I'm having a bit of difficulty reading from my device.. It seems that I have to 
make the Device.read() call multiple times in order to get the response.  I 
wrote a short test code that inserts a variable delay between reads.  
Regardless of the delay value it seems to always take 3 or 4 read() calls 
before I get my response.  Please see below.  d is an instance of 
usb.core.Device.

any ideas why this is happening??? 

Python 3.4.0 (default, Apr 11 2014, 13:05:11) 
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IPython 1.2.1 -- An enhanced Interactive Python.
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could not detach kernel driver index 1
could not detach kernel driver index 2

In [1]: speedtest??
Type:       function
String Form:<function speedtest at 0x7ffba6f6e048>
File:       /home/walker/software/stopsen/testing/py_usb.py
Definition: speedtest(d, delay=0.1)
Source:
def speedtest( d, delay = 0.1 ):
  d.write(2, 'a')
  for i in range(5):
    time.sleep(delay)
    print("{0}: {1}".format(i + 1, "".join(chr(a) for a in d.read(0x81, 20))))

In [2]: speedtest( d, .2 )
1: 
2: 
3: 
4: 1403-OS4X-0303-0008

5: 

In [3]: speedtest( d, .1 )
1: 
2: 
3: 
4: 1403-OS4X-0303-0008

5: 

In [4]: speedtest( d, 1 )
1: 
2: 
3: 
4: 1403-OS4X-0303-0008

5: 

In [5]: speedtest( d, 2 )
1: 
2: 
3: 
4: 1403-OS4X-0303-0008

5: 

In [6]: 

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