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Re: [pyusb-users] Error doing control transfer
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From: Wander L. C. <wan...@gm...> - 2013-10-02 14:02:19
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2013/10/2 vvyogi . <vv...@gm...>
>
> I installed pyUsb from the the master branch (github), and I wrote the following code
>>
>>
>> import usb.core
>> import usb.util
>> import sys
>> import os
>> # find our device
>> os.environ['PYUSB_DEBUG_LEVEL'] = 'debug' # IS THIS RIGHT WAY TO DO THE ENVIRONMENT VARIABLES
>> os.environ['PYUSB_DEBUG'] = 'debug'
>>
You have to setup environment variables before importing usb stuff.
That's because you aren't getting any log.
>> dev = usb.core.find(idVendor=5824, idProduct=1503)
>> # was it found?
>> if dev is None:
>> raise ValueError('Device not found')
>>
>> print "VUSB Device Found"
>> 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)
>
>
> This is the output:
>>
>> VUSB Device Found
>> 1
>> 255
>> 18
>>
>> Traceback (most recent call last):
>> File "myu.py", line 24, in <module>
>> dev.set_configuration()
>> File "C:\Python27\lib\site-packages\usb\core.py", line 559, 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\libusb1.py", line 741, in set_configuration
>> _check(self.lib.libusb_set_configuration(dev_handle.handle, config_value))
>> File "C:\Python27\lib\site-packages\usb\backend\libusb1.py", line 571, in _check
>>
>> raise USBError(_str_error[ret], ret, _libusb_errno[ret])
>> usb.core.USBError: [Errno 2] Entity not found
>
>
> It seems almost same to the previous log.
> As for the libUsbDotNet, I don't know how do I figure out its back-end. I ran a libUsbtest application that came with LibUSB-Win32 and Its snapshot is attached.
>
>
>
> Thanks and Regards
> Vivek
>
> On Wed, Oct 2, 2013 at 5:45 PM, Wander Lairson Costa <wan...@gm...> wrote:
>>
>> 2013/10/2 vvyogi . <vv...@gm...>:
>> > 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
>> >
>>
>> set_configuration is faling here, but this you probably already know...
>>
>> >
>> > 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)
>> >
>>
>> Your code looks fine, at least until the set_configuration call.
>>
>> >
>> >
>> > 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..
>> >
>>
>> What about latest pyusb code from github?
>>
>> > 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?
>> >
>>
>> Your PyUSB backend is libusb 1.0, libusbdotnet can use libusb-win32,
>> WinUSB or libusb 1.0. AFAIK, libusb 1.0 production code can only use
>> WinUSB right now.
>> Do you know what backend is being used by libusbdotnet?
>>
>> Let's try to see what PyUSB is doing. Please, define the environment
>> variable PYUSB_DEBUG_LEVEL=debug (for a2 release) or PYUSB_DEBUG=debug
>> (for github HEAD), run your program again and post here the logs.
>>
>>
>> --
>> Best Regards,
>> Wander Lairson Costa
>>
>> ------------------------------------------------------------------------------
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>> _______________________________________________
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>
>
>
> ------------------------------------------------------------------------------
> October Webinars: Code for Performance
> Free Intel webinars can help you accelerate application performance.
> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from
> the latest Intel processors and coprocessors. See abstracts and register >
> http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk
> _______________________________________________
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> pyu...@li...
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>
--
Best Regards,
Wander Lairson Costa
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