问题
I'm connecting a device with librxtx-java to Ubuntu. The code previously worked in 10.04, but in 12.04 it can't discover the usb-serial connected to the computer.
java.util.Enumeration<CommPortIdentifier> portEnum = CommPortIdentifier.getPortIdentifiers();
while ( portEnum.hasMoreElements() )
{
CommPortIdentifier portIdentifier = portEnum.nextElement();
System.out.println( portIdentifier.getName() + " - " + getPortTypeName(portIdentifier.getPortType()) );
}
This section of the code never goes into the while loop, despite the appropriate librxtx-java libraries being installed, and device being recognized (dmesg | tail shows USB "Serial Device converter detected" on one line).
Update:
It appears Ubuntu 12.04 64-bit isn't working with any usb-serial devices (although they show up in dmesg and show up as a /dev/ttyUSB, it seems to be more than just a problem with Java.
回答1:
I have Ubuntu 11.10 kernel 3.0.0-12-generic-pae and librxtx-java version 2.2pre2-8 installed. With the code below, it list my serial ports correctly. Now you have usb to serial converter installed properly? you need to check that what port is the converter use. Using the sample app below, you can try something like java -cp /usr/share/java/RXTXcomm.jar:. GetCommPorts 2
Please ensure that you have the correct permission in the ttySXX or ttyUSBXX file, in /dev/.
crw-rw---- 1 root dialout 4, 65 2012-02-29 01:08 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 2012-02-29 01:08 /dev/ttyS2
These serial ports are shown in my system and the user who want to run the application should be under group dialout. To add yourself, use:
sudo usermod -a -G dialout username
You should now be in "dialout" group.
import gnu.io.CommPortIdentifier;
import gnu.io.NoSuchPortException;
import gnu.io.PortInUseException;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent;
import gnu.io.SerialPortEventListener;
import gnu.io.UnsupportedCommOperationException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.TooManyListenersException;
public class GetCommPorts
{
static Enumeration<CommPortIdentifier> portList;
static CommPortIdentifier portId;
static SerialPort serialPort;
static OutputStream outputStream;
static boolean outputBufferEmptyFlag = false;
public static class SerialReader implements SerialPortEventListener
{
private InputStream in;
private byte[] buffer = new byte[1024];
public SerialReader(InputStream in)
{
this.in = in;
}
@Override
/**
* treat \n as end of block.
*/
public void serialEvent(SerialPortEvent ev)
{
int data;
try
{
int len = 0;
while ( (data = in.read()) > -1)
{
if (data == '\n')
{
break;
}
buffer[len++] = (byte) data;
}
System.out.println(new String(buffer, 0, len));
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
System.exit(-1);
}
}
}
public static class SerialWriter implements Runnable
{
OutputStream out;
public SerialWriter(OutputStream out)
{
this.out = out;
}
@Override
public void run()
{
try
{
int c = 0;
while ( (c = System.in.read()) > -1)
{
this.out.write(c);
}
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
System.exit(-1);
}
}
}
private static String getPortTypeName ( int portType )
{
switch ( portType )
{
case CommPortIdentifier.PORT_I2C:
return "I2C";
case CommPortIdentifier.PORT_PARALLEL:
return "Parallel";
case CommPortIdentifier.PORT_RAW:
return "Raw";
case CommPortIdentifier.PORT_RS485:
return "RS485";
case CommPortIdentifier.PORT_SERIAL:
return "Serial";
default:
return "unknown type";
}
}
private static void listPorts()
{
@SuppressWarnings("unchecked")
java.util.Enumeration<CommPortIdentifier> portEnum = CommPortIdentifier.getPortIdentifiers();
while ( portEnum.hasMoreElements() )
{
CommPortIdentifier portIdentifier = portEnum.nextElement();
System.out.println(portIdentifier.getName() + " - " + getPortTypeName(portIdentifier.getPortType()) );
if (portIdentifier.getPortType() == 1)
{
try
{
serialPort = (SerialPort) portIdentifier.open(portIdentifier.getName(), 3000);
}
catch (PortInUseException e)
{
System.err.print("port in use");
continue;
}
System.out.println("Baud is " + serialPort.getBaudRate());
System.out.println("Bits is " + serialPort.getDataBits());
System.out.println("Stop is " + serialPort.getStopBits());
System.out.println("Par is " + serialPort.getParity());
serialPort.close();
}
}
}
private static int doReadWrite(String portName)
{
CommPortIdentifier portIdentifier;
try
{
portIdentifier = CommPortIdentifier.getPortIdentifier(portName);
if (portIdentifier.isCurrentlyOwned())
{
System.err.println("error: port is currently in use");
return -1;
}
SerialPort sport = (SerialPort) portIdentifier.open(portName, 3000);
sport.setSerialPortParams(57600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
InputStream in = sport.getInputStream();
OutputStream out = sport.getOutputStream();
(new Thread(new SerialWriter(out))).start();
sport.addEventListener(new SerialReader(in));
sport.notifyOnDataAvailable(true);
}
catch (NoSuchPortException e)
{
e.printStackTrace();
return -1;
}
catch (PortInUseException e)
{
e.printStackTrace();
return -1;
}
catch (UnsupportedCommOperationException e)
{
e.printStackTrace();
return -1;
}
catch (IOException e)
{
e.printStackTrace();
return -1;
}
catch (TooManyListenersException e)
{
e.printStackTrace();
return -1;
}
return 0;
}
static void showHelp()
{
System.out.println("Usage " + GetCommPorts.class.getName() + "N");
System.out.println("1 read and write from the serial port");
System.out.println("2 list all serial ports in the system");
System.out.println("default show this help ");
}
public static void main(String[] args)
{
int operation = 0;
try
{
if (args.length != 1)
{
showHelp();
return;
}
operation = Integer.parseInt(args[0]);
}
catch (NumberFormatException e)
{
}
switch (operation)
{
case 1:
doReadWrite("/dev/ttyUSB0");
break;
case 2:
listPorts();
break;
default:
showHelp();
}
}
}
Output from this application:
$ java -cp /usr/share/java/RXTXcomm.jar:. GetCommPorts 2
/dev/ttyS1 - Serial
Baud is 9600
Bits is 8
Stop is 1
Par is 0
/dev/ttyS0 - Serial
Baud is 9600
Bits is 8
Stop is 1
Par is 0
来源：https://stackoverflow.com/questions/9628988/ubuntu-rxtx-does-not-recognize-usb-serial-device