title: NFCPY/libUSB crashing running examples
body: <p>I installed NFCPY, pyUSB and libusb on Mac Lion. I am using the common ACR122U NFC card reader and when I tried to run any of the examples it crashes. I know many people are using this same reader with NFCPY, I don't know why it doesn't work for me.</p>
  
  <p>Python doesn't print any error, however I can see this stack trace in the log file:</p>
  
  <pre><code>Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
  0   libusb-1.0.dylib                0x000000010f799bda darwin_reset_device + 10 (darwin_usb.c:1213)
  1   libffi.dylib                    0x00007fff87b2fe7c ffi_call_unix64 + 76
  2   libffi.dylib                    0x00007fff87b30ae9 ffi_call + 728
  3   _ctypes.so                      0x000000010f78033f _ctypes_callproc + 735
  4   _ctypes.so                      0x000000010f77afd2 0x10f777000 + 16338
  5   org.python.python               0x000000010f360d32 PyObject_Call + 97
  6   org.python.python               0x000000010f3e0f63 PyEval_EvalFrameEx + 14353
  7   org.python.python               0x000000010f3e3cd8 PyEval_EvalCodeEx + 1996
  8   org.python.python               0x000000010f381abf 0x10f359000 + 166591
  9   org.python.python               0x000000010f360d32 PyObject_Call + 97
  10  org.python.python               0x000000010f3e15ec PyEval_EvalFrameEx + 16026
  11  org.python.python               0x000000010f3e3cd8 PyEval_EvalCodeEx + 1996
  12  org.python.python               0x000000010f3e3e6c 0x10f359000 + 568940
  13  org.python.python               0x000000010f3e0e0a PyEval_EvalFrameEx + 14008
  14  org.python.python               0x000000010f3e3df7 0x10f359000 + 568823
  15  org.python.python               0x000000010f3e0e0a PyEval_EvalFrameEx + 14008
  16  org.python.python               0x000000010f3e3df7 0x10f359000 + 568823
  17  org.python.python               0x000000010f3e0e0a PyEval_EvalFrameEx + 14008
  18  org.python.python               0x000000010f3e3cd8 PyEval_EvalCodeEx + 1996
  19  org.python.python               0x000000010f381abf 0x10f359000 + 166591
  20  org.python.python               0x000000010f360d32 PyObject_Call + 97
  21  org.python.python               0x000000010f36f6e9 0x10f359000 + 91881
  22  org.python.python               0x000000010f360d32 PyObject_Call + 97
  23  org.python.python               0x000000010f3ab484 0x10f359000 + 337028
  24  org.python.python               0x000000010f3a5b7a 0x10f359000 + 314234
  25  org.python.python               0x000000010f360d32 PyObject_Call + 97
  26  org.python.python               0x000000010f3e0f63 PyEval_EvalFrameEx + 14353
  27  org.python.python               0x000000010f3e3df7 0x10f359000 + 568823
  28  org.python.python               0x000000010f3e0e0a PyEval_EvalFrameEx + 14008
  29  org.python.python               0x000000010f3e3cd8 PyEval_EvalCodeEx + 1996
  30  org.python.python               0x000000010f3e3e6c 0x10f359000 + 568940
  31  org.python.python               0x000000010f3e0e0a PyEval_EvalFrameEx + 14008
  32  org.python.python               0x000000010f3e3cd8 PyEval_EvalCodeEx + 1996
  33  org.python.python               0x000000010f381abf 0x10f359000 + 166591
  34  org.python.python               0x000000010f360d32 PyObject_Call + 97
  35  org.python.python               0x000000010f36f6e9 0x10f359000 + 91881
  36  org.python.python               0x000000010f360d32 PyObject_Call + 97
  37  org.python.python               0x000000010f3ab484 0x10f359000 + 337028
  38  org.python.python               0x000000010f3a5b7a 0x10f359000 + 314234
  39  org.python.python               0x000000010f360d32 PyObject_Call + 97
  40  org.python.python               0x000000010f3e0f63 PyEval_EvalFrameEx + 14353
  41  org.python.python               0x000000010f3e3df7 0x10f359000 + 568823
  42  org.python.python               0x000000010f3e0e0a PyEval_EvalFrameEx + 14008
  43  org.python.python               0x000000010f3e3cd8 PyEval_EvalCodeEx + 1996
  44  org.python.python               0x000000010f3e3d4d PyEval_EvalCode + 54
  45  org.python.python               0x000000010f3fb08f 0x10f359000 + 663695
  46  org.python.python               0x000000010f3fb14f PyRun_FileExFlags + 157
  47  org.python.python               0x000000010f3fc2a2 PyRun_SimpleFileExFlags + 392
  48  org.python.python               0x000000010f40c2af Py_Main + 2715
  49  org.python.python               0x000000010f34ee88 0x10f34e000 + 3720
  
  Thread 1:: org.libusb.device-detach
  0   libsystem_kernel.dylib          0x00007fff90e2967a mach_msg_trap + 10
  1   libsystem_kernel.dylib          0x00007fff90e28d71 mach_msg + 73
  2   com.apple.CoreFoundation        0x00007fff90082b6c __CFRunLoopServiceMachPort + 188
  3   com.apple.CoreFoundation        0x00007fff9008b2d4 __CFRunLoopRun + 1204
  4   com.apple.CoreFoundation        0x00007fff9008aae6 CFRunLoopRunSpecific + 230
  5   com.apple.CoreFoundation        0x00007fff9009a7ff CFRunLoopRun + 95
  6   libusb-1.0.dylib                0x000000010f79e997 event_thread_main + 631 (darwin_usb.c:369)
  7   libsystem_c.dylib               0x00007fff903888bf _pthread_start + 335
  8   libsystem_c.dylib               0x00007fff9038bb75 thread_start + 13
  
  Thread 2:: Dispatch queue: com.apple.libdispatch-manager
  0   libsystem_kernel.dylib          0x00007fff90e2b7e6 kevent + 10
  1   libdispatch.dylib               0x00007fff92d9e5be _dispatch_mgr_invoke + 923
  2   libdispatch.dylib               0x00007fff92d9d14e _dispatch_mgr_thread + 54
  
  Thread 3:
  0   libsystem_kernel.dylib          0x00007fff90e2b192 __workq_kernreturn + 10
  1   libsystem_c.dylib               0x00007fff9038a594 _pthread_wqthread + 758
  2   libsystem_c.dylib               0x00007fff9038bb85 start_wqthread + 13
  
  Thread 0 crashed with X86 Thread State (64-bit):
    rax: 0x000000010f7a2320  rbx: 0x0000000000000000  rcx: 0x000000010f985f80  rdx: 0x0000000000000000
    rdi: 0x0000000000000000  rsi: 0x0000000000000001  rbp: 0x00007fff6ef4baa0  rsp: 0x00007fff6ef4ba90
     r8: 0x000000010f48e840   r9: 0x0000000000000000  r10: 0x00007fff6ef4ba00  r11: 0x000000010f795340
    r12: 0xffffffffffffffff  r13: 0x0000000000000001  r14: 0x0000000000000000  r15: 0x00007fff6ef4bab0
    rip: 0x000000010f799bda  rfl: 0x0000000000010246  cr2: 0x0000000000000058
  Logical CPU: 1
  </code></pre>
  
  <p>Any help would be very appreciated, I am stuck with this for many days</p>