Arduino Due and Si7021 temperature sensor example

The  Si7021  I2C Humidity  and  Temperature  Sensor  is  a  monolithic  CMOS  IC integrating   humidity   and   temperature   sensor   elements,   an   analog-to-digital converter, signal processing, calibration data, and an I2C Interface. The Si7021 offers an accurate, low-power, factory-calibrated digital solution ideal for measuring humidity, dew-point, and temperature, in applications ranging from HVAC/R and asset tracking to industrial and consumer platforms.

Features

Precision Relative Humidity Sensor ± 3% RH (max), 0–80% RH
High Accuracy Temperature Sensor ±0.4 °C (max), –10 to 85 °C
0 to 100% RH operating range
Up to –40 to +125 °C operating range
Wide operating voltage – (1.9 to 3.6 V)
Low Power Consumption – 150 μA active current

Layout

Code

No 3rd party libraries required

[codesyntax lang=”cpp”]

#include <Wire.h>
 
const int ADDR =0x40;
int X0,X1,Y0,Y1,Y2,Y3;
double X,Y,X_out,Y_out1,Y_out2;
 
void setup()
{ 
  Serial.begin(9600);   
  Wire.begin();                                   
  delay(100);  
  Wire.beginTransmission(ADDR);
  Wire.endTransmission();                        
}
 
void loop()
{
  /**Send command of initiating temperature measurement**/
  Wire.beginTransmission(ADDR);
  Wire.write(0xE3);
  Wire.endTransmission();
 
  Serial.print("Temp");
  Serial.print("\t");
  Serial.println("Humidity");
 
  /**Read data of temperature**/
  Wire.requestFrom(ADDR,2);
 
  if(Wire.available()<=2);
  {
    X0 = Wire.read();
    X1 = Wire.read();
    X0 = X0<<8;
    X_out = X0+X1;
  }
 
  /**Calculate and display temperature**/
  X=(175.72*X_out)/65536;                        
  X=X-46.85;
  Serial.print(X);
  Serial.print("C");
  Serial.print("\t");
 
  /**Send command of initiating relative humidity measurement**/
  Wire.beginTransmission(ADDR);                     
  Wire.write(0xE5);
  Wire.endTransmission(); 
 
  /**Read data of relative humidity**/
  Wire.requestFrom(ADDR,2);
  if(Wire.available()<=2);
  {
    Y0 = Wire.read();
    Y2=Y0/100; 
    Y0=Y0%100;
    Y1 = Wire.read();
    Y_out1 = Y2*25600;
    Y_out2 = Y0*256+Y1;
  }
 
  /**Calculate and display relative humidity**/
  Y_out1 = (125*Y_out1)/65536;                     
  Y_out2 = (125*Y_out2)/65536;
  Y = Y_out1+Y_out2;
  Y=Y-6;
  Serial.print(Y);
  Serial.println("%");                     
 delay(300);
 
 
Serial.println(); 
delay(1000);
 
}

[/codesyntax]

Testing

Open the serial monitor and you should see something like this

Temp Humidity
21.02C 37.63%

Temp Humidity
21.76C 37.93%

Temp Humidity
26.21C 39.49%

Temp Humidity
28.65C 40.68%

Temp Humidity
29.88C 41.89%

Temp Humidity
29.51C 42.16%

Link

Si7021 Humidity Sensor with I2C Interface for Arduino