new_contents: #!/usr/bin/python -u
  """
  test serial loopback; assumes Rx and Tx are connected
  
  Copyright (c) 2010-2013 Ben Bass <benbass@codedstructure.net>
  All rights reserved.
  """
  
  import os
  import sys
  import time
  
  from pylibftdi import Device
  
  
  def test_string(length):
      return os.urandom(length)
  
  
  class LoopbackTester(object):
      def __init__(self):
          self.device = Device()
  
      def test_loopback(self, lengths):
          self.device.flush()
          time.sleep(0.1)
          for l in lengths:
              test_str = test_string(l)
              self.device.write(test_str)
              time.sleep(0.1)
              result = ''
              for _ in range(3):
                  result = self.device.read(l)
                  if result:
                      break
              if result != test_str:
                  self.device.flush()
                  time.sleep(0.25)
              yield result == test_str
  
      def main(self):
          for bd in [9600, 115200, 1152000]:
              self.device.baudrate = bd
  
              for result in self.test_loopback(range(1, 50) +
                                               range(1000, 5000, 1000)):
                  if result:
                      sys.stdout.write('+')
                  else:
                      sys.stdout.write('!')
              sys.stdout.write('\n')
  
  
  if __name__ == '__main__':
      tester = LoopbackTester()
      tester.main()
  
subject: add serial_loopback example