Question

I have usb mass stroage with led

I am trying to light on and off the led

using usb packet sniffing tool USBlyzer,

I can get the raw data

55 53 42 43 58 66 93 88 00 00 00 00 00 00 06 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

whose Request info is Bulk or Interrupt Transfer and I/O is out

and in the USB properties section

I can get the info such as

Endpoint Descriptor 81 1 In, bulk, 512 bytes

bDescriptorType 05h Endpoint

bEndpointAddress 81h 1 In

Endpoint Descriptor 02 2 In, bulk, 512 bytes

bDescriptorType 05h Endpoint

bEndpointAddress 02h 2 Out

I made a python code with python 2.7, libusb-win32-bin-1.2.4.0, pyusb-1.0.0-a1

the full source is here

import usb.core
import usb.util

# find our device
dev = usb.core.find(idVendor=0x1516, idProduct=0x8628)

# was it found?
if dev is None:
    raise ValueError('Device not found')

dev.set_configuration()
# get an endpoint instance
cfg = dev.get_active_configuration()
interface_number = cfg[0].bInterfaceNumber
alternate_setting = usb.control.get_interface(interface_number)
intf = usb.util.find_descriptor(cfg, bInterfaceNumber = \
                                ineterface_number, bAlternateSetting = alternate_setting)
ep = usb.util.find_descriptor(intf,custom_match = \
                                  lambda e: \
                                      usb.util.endpoint_direction(e.bEndpointAddress) == \
                                      usb.util.ENDPOINT_OUT)
# set the active configuration. With no arguments, the first
# configuration will be the active one


assert ep is not None

ep.write(0x2,0x55)
ep.write(0x2,0x53)
ep.write(0x2,0x42)
ep.write(0x2,0x43)
ep.write(0x2,0x58)
ep.write(0x2,0x66)
ep.write(0x2,0x93)
ep.write(0x2,0x88)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x06)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)
ep.write(0x2,0x00)

but when I try to execute it,

Traceback (most recent call last):
  File "C:\Documents and Settings\kty1104\Desktop\usb2.py", line 14, in <module>
    interface_number = cfg[0].bInterfaceNumber
  File "C:\Python27\lib\site-packages\usb\core.py", line 447, in __getitem__
    return Interface(self.device, index[0], index[1], self.index)
TypeError: 'int' object is not subscriptable

arise

what’s wrong with my code?

any if anything wrong concept is there, please let me know

thanks!

Answer 1

I don’t know anything about pyusb, but my interpretation of the error message is that, contra others’ opinions, cfg is not an integer, but that it requires a non-integral index. I say this because the exception is thrown in a __getitem__ function, which could only be cfg‘s __getitem__, because that’s the only place a __getitem__ call would be made in the line

interface_number = cfg[0].bInterfaceNumber

Now if cfg were an int, it wouldn’t have a __getitem__. The problem is that cfg‘s __getitem__ seems to expect to be able to subscript the index that it receives, as illustrated by the middle two arguments, index[0], index[1]. Since you passed cfg an integer, that’s impossible.

---

From the tutorial:

You can also use the subscript
operator to access the descriptors
randomly, like that:

>>> # access the second configuration
>>> cfg = dev[1]
>>> # access the first interface
>>> intf = cfg[(0,0)]
>>> # third endpoint
>>> ep = intf[2] 

As you can see, the index is zero based. But wait! There
is something weird in the way I access
an interface… Yes, you are right,
the subscript operator in the
Configuration accepts a sequence of
two items, with the first one being
the index of the Interface and the
second one, the alternate setting. So,
to access the first interface, but its
second alternate setting, we write
cfg[(0,1)].