URGENT: Capturing data through serial port

Question

Hi,
My problem is with the use of javax.comm API. I have an RFID tag reader connected to
the serial port. It is a handheld reader and reads tags when its trigger is pulled. The
data that is read is sent to the serial port. This is what I want to capture.
I tried to test the reading operation by running the SimpleRead sample. What I see is
that I pull the trigger once to read 1 tag, but that generates 3 DATA_AVAILABLE events.
The tag ID that is read is 16 bytes, preceded by a 3 byte AIM Identifier (that declares
the following data was read from an RFID tag, and not a barcode which has different
AIM Identifiers for the different symbologies - but I digress.) By inserting some println's,
I was able to see that the 19 bytes of data are read 8 bytes at a time. The first 8 bytes
are read on the first DATA_AVAILABLE event, the next 8 are read on the second event
and the last 3 bytes are read on the 3rd DATA_AVAILABLE event.
This is strange & not good for me. How can my application know that the data read in
these 3 separate DATA_AVAILABLE events is to be concatenated to form a single
tag ID? Why is the single trigger-pull & tag read operation broken up into chunks of
8 bytes? Is there some configuration setting that will give me the behavior I want?
(I cannot rely on the length of the tag ID being 16 bytes always, because the same
reader will also be reading barcodes where the data may have varying length)
Thanks for any help. This is really urgent.
- Ajoy

Answer 1

please use the [ code ]and [code ] tags for code.
I don't think you have a problem with the code, it's more like understanding how to make it work.
to make the read method return.You do not have a read() method.
The code is behaving as it should.
You need to use the SimpleRead class as a thread, add and remove the Serial port listener as needed.
You read all data available, then send it to a method to parse the buffer.
You can count how much data was read so you know how much to parse.
I never used receive threshhold.
Here is example (sample)of my serial port reader
//SerialIO
   public void serialEvent(SerialPortEvent event) {
        switch(event.getEventType()) {
              case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
            break;
        case SerialPortEvent.DATA_AVAILABLE:
            this.dataManager.readData();
//DataManager
public void readData() {
     String str;
     int     bytes = 0;
     long endTime, now;
     try {
          while (this.owner.isComPortOpen
               && (SerialIO.inStream.available() > 0)) {
               bytes = SerilIO.inStream.read(this.buffer);
               if (bytes > 0) {
               if (bytes > this.buffer.length) {
                    System.out.println( ": Input buffer overflow!");
     **Here is where you parse your buffer
               sendDataToParser(bytes, buffer);
          } catch (IOException ex) {
               System.out.println( ": Cannot read input stream");
      * Stops the serialEvent listener
     protected void stopSerialEvent() {
          SerialIO.serialPort.removeEventListener();
          try {
               Thread.sleep(2000);
               flushInputStream();
          } catch (InterruptedException e1) {
               // TODO Auto-generated catch block
               e1.printStackTrace();
      * Starts the Serial event listener
     protected void startSerialEvent() {
          // TODO Auto-generated method stub
          try {
               SerialIO.serialPort.addEventListener(SerialIO);
          } catch (TooManyListenersException e) {
               // TODO Auto-generated catch block
               //System.out.println("startSerialEvent in dataManager");
               e.printStackTrace();