Sensirion UART SVM4X Arduino Library

This is the Sensirion SVM4X library for Arduino allowing you to communicate with a SVM4X evaluation kit over UART using the SHDLC protocol.

Click here to learn more about the Sensirion SVM4X evaluation kit.

The SVM4x evaluation kit covers evaluation of the SGP40 and SGP41 sensors. This driver supports SVM4x firmware version 3.1.0 and above.

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 Sensirion UART SVM4X 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

Connecting the Sensor

Use the following pin description to connect your SVM4X to your Arduino board:

Pin	Cable Color	Name	Description	Comments
1	red	VDD	Supply Voltage	3.3 or 5V
2	black	GND	Ground
3	green	RX	UART: Transmission pin for communication
4	yellow	TX	UART: Receiving pin for communication
5	blue	SEL	Interface select	Leave floating or pull to VDD to select UART
6	purple	NC	Do not connect

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 SVM4X 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

SVM4X	SVM4X Pin	Cable Color	Board Pin
VDD	1	red	5V
GND	2	black	GND
RX	3	green	D18 (TX1)
TX	4	yellow	D19 (RX1)
SEL	5	blue	Do not connect

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

Espressif ESP32-DevKitC Pinout

SVM4X	SVM4X Pin	Cable Color	Board Pin
VDD	1	red	5V
GND	2	black	GND
RX	3	green	GPIO17 (TXD 2)
TX	4	yellow	GPIO16 (RXD 2)
SEL	5	blue	Do not connect

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

Quick start example

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

2. Connect the SVM4X sensor as explained in Sensor wiring

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

   File ➔ Examples ➔ Sensirion UART SVM4X ➔ 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 SVM4X 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 Espressif 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 include 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.