Conexão Porta Serial em Java

jSSC - java-simple-serial-connector
http://code.google.com/p/java-simple-serial-connector/

alternativa ao java rxtx usado no arduino

código mais simples, exemplo

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import jssc.SerialPort;

import jssc.SerialPortException;

public class Main {

public static void main(String[] args) {

SerialPort serialPort = new SerialPort("COM1");

try {

//Open serial port

serialPort.openPort();

//Set params.

serialPort.setParams(9600, 8, 1, 0);

//Read 10 bytes from serial port

byte[] buffer = serialPort.readBytes(10);

serialPort.closePort();//Close serial port

}

catch (SerialPortException ex) {

System.out.println(ex);

}

}

}

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