WaitCommEvent error

[jim]

Hi, All
I am using python (activestate 2.2.2-224) on XP home and have suddenly got
the
following error from a file which worked fine under millenium.

self.Overlapped = win32file.OVERLAPPED()
self.overlapped.hEvent = CreateEvent(None, 0, 0, None)

hComm = win32file.CreateFile(comport,
          win32con.GENERIC_READ | win32con.GENERIC_WRITE,
          0,
          None,
          win32con.OPEN_EXISTING,
          win32con.FILE_ATTRIBUTE_NORMAL | win32con.FILE_FLAG_OVERLAPPED,
          None)

Error -

 File "E:\code\Python\PyModbus\FEModbusV101.py", line 162, in ComPortWrite
    rc,mask =win32file.WaitCommEvent(self.hComm,self.Overlapped)
api_error: (87, 'WaitCommError', 'The parameter is incorrect.')


I think the api call requires 3 parameters but only 2 are used in python any
ideas ?

many thanks
 Jim