Linux – Using USB to Serial in Ubuntu 12.04 – /dev/ttyUSB0 missing

There is a solution. It's better late then never ;)

Use the following udev rule to map /dev/ttyUSB{?} devices into the /dev/usb-ports/%bus_id-%port_id link.

Here is my /etc/udev/rules.d/usb-parse-devpath.rules:

ACTION=="add", KERNEL=="ttyUSB[0-9]*", PROGRAM="/etc/udev/rules.d/usb-parse-devpath.pm %p", SYMLINK+="usb-ports/%c"

And the usb-parse-devpath.pm script:

#!/usr/bin/perl -w

@items = split("/", $ARGV[0]);
for ($i = 0; $i < @items; $i++) {
    if ($items[$i] =~ m/^usb[0-9]+$/) {
        print $items[$i + 1] . "\n";
        last;
    }
}

As you can see this helps us to create named links to /dev/ttyUSB{?} devices and place them at /dev/usb-ports in the following format: bus_id-port_id.

For example, the next command gives me the following:

$ udevadm info --query=path --name=/dev/ttyUSB0
/devices/pci0000:00/0000:00:1d.1/usb3/3-1/3-1:1.0/ttyUSB0/tty/ttyUSB0

So, the bus_id is 3 and port_id is 1 and now I have following in my /dev/usb-ports:

$ ls -al /dev/usb-ports
lrwxrwxrwx  1 root root   10 Май 12 00:26 3-1 -> ../ttyUSB0

Regards.

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