Raspberry Pi and SHT31 humidity sensor java example

In this example we will connect an SHT31 humidity sensor to a Raspberry Pi and use Java to display the temperature readings, there are other languages such as C and python which work as well but I wanted to try something a little different

The new digital SHT3x humidity sensor series takes sensor technology to a new level. As the successor of the SHT2x series it is determined to set the next industry standard in humidity sensing. The SHT3x humidity sensor series consists of a low-cost version with the SHT30 humidity sensor, a standard version with the SHT31 humidity sensor, and a high-end version with the SHT35 humidity sensor. The SHT3x humidity sensor series combines multiple functions and various interfaces (I2C, analog voltage output) with a applications-friendly, very wide operating voltage range (2.4 to 5.5 V). The SHT3x humidity sensor is available in both large and small volumes.

The SHT3x builds on a completely new and optimized CMOSens® chip, which allows for increased reliability and improved accuracy specifications. The SHT3x offers a range of new features, such as enhanced signal processing, two distinctive and user-selectable I2C addresses, an alert mode with programmable humidity and temperature limits, and communication speeds of up to 1 MHz.

You can read more – https://www.sensirion.com/en/environmental-sensors/humidity-sensors/digital-humidity-sensors-for-various-applications/

 

Parts List

 

Label Part Type
Part2 Adafruit SHT31-D Sensirion Temperature/Humidity Sensor
Raspberry Pi1 Raspberry Pi 2

Layout

 

 

Code

This time we explore the world of Java on the Raspberry Pi

First you need to install PI4j – http://pi4j.com/install.html . I’ll sum it up as its easy to install from a terminal

The simplest method to install Pi4J on your RaspberryPi is to execute the following command directly on your RaspberryPi.
curl -s get.pi4j.com | sudo bash

Now for the java code – this is courtesy of a controleverything example

// 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.
// SHT31
// This code is designed to work with the SHT31_I2CS I2C Mini Module available from ControlEverything.com.
// https://www.controleverything.com/content/Humidity?sku=SHT31_I2CS#tabs-0-product_tabset-2
 
import com.pi4j.io.i2c.I2CBus;
import com.pi4j.io.i2c.I2CDevice;
import com.pi4j.io.i2c.I2CFactory;
import java.io.IOException;
 
public class SHT31
{
	public static void main(String args[]) throws Exception
	{
		// Create I2CBus
		I2CBus bus = I2CFactory.getInstance(I2CBus.BUS_1);
		// Get I2C device, SHT31 I2C address is 0x44(68)
		I2CDevice device = bus.getDevice(0x44);
 
		// Send high repeatability measurement command
		// Command msb, command lsb
		byte[] config = new byte[2];
		config[0] = (byte)0x2C; 
		config[1] = (byte)0x06;
		device.write(config, 0, 2);
		Thread.sleep(500);
 
		// Read 6 bytes of data
		// temp msb, temp lsb, temp CRC, humidity msb, humidity lsb, humidity CRC
		byte[] data = new byte[6];
		device.read(data, 0, 6);
 
		//Convert the data
		double cTemp = ((((data[0] & 0xFF) * 256) + (data[1] & 0xFF)) * 175.0) / 65535.0  - 45.0;
		double fTemp = ((((data[0] & 0xFF) * 256) + (data[1] & 0xFF)) * 315.0) / 65535.0 - 49.0;
		double humidity = ((((data[3] & 0xFF) * 256) + (data[4] & 0xFF)) * 100.0) / 65535.0;
 
		//Output data to screen
		System.out.printf("Temperature in Celsius : %.2f C %n", cTemp);
		System.out.printf("Temperature in Fahrenheit : %.2f F %n", fTemp);
		System.out.printf("Relative Humidity is : %.2f %%RH %n", humidity);
	}
}

 

Now you have to compile and run the program like this

$> sudo pi4j SHT31.java

Testing

You should see the following

sht31 output
sht31 output

 

Links

1PCS/LOT SHT31 Temperature & SHT31-D Humidity Sensor module Breakout Weather for Arduino