Serial Port Problems

Archived from groups: microsoft.public.windowsxp.general (More info?)

I am having the following problem with my serial port (COM1), and it seems to
be windows (XP Professional) related:

I think Windows is controlling the DTR (pin4) and RTS (pin7) signals from
COM1. Instead of these pins being user controlable, windows seems to be
setting and holding them both active (+6V). On normal ports both signals are
negative (-5V). I think it is a Windows (and not hardware/bios) problem
because in bios mode (i.e. before windows boots up) both these pins are -5V,
however once windows starts up it controlls these pins makinging them +6V.
Curiously, when the computer wakes up from standby/hybernation both pins go
to -5V, however as soon as anything tries to access the port, both pins
return to +6V.

Has anyone else experianced this problem?? What is controlling these pins??
Is it a resource conflict?? How do i make XP Pro leave my serial port alone
to let other software control it??
This is driving me nuts, so all help/suggestions are greatly appreciated.

Thanks in advance,
Michael
--
Michael
2 answers Last reply
More about serial port problems
  1. Archived from groups: microsoft.public.windowsxp.general (More info?)

    > Has anyone else experianced this problem?? What is controlling these
    > pins??
    > Is it a resource conflict?? How do i make XP Pro leave my serial port
    > alone
    > to let other software control it??
    > This is driving me nuts, so all help/suggestions are greatly appreciated.


    Michael,

    Have you tried Jan Axelson's serial port website?
    http://www.lvr.com/serport.htm

    She has lots of excellent resources.

    Steve
  2. Archived from groups: microsoft.public.windowsxp.general (More info?)

    Please don't multi-post. See replies in hardware.

    Michael wrote:

    > I am having the following problem with my serial port (COM1), and it seems to
    > be windows (XP Professional) related:
    >
    > I think Windows is controlling the DTR (pin4) and RTS (pin7) signals from
    > COM1. Instead of these pins being user controlable, windows seems to be
    > setting and holding them both active (+6V). On normal ports both signals are
    > negative (-5V). I think it is a Windows (and not hardware/bios) problem
    > because in bios mode (i.e. before windows boots up) both these pins are -5V,
    > however once windows starts up it controlls these pins makinging them +6V.
    > Curiously, when the computer wakes up from standby/hybernation both pins go
    > to -5V, however as soon as anything tries to access the port, both pins
    > return to +6V.
    >
    > Has anyone else experianced this problem?? What is controlling these pins??
    > Is it a resource conflict?? How do i make XP Pro leave my serial port alone
    > to let other software control it??
    > This is driving me nuts, so all help/suggestions are greatly appreciated.
    >
    > Thanks in advance,
    > Michael
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