how to write on rs232 connection

Question

I'm developing a little software that need a connection rs232 with a peripheral...

I have downloaded the latest versione of RXTX library and, from the same site, using the class TwoWaySerialComm to communicate through the serial cable

http://rxtx.qbang.org/wiki/index.php/Event_based_two_way_Communication

import gnu.io.CommPort;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;

import java.io.FileDescriptor;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class TwoWaySerialComm
{
    public TwoWaySerialComm()
    {
        super();
    }

    void connect ( String portName ) throws Exception
    {
        CommPortIdentifier portIdentifier = CommPortIdentifier.getPortIdentifier(portName);
        if ( portIdentifier.isCurrentlyOwned() )
        {
            System.out.println("Error: Port is currently in use");
        }
        else
        {
            CommPort commPort = portIdentifier.open(this.getClass().getName(),2000);

            if ( commPort instanceof SerialPort )
            {
                SerialPort serialPort = (SerialPort) commPort;
                serialPort.setSerialPortParams(57600,SerialPort.DATABITS_8,SerialPort.STOPBITS_1,SerialPort.PARITY_NONE);

                InputStream in = serialPort.getInputStream();
                OutputStream out = serialPort.getOutputStream();

                (new Thread(new SerialReader(in))).start();
                (new Thread(new SerialWriter(out))).start();

            }
            else
            {
                System.out.println("Error: Only serial ports are handled by this example.");
            }
        }     
    }

    /** */
    public static class SerialReader implements Runnable 
    {
        InputStream in;

        public SerialReader ( InputStream in )
        {
            this.in = in;
        }

        public void run ()
        {
            byte[] buffer = new byte[1024];
            int len = -1;
            try
            {
                while ( ( len = this.in.read(buffer)) > -1 )
                {
                    System.out.print(new String(buffer,0,len));
                }
            }
            catch ( IOException e )
            {
                e.printStackTrace();
            }            
        }
    }

    /** */
    public static class SerialWriter implements Runnable 
    {
        OutputStream out;

        public SerialWriter ( OutputStream out )
        {
            this.out = out;
        }

        public void run ()
        {
            try
            {                
                int c = 0;
                while ( ( c = System.in.read()) > -1 )
                {
                    this.out.write(c);
                }                
            }
            catch ( IOException e )
            {
                e.printStackTrace();
            }            
        }
    }

    public static void main ( String[] args )
    {
        try
        {
            (new TwoWaySerialComm()).connect("COM3");
        }
        catch ( Exception e )
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

Now supposedly I have to send text "STX 1000 T ETX" to the device, how do I do that?

Thanks

Answer 1

The example you followed is for writing everything you type in to the console (System.in), out to the serial port. You will need to modify your program so that you can output specific strings instead of whatever you type in. The possible solutions are too varied to provide an answer here, and it requires you have at least some background in Java programming.

As a start though, consider creating a new class something like this:

public class MyCustomSerialWriter
{
    OutputStream out;

    public SerialWriter ( OutputStream out )
    {
        this.out = out;
    }

    public void writeString (String str)
    {
        try {
            this.out.write(str.getBytes(Charset.forName("ASCII"));
        }
        catch ( IOException e )
        {
            e.printStackTrace();
        }            
    }
}

You can then call it from your main method to output whatever string you would like.