Introduction: Arduino Nano - STS21 Temperature Sensor Tutorial

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STS21 Digital Temperature Sensor offers superior performance and a space saving footprint. It provides calibrated, linearized signals in digital, I2C format. Fabrication of this sensor is based on CMOSens technology, which attributes to the superior performance and reliability of STS21. The resolution of STS21 can be changed by command, low battery can be detected and a checksum helps to improve communication reliability. Here is its demonstration of interfacing it with Arduino nano.

Step 1: What You Need..!!

Step 2: Connection:

Take an I2C shield for Arduino Nano and gently push it over the pins of Nano.

Then connect the one end of I2C cable to STS21 sensor and the other end to the I2C shield.

Connections are shown in the picture above.

Step 3: Code:

The Arduino code for STS21 can be downloaded from our GitHub repository-Dcube Store.

Here is the link for the same :

We include library Wire.h to facilitate the I2c communication of the sensor with the Arduino board.

You can also copy the code from here, it is given as follows:

// Distributed with a free-will license.

// Use it any way you want, profit or free, provided it fits in the licenses of its associated works.

// STS21

// This code is designed to work with the STS21_I2CS I2C Mini Module available in Dcube Store.


// STS21 I2C address is 0x4A(74)

#define addr 0x4A

void setup()


// Initialise I2C communication as MASTER


// Start serial communication, set baud rate = 9600




void loop()


unsigned int data[2];

// Start I2C Transmission


// Select no hold master


// End I2C Transmission



// Request 2 bytes of data

Wire.requestFrom(addr, 2);

// Read 2 bytes of data

if (Wire.available() == 2)


data[0] =;

data[1] =;


// Convert the data

int rawtmp = data[0] * 256 + data[1];

int value = rawtmp & 0xFFFC;

double cTemp = -46.85 + (175.72 * (value / 65536.0));

double fTemp = cTemp * 1.8 + 32;

// Output data to serial monitor

Serial.print("Temperature in Celsius: ");


Serial.println(" C");

Serial.print("Temperature in Fahrenheit: ");


Serial.println(" F");



Step 4: Applications:

STS21 Digital Temperature Sensor can be employed in systems which require high accuracy temperature monitoring. It can be incorporated in various computer equipments, medical equipments and industrial control systems with the requisite of temperature measurement with proficient accuracy.