树莓派用python控制串口的问题

开始没问题，隔段时间就会出这个错误，貌似是缓存区的问题。
Traceback (most recent call last):
File "/home/pi/tty.py", line 18, in <module>
count = ser.inWaiting()
File "/usr/lib/python2.7/dist-packages/serial/serialutil.py", line 572, in inWaiting
return self.in_waiting
File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 456, in in_waiting
s = fcntl.ioctl(self.fd, TIOCINQ, TIOCM_zero_str)
IOError: [Errno 5] Input/output error