Comments
1	brown	VDD	Supply Voltage	+24V
2	white	D+
3	black	D-
4	blue	GND	Ground

Connecting the Sensor over RS485 converter

To connect the sensor to your Arduino board's serial interface you need a RS485 to TTL converter. For example, you can use the following material:

• RS485 to TTL Converter U094 from M5Stack
• M8 socket to Bare End Cable to connect the sensor to the converter
• Grove to pin header cable to connect the RS485 converter to your Arduino board

Wire the sensor to the RS485 converter using the M8 socket to Bare End Cable:

Sensor Pin	Cable Color	Name	Converter connection	Comments
1	brown	VDD	-	Connect to external power supply (+24V).
2	white	D+	A
3	black	D-	B
4	blue	GND	Ground	Connect the Ground of the external power supply to the adapter ground as well

Wire the RS485 converter to your Arduino board using the Grove to pin header cable:

Converter	Cable Color	Arduino Pin	Comments
TXD	yellow	RX	cross over
RXD	white	TX	cross over
5V	red	5V	Power supply for the RS485 converter
GND	black	GND

Board-specific wiring

We recommend using Arduino Boards or an ESP supporting two or more hardware serial connections to run the example code. One serial port is needed to connect the SFX6XXX sensor and the other one (over USB) for logging to the Serial Monitor of the Arduino IDE.

Arduino Uno, Micro and Nano have only one hardware serial connection and are therefore not recommended to use. There is the option to use the SoftwareSerial library to emulate a serial connection, but it does not work reliably to communicate with the sensor at the required baudrate of 115200 baud. However, you can connect your sensor over the hardware serial connection and use the SoftwareSerial library to set up a connection for logging to the host.

You will find pinout schematics for recommended board models below:

Arduino Mega 2560 Rev3 Pinout

Converter	Cable Color	Arduino Pin	Comments
TXD	yellow	D19 (RX1)	cross over
RXD	white	D18 (TX1)	cross over
5V	red	5V	Power supply for the RS485 converter
GND	black	GND

Note: Make sure to connect serial pins as cross-over (RXD pin of converter -> TX pin on Arduino; TXD pin of converter -> RX pin on Ardunio)

Espressif ESP32-DevKitC Pinout

Converter	Cable Color	ESP Pin	Comments
TXD	yellow	GPIO16 (RXD 2)	cross over
RXD	white	GPIO17 (TXD 2)	cross over
5V	red	5V	Power supply for the RS485 converter
GND	black	GND

Note: Make sure to connect serial pins as cross-over (RXD pin of converter -> TX pin on ESP; TXD pin of converter -> RX pin on ESP)

Quick start example

1. Install the libraries and dependencies according to Installation of the library

2. Connect the SFX6XXX sensor as explained in Sensor wiring

3. Load the exampleUsage sample project within the Arduino IDE:

   File ➔ Examples ➔ Sensirion UART SFX6XXX ➔ exampleUsage

4. Depending on your Arduino board you may need to adapt the code sample. See the board specific instruction section for more information.

5. Make sure to select the correct board model under Tools ➔ Boards and the connected USB port under Tools ➔ Port.

6. Click the Upload button in the Arduino IDE or Sketch ➔ Upload

7. When the upload process has finished, open the Serial Monitor or Serial Plotter via the Tools menu to observe the measurement values. Note that the Baud Rate in the used tool has to be set to 115200 baud.

Board-specific instructions

Arduino Mega 2560

Serial Interface

The provided wiring instructed you to connect the SFX6XXX to Serial Port 1. Therefore, the following line needs to be used in the usage example code:

#define SENSOR_SERIAL_INTERFACE Serial1

Espressif ESP32-DevKitC

ESP32 Library

The ESP32 board is not supported by default with Arduino IDE. If it is your first time using an ESP32 board, you should follow this guide from Esspressif itself.

Serial Interface

The provided wiring instructed you to connect the sensor to Serial Port 2.

Since ESP boards require HardwareSerial implementation, you need to replace the define for the SENSOR_SERIAL_INTERFACE with the following lines in the usage example code:

#include <HardwareSerial.h>
HardwareSerial HwSerial(2);
#define SENSOR_SERIAL_INTERFACE HwSerial

Emulated serial connection for logging (Arduino Uno, Arduino Nano, Arduino Micro)

Use following instructions if your board has only one hardware serial port and you want to emulated a serial connection for logging to the host using the SoftwareSerial library.

• To connect your Arduino to your host for the logging connection, you can for example use the USB to TTL Serial Cable from Adafruit.

  In the example we use Pin 8 and 9 on the Arduino Board for RX/TX.

  Cable wire	Wire color	Arduino Pin
  TX line out of USB	green	Pin8
  RX line into USB	white	Pin9
  ground	black	do not connect
  RX line into USB	red	do not connect

  Note: depending on your Arduino Board not all Pins can be used for RX, see SoftwareSerial documentation for more details.

• Adapt example usage code:

  • Add following header lines and set rxPin and txPin numbers to the pin numbers you connected your serial cable to.

    // Software serial setup
    #include <SoftwareSerial.h>
    #define rxPin 8
    #define txPin 9
    SoftwareSerial sw_serial =  SoftwareSerial(rxPin, txPin);
    

  • Set the define for the serial connection to use to communicate with the sensor to

    For Arduino Uno and Nano:

    #define SENSOR_SERIAL_INTERFACE Serial

    For Arduino Micro:

    #define SENSOR_SERIAL_INTERFACE Serial1

  • In the setup() add following lines of code:

    // Define pin modes for TX and RX
    pinMode(rxPin, INPUT);
    pinMode(txPin, OUTPUT);
    sw_serial.begin(9600);
    

    Remove the initialization lines for Serial used by default for logging.

  • Replace all occurences of Serial.print with sw_serial.print

• Load the example to your Arduino. Make sure to unplug supply voltage (5V pin) of the sensor while doing so, otherwise the Arduino IDE cannot communicate over the serial interface (as the USB Port and the TX/RX Pin use the same HW Serial interface).

• Instead of using the Serial Monitor or Serial Plotter of the Arduino IDE, open a serial monitor on your host system and set the Baudrate to 9600 baud. On Linux you can for example use the grabserial tool:

  grabserial -d /dev/ttyUSB0 -b 9600 --crtonewline

• Press the Reset Button on your Arduino to restart the example execution once you have the sensor supply voltage plugged back in.

Contributing

Contributions are welcome!

We develop and test this driver using our company internal tools (version control, continuous integration, code review etc.) and automatically synchronize the master branch with GitHub. But this doesn't mean that we don't respond to issues or don't accept pull requests on GitHub. In fact, you're very welcome to open issues or create pull requests :)

This Sensirion library uses clang-format to standardize the formatting of all our .cpp and .h files. Make sure your contributions are formatted accordingly:

The -i flag will apply the format changes to the files listed.

clang-format -i src/*.cpp src/*.h

Note that differences from this formatting will result in a failed build until they are fixed.

License

See LICENSE.