Sensor.java

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package iotdevice;

import com.pi4j.io.i2c.I2CBus;
import com.pi4j.io.i2c.I2CDevice;
import com.pi4j.io.i2c.I2CFactory;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
//import com.pi4j.io.i2c.
import java.io.IOException;

/**
 *
 * @author Matteo
 */
public class Sensor {

    //Raspberry Pi's I2C bus
    private static final int i2cBus = 1;
    // Device address
    // private static final int address = 0x50;
    // RFID read address
    private static final int rfidAddrRead = 0xA1;
    private static final int rfidAddrWrite = 0xA0;
    // Read RFID command
    private static final byte getRfidCmd = (byte) 0x01;
    private static final byte firmwareRfidCmd = (byte) 0xF0;

    //I2C bus
    I2CBus bus;
    // Device object
    private I2CDevice sl030Read;
    private I2CDevice sl030Write;
    private DataInputStream sl030CalIn;
    private DataInputStream sl030In;

    public Sensor() {

        try {
            bus = I2CFactory.getInstance(I2CBus.BUS_1);
            System.out.println("Connected to bus OK!!!");

            //get device itself
            sl030Read = bus.getDevice(rfidAddrRead);
            sl030Write = bus.getDevice(rfidAddrWrite);
            System.out.println("Connected to device OK!!!");
            //Small delay before starting
           // Thread.sleep(500);
                 } catch (IOException e) {
            System.out.println("Exception: " + e.getMessage());
                 }
    }

    public String readRfid() throws IOException {

        byte[] bytesTemp = new byte[4];
        byte[] towrite= new byte[2];
        String result="EMPTY";
        try {
            towrite[0]=(byte)0x01;
            towrite[1]=firmwareRfidCmd;
            sl030Write.write(towrite,0,2);
            Thread.sleep(1000);
           // sl030.r
            int readTotal = sl030Read.read(bytesTemp, 0, 4);
            System.out.println("Letti: " +readTotal);
//            if (readTotal < 2) {
//                System.out.format("Error: %n bytes read/n", readTotal);
//                return "EMPTY";
//            }
//            //sl030In = new DataInputStream(new ByteArrayInputStream(bytesTemp));
//            //UT = sl030In.readUnsignedShort();
            result = new String(bytesTemp);
        } catch (IOException e) {
            System.out.println("Error: " + e.getMessage());
        } catch (InterruptedException e) {
            System.out.println("Interrupted Exception: " + e.getMessage());
        }
     //   System.out.println("Id RFID: " + result);
        return result;
    }

}