Example code to deal with the TMP102 Temp Sensor via the PI4J API on a RaspberryPi.

TMP102.java

import com.pi4j.io.i2c.I2CBus;
import com.pi4j.io.i2c.I2CDevice;
import com.pi4j.io.i2c.I2CFactory;
import com.pi4j.system.SystemInfo;
import com.pi4j.temperature.TemperatureConversion;
import com.pi4j.temperature.TemperatureScale;
import java.io.IOException;

/**
 *
 * @author Mark de Reeper
 */
public class TMP102 {

    /**
     * http://www.zagrosrobotics.com/files/tmp102.pdf
     * 
       DEVICE TWO-WIRE ADDRESS  A0 PIN CONNECTION
            1001000 (0x48)      Ground
            1001001 (0x49)      V+
            1001010 (0x4A)      SDA
            1001011 (0x4B)      SCL
     */
    public static final int DEVICE_ADDRESS_GROUND = 0x48;
    public static final int DEVICE_ADDRESS_VPLUS = 0x49;
    public static final int DEVICE_ADDRESS_SDA = 0x4A;
    public static final int DEVICE_ADDRESS_SCL = 0x4B;

    private I2CBus bus = null;
    private I2CDevice device = null;
    

    public TMP102(int sensorAddress) throws IOException, InterruptedException {

        if (SystemInfo.getBoardType().equals(SystemInfo.BoardType.ModelA_Rev0)) {
            bus = I2CFactory.getInstance(I2CBus.BUS_0);
        } else {
            bus = I2CFactory.getInstance(I2CBus.BUS_1);
        }
        
        if (bus != null) {
            device = bus.getDevice(sensorAddress);
        }
    }

    public double getTemperature(TemperatureScale scale) throws IOException {
        
        // default is Celsius
        double result = getReadingFromDevice() * 0.0625;

        switch (scale) {
            case CELSIUS :
                break;
            case FARENHEIT :
                result = TemperatureConversion.convertCelsiusToFarenheit(result);
                break;
            case KELVIN :
                result = TemperatureConversion.convertCelsiusToKelvin(result);
                break;
            case RANKINE :
                result = TemperatureConversion.convertCelsiusToRankine(result);
                break;
        }

        return result;
    }

    private void close() throws IOException {
        
        if (bus != null) {
            bus.close();
        }
    }

    private int getReadingFromDevice() throws IOException {

        int result = 0;

        if (device != null) {
            // http://www.raspberrypi.org/phpBB3/viewtopic.php?f=81&t=31272
            // http://bildr.org/2011/01/tmp102-arduino/
            byte[] tempBuffer = new byte[2];
            int bytesRead = device.read(tempBuffer, 0, 2);
            if (bytesRead == 2) {
                int MSB = tempBuffer[0] < 0 ? 256 + tempBuffer[0] : tempBuffer[0];
                int LSB = tempBuffer[1] < 0 ? 256 + tempBuffer[1] : tempBuffer[1];
                
                result = ((MSB << 8) | LSB) >> 4;
            }
        }
        
        return result;
    }
}