Java Communications API

Question

Hi
I've written a program to communicate with a circuit with JCA throught LPT Port. I have done this:
import java.io.*;
import java.util.*;
import javax.comm.*;
public class test65{
static Enumeration portList;
static CommPortIdentifier portId;
static int num = 8;
static ParallelPort parPort;
static OutputStream outputStream;
public static void main(String arg[]){
portList = CommPortIdentifier.getPortIdentifiers();
while (portList.hasMoreElements()) {
portId = (CommPortIdentifier) portList.nextElement();
if (portId.getPortType() == CommPortIdentifier.PORT_PARALLEL) {
System.out.println ("Found Parralel Port :"+portId.getName());
if (portId.getName().equals("LPT1")) {
try {
parPort = (ParallelPort)portId.open("Robotics", 2000);
} catch (PortInUseException e) {
System.out.println("ERROR: This port is in use by: "+e.currentOwner+".");
try {
outputStream = parPort.getOutputStream();
} catch (IOException e) {
System.out.println ("ERROR: IO Exception.");
parPort.close();
} catch (NullPointerException e){
System.out.println ("ERROR: OutPutStream could not be Created.");
parPort.close();
try {
System.out.println ("Number "+num+" is about to be sent ....");
System.out.println ("Mode : "+parPort.getMode());
outputStream.write(num); //(1)
System.out.println ("Number "+num+" was Sent.");
} catch (IOException e) {
System.out.println ("ERROR: Could not Write Output");
parPort.close();
in the line that writes num to the stream,(1), program stops and doesn't send anything. If i install a printer then the num is sent to the printer driver to be PRINTED. i don't want to print anything. I've think if there is any driver that sends to the port whatever it recieves. What should i do to send numbers to LPT port like outp and out commands in basic and c ?

Answer 1

When using java communications api you need to simulate a centronics printer circuit in order to get output to the pins all this requires is that you pull pin11 (Busy) low, pin12 (Paper Out) low, and pin15 (Printer Error) High, although I've only had success thus far using spp mode which of course only supports output. Good luck all.