Re: WaitCommEvent questions

"Igor Tandetnik" <>
Sun, 13 Jan 2008 13:20:00 -0500
"Dave Cullen" <> wrote in message

Does WaitCommEvent only trigger when the control lines change in one
direction, or both directions?

It triggers whenever the value of the line changes from 0 to 1 or from 1
to 0, as far as I know.

I need to count pulses comming in on comport control lines DSR and
CTS. If the event triggers in either direction then I need a way to
determine if the line is "1" or "0". Is there a function to read
their current value?


Also, does WaitCommEvent time out if no change happens or will it hang
forever waiting for a change?

It doesn't support a timeout. But you can open a file in overlapped mode
and have WaitCommEvent run asynchronously. Then you can cancel it with
With best wishes,
    Igor Tandetnik

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