usb4java USB error 4: Unable to open USB device:

Question

I am attempting to interface with the PS3's DS3 controller. I have managed to do so in C# using an implementation of libusb but decided to move my implementation to java. Unfortunately my move to java has not been so smooth. The device seems to be found in the device list but when I attempt to open it I get the following error " USB error 4: Unable to open USB device: No such device (it may have been disconnected)"

public class Main {
private static final short VID = 0x054c;
private static final short PID = 0x0268;

Context context;

public Main() {
    context = new Context();
    int result = LibUsb.init(context);

    if (result != LibUsb.SUCCESS) {
        throw new LibUsbException("Unable to initialize libusb.", result);
    }

    ByteBuffer data = ByteBuffer.allocate(49);
    DeviceHandle ds3Handle = getDeviceHandle(findDevice(VID, PID));
    LibUsb.controlTransfer(ds3Handle, (byte)0xa1, (byte)0x1, (short)0x101, (short)0, data, 1000L);

    LibUsb.exit(context);
}

private Device findDevice(int vid, int pid) {
    Device UsbDevice = null;
    DeviceList list = new DeviceList();
    int result = LibUsb.getDeviceList(context, list);

    if (result < 0) {
        throw new LibUsbException("Unable to get device list", result);
    } 

    try {
        for(Device device: list) {
            DeviceDescriptor descriptor = new DeviceDescriptor();
            result = LibUsb.getDeviceDescriptor(device, descriptor);

            if (result != LibUsb.SUCCESS) {
                throw new LibUsbException("Unable to read device descriptor", result);
            } 

            if (descriptor.idVendor() == vid && descriptor.idProduct() == pid) {
                UsbDevice = device;
                System.out.println("found");
            }
        }
    } finally {
        LibUsb.freeDeviceList(list, true);
    }

    return UsbDevice;
}

private DeviceHandle getDeviceHandle(Device device) {
    DeviceHandle handle = new DeviceHandle();
    int result = LibUsb.open(device, handle);

    if (result != LibUsb.SUCCESS) {
        throw new LibUsbException("Unable to open USB device", result);
    }

    return handle;
}

public static void main(String [] args){
    new Main();
}
}

score 9 · Accepted Answer · answered Feb 26 '15 at 12:39

9

LibUsb.freeDeviceList(list, true);

That true is the problem. "final boolean unrefDevices" is shown in javadoc. Your code is releasing the Device before you have a chance to open it.

answered Feb 26 '15 at 12:39

Not Relevant

106
1
2

Can confirm, this is the solution to OP's problem. Just encountered the same issue using the same sample code from `usb4java`'s page. Much appreciated! – Matt Clark Mar 03 '15 at 05:21
Their website is on GitHub. Issued a PR. https://github.com/usb4java/usb4java.github.io/pull/2 – tresf Feb 29 '16 at 05:32
It seems that the error is indeed caused by the release of the devices, but how do I actually fix this? When I change my true into false, it gives another error. – Mathieu Brouwers Dec 13 '16 at 13:56

score 1 · Answer 2 · answered Aug 11 '17 at 15:17

Just changing to false it is not enough you also need to call refDevice with the device you need to return example:

    } finally {
        // Ensure the allocated device list is freed
        LibUsb.freeDeviceList(list, false);
    }

    if (deviceFound != null) {
        // Device found
        LibUsb.refDevice(deviceFound);
    }
    return deviceFound;

usb4java USB error 4: Unable to open USB device:

2 Answers2