Thread: [pyusb-users] Error doing control transfer

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This is the complete log

Traceback (most recent call last):
>   File "myu.py", line 21, in <module>
>     dev.set_configuration()
>   File "C:\Python27\lib\site-packages\usb\core.py", line 547, in
> set_configuration
>     self._ctx.managed_set_configuration(self, configuration)
>   File "C:\Python27\lib\site-packages\usb\core.py", line 92, in
> managed_set_configuration
>     self.backend.set_configuration(self.handle, cfg.bConfigurationValue)
>   File "C:\Python27\lib\site-packages\usb\backend\libusb10.py", line 503,
> in set_configuration
>     _check(_lib.libusb_set_configuration(dev_handle, config_value))
>   File "C:\Python27\lib\site-packages\usb\backend\libusb10.py", line 403,
> in _check
>     raise USBError(_str_error[ret], ret, _libusb_errno[ret])
> usb.core.USBError: [Errno 2] Entity not found

My code is as follows

import usb.core
> import usb.util
> import sys
> # find our device
> dev = usb.core.find(idVendor=5824, idProduct=1503)
> # was it found?
> if dev is None:
>     raise ValueError('Device not found')
>
> print "VUSB Device Found" ## THE DEVICE GETS DETECTED
>

print dev.bNumConfigurations
> print dev.bDeviceClass
> print dev.bLength
>
> # set the active configuration. With no arguments, the first
> # configuration will be the active one
>
> dev.set_configuration()
> dev.ret = dev.ctrl_transfer(0xC0, 0x00, 0, 0, 128)

My OS is Windows 7 32-bit, using python 2.7.3 and pyusb-1.0.0a2
In above code the Device gets detected, but fails at the point where 'set
configuration' happens..

I tried equivalent code in C#(based on libUsbDotNet, which is also a
wrapper on libusb), and it worked fine.
Here is the c# code snippet for reference.

                MyUsbDevice = UsbDevice.OpenUsbDevice(MyUsbFinder);
>                 // If the device is open and ready
>                 if (MyUsbDevice == null) throw new Exception("Device Not
> Found.");
>                 // If this is a "whole" usb device (libusb-win32, linux
> libusb)
>                 // it will have an IUsbDevice interface. If not (WinUSB)
> the
>                 // variable will be null indicating this is an interface
> of a
>                 // device.
>                 IUsbDevice wholeUsbDevice = MyUsbDevice as IUsbDevice;
>
>                 if (!ReferenceEquals(wholeUsbDevice, null))
>                 {
>                     // This is a "whole" USB device. Before it can be
> used,
>                     // the desired configuration and interface must be
> selected.
>                     // Select config #1
>                     wholeUsbDevice.SetConfiguration(1);
>                     // Claim interface #0.
>                     wholeUsbDevice.ClaimInterface(0);
>                     Console.WriteLine("\r\nMAc MAc!\r\n");
>                 }
>
>                 UsbSetupPacket setup = new UsbSetupPacket(0xC0, 0x01, 0,
> 0, 128);
>                 bool result = MyUsbDevice.ControlTransfer(ref setup,
> buffer, 128, out ltt);
>                 Console.WriteLine("Result = {0}", result);

The only difference that I could find is that the c# code is doing
'CLAIM_INTERFACE', but that is done automatically by pyUsb.
Other thing that comes to my mind is the USB_BACKEND being in use by pyUsb.
I have not installed winUSB or OpenUSB. How do I check my currently active
USB backend.
what Is wrong with my python code?