javax.usb：连接的设备数始终为零

Question

I have searched and searched SO, Google, etc. and everywhere I get code that is approximately similar to the one below. For example, I tried this . I tried running it with root and otherwise. But, the number of attached devices is always zero. Can you give me a clue as to why this could be happening ?

This is on Ubuntu-12.04, 32-bit.

Java code:

    package com.me.test;

    import java.io.UnsupportedEncodingException;
    import java.util.List;
    import javax.usb.UsbDevice;
    import javax.usb.UsbDisconnectedException;
    import javax.usb.UsbException;
    import javax.usb.UsbHostManager;
    import javax.usb.UsbHub;
    import javax.usb.UsbServices;

    public class ListUsbDevices {
        public static void main(String[] args) throws SecurityException, UsbException, UnsupportedEncodingException, UsbDisconnectedException {
            UsbServices services = UsbHostManager.getUsbServices();
            UsbHub rootHub = services.getRootUsbHub();

            List<UsbDevice> devices = rootHub.getAttachedUsbDevices();
            if (devices.size()>0) {
                System.out.println("USB devices found.");
            } else {
                System.out.println("No USB devices found.");
            }

            for (UsbDevice device : devices) {
                System.out.println("\tProduct String " + device.getProductString());
                System.out.println("\tManufacturer String " + device.getManufacturerString());
                System.out.println("\tSerial Number " + device.getSerialNumberString());
            }


        }
    }

lsusb output:

    user@host:~$ sudo lsusb
    Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 004 Device 010: ID 03eb:2013 Atmel Corp. 
    user@host:~$ sudo lsusb -s 4:10 -v
    Bus 004 Device 010: ID 03eb:2013 Atmel Corp. 
    Device Descriptor:
      bLength                18
      bDescriptorType         1
      bcdUSB               2.00
      bDeviceClass            0 (Defined at Interface level)
      bDeviceSubClass         0 
      bDeviceProtocol         0 
      bMaxPacketSize0        32
      idVendor           0x03eb Atmel Corp.
      idProduct          0x2013 
      bcdDevice           10.00
      iManufacturer           1 AppliedSensor
      iProduct                2 iAQ Stick
      iSerial                 0 
      bNumConfigurations      1
      Configuration Descriptor:
        bLength                 9
        bDescriptorType         2
        wTotalLength           41
        bNumInterfaces          1
        bConfigurationValue     1
        iConfiguration          0 
        bmAttributes         0x80
          (Bus Powered)
        MaxPower              100mA
        Interface Descriptor:
          bLength                 9
          bDescriptorType         4
          bInterfaceNumber        0
          bAlternateSetting       0
          bNumEndpoints           2
          bInterfaceClass         3 Human Interface Device
          bInterfaceSubClass      0 No Subclass
          bInterfaceProtocol      0 None
          iInterface              0 
            HID Device Descriptor:
              bLength                 9
              bDescriptorType        33
              bcdHID               1.11
              bCountryCode            0 Not supported
              bNumDescriptors         1
              bDescriptorType        34 Report
              wDescriptorLength      53
             Report Descriptors: 
               ** UNAVAILABLE **
          Endpoint Descriptor:
            bLength                 7
            bDescriptorType         5
            bEndpointAddress     0x81  EP 1 IN
            bmAttributes            3
              Transfer Type            Interrupt
              Synch Type               None
              Usage Type               Data
            wMaxPacketSize     0x0010  1x 16 bytes
            bInterval              10
          Endpoint Descriptor:
            bLength                 7
            bDescriptorType         5
            bEndpointAddress     0x02  EP 2 OUT
            bmAttributes            3
              Transfer Type            Interrupt
              Synch Type               None
              Usage Type               Data
            wMaxPacketSize     0x0010  1x 16 bytes
            bInterval              10
    Device Status:     0x0000
      (Bus Powered)

Answer 1

The javax.usb stuff can depend a lot on the flavor of linux you are running, and your machine's configuration in general.

You should try downloading and running the example programs, here on sourceforge , on your machine. If those do not work, then you should assume you'll need to change either the configuration of your machine, or something about your runtime.

I was having some problems with this library, and got the following recommendations . This information may be quite outdated, but it may help point you in the right direction:

Once downloaded and built, you need to ensure that libjusb.so gets copied over to $JAVA_HOME/jre/lib/i386, and that it has read and evecute permissions for your user. Also ensure that you have the usbdevfs virtual device mounted, and that your user has proper R/W access to it.

Lastly, depending on what USB device you want to talk to, you may need to disable hotplug (or at least blacklist any installed modules that may also attempt to talk to your device). If the device already has support in Linux, hotplug will load it's associated module and give it exclusive I/O access before you can grab the device from jUSB.

The above quoted text is from Brad Barclay. Hope this helps.