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PORXTX two way serial communication doesn't send data after first run
 

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    <p>I edited an already-made example from the RXTX website. I am new in Java and Serial comm programming too.</p> <p>The app runs perfectly one time. It reads the buffer from the PIC and sends the number I enter. The LEDs light and the PIC sends back the same buffer, asking for a number. But when I enter it, the LEDs turn off, nothing lights up again and I get again the message asking for a number.</p> <p>There is nothing wrong with the micro controller's soft as it works perfectly with HyperTerminal. </p> <p>The code is below:</p> <pre><code>import gnu.io.CommPort; import gnu.io.CommPortIdentifier; import gnu.io.SerialPort; import gnu.io.SerialPortEvent; import gnu.io.SerialPortEventListener; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; /** * This version of the TwoWaySerialComm example makes use of the * SerialPortEventListener to avoid polling. * */ public class Test { public Test() { 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(9600,SerialPort.DATABITS_8,SerialPort.STOPBITS_1,SerialPort.PARITY_NONE); InputStream in = serialPort.getInputStream(); OutputStream out = serialPort.getOutputStream(); serialPort.addEventListener(new SerialReader(in)); serialPort.notifyOnDataAvailable(true); (new Thread(new SerialWriter(out))).start(); } else { System.out.println("Error: Only serial ports are handled by this example."); } } } /** * Handles the input coming from the serial port. A new line character * is treated as the end of a block in this example. */ public static class SerialReader implements SerialPortEventListener { private InputStream in; private byte[] buffer = new byte[1024]; public SerialReader ( InputStream in ) { this.in = in; } public void serialEvent(SerialPortEvent arg0) { int data; try { int len = 0; while ( ( data = in.read()) &gt; -1 ) { if ( data == '\n' ) { break; } buffer[len++] = (byte) data; } System.out.print(new String(buffer,0,len)); } catch ( IOException e ) { e.printStackTrace(); System.exit(-1); } } } /** */ 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()) &gt; -1 ) { this.out.write(c); } } catch ( IOException e ) { e.printStackTrace(); System.exit(-1); } } } public static void main ( String[] args ) { try { (new Test()).connect("COM3"); } catch ( Exception e ) { // TODO Auto-generated catch block e.printStackTrace(); } } } </code></pre>
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    1. COI found out that from the second run the Java app adds a new line to the string sent to the PIC. For example instead of `2`, it sends `[new line]2`
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    2. COYou should probably specify exactly which version of RXTX you are using and on what OS you are running. There have been issues related to non-blocking receive events. Example: http://stackoverflow.com/questions/1391946/is-constant-polling-in-rxtx-necessary
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    3. COAfter reading your 1st comment, it occurred to me that perhaps you don't realize the `this.out.write(c);` will be sending the enter key press (\n) in addition to the character that you type. As a result and depending on how your PIC is coded, perhaps that is messing up the second "run". (And by "run", I think you mean the second loop.)
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