On 11/29/2010 3:25 PM John Smith said...

On 11/29/2010 4:20 PM, Emile van Sebille wrote:
On 11/29/2010 1:44 PM John Smith said...
But, when I tried it in Python, I got the same as before:

>>> import serial
>>> ser = serial.Serial(0, timeout = 1)

out of curiosity, if you change the timeout above to 5....

>>> ser
Serial<id=0x225c240, open=True>(port='COM1', baudrate=9600, bytesize=8,
parity='N', stopbits=1, timeout=1, xonxoff=False, rtscts=False,
>>> ser.read()

... does the delay before printing the traceback below take about 5

No. There is no delay regardless of the timeout setting.

>> Traceback (most recent call last):
>> File "<pyshell#3>", line 1, in <module>
>> ser.read()
>> File "E:\Python27\lib\site-packages\serial\serialwin32.py", line
>> 236, in read
>> raise SerialException("ReadFile failed (%s)" % ctypes.WinError())
>> SerialException: ReadFile failed ([Error 6] The handle is invalid.)
>>  >>>

Hmmm... any chance you don't have administrative rights on the account performing this? I never got to Win7 (having stopped at XP) but I know it's got a reputation for excessive permission asking.

Otherwise, I'd take this up on the main list. Chris Liechti, the [author|current maintainer|significant contributor] of pyserial monitors that list and would probably be interested in diagnosing what you're describing. You could also ask him as per the 'send me a message' link on his sourceforge page at



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