Introduction: Raspberry Pi MCP9805 Temperature Sensor Java Tutorial

MCP9805 is a memory module digital temperature sensor. It is incorporated with user programmable registers that provide flexibility for temperature sensing applications. This sensor is designed to be incorporated in mobile platform memory module temperature sensor. Here is the demonstration with a java code using Raspberry Pi.

Step 1: What You Need..!!

Picture of What You Need..!!

1. Raspberry Pi

2. MCP9805


3. I²C Cable

4. I²C Shield for Raspberry Pi


5. Ethernet Cable

Step 2: Connections

Picture of Connections

Take a I2C shield for raspberry pi and gently push it over the gpio pins of raspberry pi.

Then connect the one end of I2C cable to MCP9805 sensor and the other end to the I2C shield.

Also connect the Ethernet cable to the pi or you can use a WiFi module. Connections are shown in the picture above.

Step 3: Code

Picture of Code

The java code for MCP9805 can be downloaded from our github repository- ControlEverythingCommunity

Here is the link for the same :

The datasheet of MCP9805 can be found here:

We have used pi4j library for java code, the steps to install pi4j on raspberry pi is described here:

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.

// MCP9805

// This code is designed to work with the MCP9808_I2CS I2C Mini Module available from





public class MCP9805


public static void main(String args[]) throws Exception


// Create I2C bus

I2CBus Bus = I2CFactory.getInstance(I2CBus.BUS_1);

// Get I2C device, MCP9805 I2C address is 0x18(24)

I2CDevice device = Bus.getDevice(0x18);


// Select configuration register

// Continuous conversion mode, Power-up

byte[] config = new byte[2];

config[0] = 0x00;

config[1] = 0x00;

device.write(0x01, config, 0, 2);

// Select resolution rgister

// Resolution = +0.0625 / C

device.write(0x08, (byte)0x03);


// Read 2 bytes of data from address 0x05(05)

// temp msb, temp lsb

byte[] data = new byte[2];, data, 0, 2);

// Convert the data to 13-bits

int temp = ((data[0] & 0x1F) * 256 + (data[1] & 0xFF));

if(temp > 4095)


temp -= 8192;


double cTemp = temp * 0.0625;

double fTemp = cTemp * 1.8 + 32;

// Output data to screen

System.out.printf("Temperature in Celsius is : %.2f C %n", cTemp);

System.out.printf("Temperature in Fahrenheit is : %.2f F %n", fTemp);



Step 4: Applications..:

MCP9805 can be incorporated in various systems which include dual in-line memory module (DIMM) temperature monitoring systems, personal computers and servers. Commonly, it can be used as a general purpose temperature sensor.


About This Instructable



Bio: We are a group of makers. We work in IoT, IOS app, android app, embedded design, sensor design, raspberry pi, arduino, beaglebone, particle electron, particle ... More »
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