Python 2.7 使用XBee 2.1.0的随机异常

我有一个运行python应用程序的raspberry pi，它只是发送一个数据包并等待响应。问题是，我随机得到以下异常：

    Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 552, in __bootstrap_inner
    self.run()
  File "/usr/local/lib/python2.7/dist-packages/xbee/base.py", line 95, in run
    self._callback(self.wait_read_frame())
  File "/usr/local/lib/python2.7/dist-packages/xbee/base.py", line 399, in wait_read_frame
    frame = self._wait_for_frame()
  File "/usr/local/lib/python2.7/dist-packages/xbee/base.py", line 131, in _wait_for_frame
    byte = self.serial.read()
  File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 456, in read
    raise SerialException('device reports readiness to read but returned no data (device disconnected?)')
SerialException: device reports readiness to read but returned no data (device disconnected?)

有人知道这是为什么吗？和你知道我能做些什么来修复它吗？我试着用Try:Except，但没用

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非常感谢

过了一会儿，我才发现问题出现了，因为我的XBee是通过USB连接的。我直接将它改为串行，它已经运行了几个月没有任何问题