In this post I expect to explain how to use Java RxTx library to carry out a two way serial communication with an Arduino. On downloading and installing Java RxTx serial communication library please refer this link
http://duvindu92.blogspot.com/2013/07/installing-java-rxtx-library-for-serial.html.
In this sample code first a string is sent by the Arduino requesting the name of the user. Once the user types in the name, it is sent back to the Arduino through the serial port and Arduino returns a welcome message, "Hello"+ <yourName>. So lets begin
The JAVA Code
import java.io.BufferedReader; //BufferedReader makes reading operation efficient
import java.io.InputStreamReader; //InputStreamReader decodes a stream of bytes into a character set
import java.io.OutputStream; //writes stream of bytes into serial port
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent; //deals with possible events in serial port (eg: data received)
import gnu.io.SerialPortEventListener; //listens to the a possible event on serial port and notifies when it does
import java.util.Enumeration;
import gnu.io.PortInUseException; //all the exceptions.Never mind them for now
import java.io.IOException;
import gnu.io.UnsupportedCommOperationException;
import java.util.TooManyListenersException;
import java.util.Scanner; //to get user input of name
public class SerialTest implements SerialPortEventListener {
private SerialPort serialPort ; //defining serial port object
private CommPortIdentifier portId = null; //my COM port
private static final int TIME_OUT = 2000; //time in milliseconds
private static final int BAUD_RATE = 9600; //baud rate to 9600bps
private BufferedReader input; //declaring my input buffer
private OutputStream output; //declaring output stream
private String name; //user input name string
Scanner inputName; //user input name
//method initialize
private void initialize(){
CommPortIdentifier ports = null; //to browse through each port identified
Enumeration portEnum = CommPortIdentifier.getPortIdentifiers(); //store all available ports
while(portEnum.hasMoreElements()){ //browse through available ports
ports = (CommPortIdentifier)portEnum.nextElement();
//following line checks whether there is the port i am looking for and whether it is serial
if(ports.getPortType() == CommPortIdentifier.PORT_SERIAL&&ports.getName().equals("COM6")){
System.out.println("COM port found:COM6");
portId = ports; //initialize my port
break; }
}
//if serial port am looking for is not found
if(portId==null){
System.out.println("COM port not found");
System.exit(1);
}
}
//end of initialize method
//connect method
private void portConnect(){
//connect to port
try{
serialPort = (SerialPort)portId.open(this.getClass().getName(),TIME_OUT); //down cast the comm port to serial port
//give the name of the application
//time to wait
System.out.println("Port open succesful: COM6");
//set serial port parameters
serialPort.setSerialPortParams(BAUD_RATE,SerialPort.DATABITS_8,SerialPort.STOPBITS_1,SerialPort.PARITY_NONE);
}
catch(PortInUseException e){
System.out.println("Port already in use");
System.exit(1);
}
catch(NullPointerException e2){
System.out.println("COM port maybe disconnected");
}
catch(UnsupportedCommOperationException e3){
System.out.println(e3.toString());
}
//input and output channels
try{
//defining reader and output stream
input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
output = serialPort.getOutputStream();
//adding listeners to input and output streams
serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);
serialPort.notifyOnOutputEmpty(true);
}
catch(Exception e){
System.out.println(e.toString());
}
}
//end of portConncet method
//readWrite method
public void serialEvent(SerialPortEvent evt) {
if (evt.getEventType() == SerialPortEvent.DATA_AVAILABLE) { //if data available on serial port
try {
String inputLine=input.readLine();
System.out.println(inputLine);
inputName = new Scanner(System.in); //get user name
name = inputName.nextLine();
name = name + '\n';
System.out.printf("%s",name);
output.write(name.getBytes()); //sends the user name
} catch (Exception e) {
System.err.println(e.toString());
}
}
}
//end of serialEvent method
//closePort method
private void close(){
if(serialPort!=null){
serialPort.close(); //close serial port
}
input = null; //close input and output streams
output = null;
}
//main method
public static void main(String[] args) {
SerialTest myTest = new SerialTest(); //creates an object of the class
myTest.initialize();
myTest.portConnect();
System.out.println("Started");
while(1>0); //wait till any activity
}
//end of main method
// end of SerialTest class
}
Arduino Code
boolean stringComplete = false;
String inputString = "";
int led=13;
void setup(){
Serial.begin(9600);
pinMode(led,OUTPUT);
Serial.println("Hi, What's Your Name");
}
void serialEvent() {
while (Serial.available()) {
char inChar = (char)Serial.read();
inputString += inChar;
if (inChar == '\n') {
stringComplete = true;
}
Serial.flush();
//end of while()
}
//end of serialEvent
}
void loop(){
if(stringComplete){
digitalWrite(led,HIGH);
String name = "Hello "+ inputString;
inputString = "";
Serial.println(name);
stringComplete = false;
}
}
