java arduino serial communication

Question

I am trying to set up a java-arduino serial communication. So far I downloaded the code from the Arduino page (http://playground.arduino.cc/interfacing/java) but I get an error. Code:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier; 
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent; 
import gnu.io.SerialPortEventListener; 
import java.util.Enumeration;


public class SerialTest implements SerialPortEventListener {
    SerialPort serialPort;
        /** The port we're normally going to use. */
    private static final String PORT_NAMES[] = { 
            "/dev/tty.usbserial-A9007UX1", // Mac OS X
                        "/dev/ttyACM0", // Raspberry Pi
            "/dev/ttyUSB0", // Linux
            "COM3", // Windows
    };
    /**
    * A BufferedReader which will be fed by a InputStreamReader 
    * converting the bytes into characters 
    * making the displayed results codepage independent
    */
    private BufferedReader input;
    /** The output stream to the port */
    private OutputStream output;
    /** Milliseconds to block while waiting for port open */
    private static final int TIME_OUT = 2000;
    /** Default bits per second for COM port. */
    private static final int DATA_RATE = 9600;

    public void initialize() {
                // the next line is for Raspberry Pi and 
                // gets us into the while loop and was suggested here was suggested http://www.raspberrypi.org/phpBB3/viewtopic.php?f=81&t=32186
                System.setProperty("gnu.io.rxtx.SerialPorts", "/dev/ttyACM0");

        CommPortIdentifier portId = null;
        Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();

        //First, Find an instance of serial port as set in PORT_NAMES.
        while (portEnum.hasMoreElements()) {
            CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
            for (String portName : PORT_NAMES) {
                if (currPortId.getName().equals(portName)) {
                    portId = currPortId;
                    break;
                }
            }
        }
        if (portId == null) {
            System.out.println("Could not find COM port.");
            return;
        }

        try {
            // open serial port, and use class name for the appName.
            serialPort = (SerialPort) portId.open(this.getClass().getName(),
                    TIME_OUT);

            // set port parameters
            serialPort.setSerialPortParams(DATA_RATE,
                    SerialPort.DATABITS_8,
                    SerialPort.STOPBITS_1,
                    SerialPort.PARITY_NONE);

            // open the streams
            input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
            output = serialPort.getOutputStream();

            // add event listeners
            serialPort.addEventListener(this);
            serialPort.notifyOnDataAvailable(true);
        } catch (Exception e) {
            System.err.println(e.toString());
        }
    }

    /**
     * This should be called when you stop using the port.
     * This will prevent port locking on platforms like Linux.
     */
    public synchronized void close() {
        if (serialPort != null) {
            serialPort.removeEventListener();
            serialPort.close();
        }
    }

    /**
     * Handle an event on the serial port. Read the data and print it.
     */
    public synchronized void serialEvent(SerialPortEvent oEvent) {
        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                String inputLine=input.readLine();
                System.out.println(inputLine);
            } catch (Exception e) {
                System.err.println(e.toString());
            }
        }
        // Ignore all the other eventTypes, but you should consider the other ones.
    }

    public static void main(String[] args) throws Exception {
        SerialTest main = new SerialTest();
        main.initialize();
        Thread t=new Thread() {
            public void run() {
                //the following line will keep this app alive for 1000 seconds,
                //waiting for events to occur and responding to them (printing incoming messages to console).
                try {Thread.sleep(1000000);} catch (InterruptedException ie) {}
            }
        };
        t.start();
        System.out.println("Started");
    }
}

That's the output i get:

Stable Library ========================================= Native lib Version = RXTX-2.2pre2 Java lib Version = RXTX-2.1-7 WARNING: RXTX Version mismatch Jar version = RXTX-2.1-7 native lib Version = RXTX-2.2pre2
Could not find COM port. Started

I am using Linux. And I think the port is correct. Anyone could help?

Answer 1

After seeing the problems and struggling with RXTX and JSSC for while, I developed the JAVA Arduino Communication Library.

My library has (hopefullyy) great documentation(found on the SourceForge Wiki for the library) and tells you exactly how to install and use it. After downloading both JARs in the library and including them in your classpath, just include the following statement before your class definition:

import arduino.*;

Now, all you need is the following code snippet in your method, and you're good to go!

String ArduinoPort = ""; //Your port name here
int BAUD_RATE = 9600;
Arduino arduino = new Arduino(ArduinoPort, BAUD_RATE);
arduino.openConnection(); 
arduino.serialWrite('1'); //serialWrite is an overridden method, allowing both characters and strings.
arduino.serialWrite('1', 20); //its second parameter even allows delays. more details can be found in the documentation.

The library also comes with example code that I thought would help speed along the process.

Answer 2

it seems to be permission issue. try : sudo chmod 666 /dev/ttyACM0 (you usb ) and rerun the java code again.

Answer 3

"Could Not Find Com Port" is the default error for when your Arduino can't interface with Arduino IDE.

In this case though, the error isn't saying that the Arduino IDE can't see your Arduino - its saying that the RXTX library can't see the Arduino.

Your PC's driver may be an older version, and not yet support the com required by RXTX...

Here's my advice:

Plugin your Arduino Board

Go to Control Panel ---> System and Security ---> System ---> On the left pane Device Manger

Expand Other Devices.

Under Other Devices you will notice a icon with a small yellow error graphic. (Unplug all your other devices attached to any Serial Port)

Right Click on that device ---> Update Driver Software

Select Browse my computer for Driver Software

Click on Browse ---> Browse for the folder of Arduino Environment which you have downloaded from Arduino website. If not downloaded then http://arduino.cc/en/Main/Software

After Browsing mark include subfolder.

Click next ---> Your driver will be installed.

Collapse Other Devices ---> Expand Port ( its in device manager only under other devices )

You will see Arduino Written ---> Look for its COM PORT (close device manager)

Go to Arduino Environment ---> Tools ---> Serial Port ---> Select the COM PORT as mentioned in PORT in device manager. (If you are using any other Arduino Board instead of UNO then select the same in boards )

Some Reference Material: http://www.devfactor.net/2014/10/26/arduino-basics-serial-communication/