Re: OT: Windows serial port sniffing

Top Page
This message is part of the following thread:
Mthe complete thread tree sorted by date
Mkoder at <-
M 
Attachments:
Message as email
+ (text/plain)
+ (text/html)
+ (text/plain)
Delete this message
Reply to this message
Author: Eric Cope
Date:  
To: iscreamkid, Main PLUG discussion list
Subject: Re: OT: Windows serial port sniffing
You may want to increase those resistors by an order of magnitude to reduce
current drain requirements. Some serial cards may not like providing 1mA of
constant dc current.

Eric

On Mon, Aug 18, 2008 at 2:40 PM, koder <> wrote:

> Sorry for the delay, but I had a meeting to attend.
>
> Eric is absolutely correct about the need for a voltage divider.
> You will need to determine that the output of your system is not ging to
> overwhelm things.
>
> The article I had in mind is calling for an 1/11 divider.
>
> Electronic Circuits for the Evil Genius by Dave Cutcher
>
> http://www.books.mcgraw-hill.com/authors/cutcher
>
>
> There you will find the Windoze program Winscope 2.51
>
> The black wire will go from your ground to the base portion of the audio
> plug. Use a 100 ohm resister to bridge the black wire to the red wire which
> goes to the tip.
>
> >From the junction of the red wire and the 10 ohm resister connect a 1000
> ohm resister. The other end of the resister goes to your connection.
>
> I accept no responsibility for any damage to equipment for any
> miscommunication regarding the construction of this circuit.
>
> Cutcher says your sound card will not take more than two volts.
> The divider will drop a nine volt signal to .8 volts.
>
> I no longer have a Win machine so I have not been able to use this circuit.
> I hope someday to write such a program in Linux, but if someone else gets
> there first it will not break my heart
>
> Harold
>
> -----Original Message-----
> *From*: Eric Cope <<%3e>
> >
> *Reply-To*: Main PLUG discussion list <
> <%3e>
> >
> *To*: , Main PLUG discussion list <
> <%3e>
> >
> *Subject*: Re: OT: Windows serial port sniffing
> *Date*: Mon, 18 Aug 2008 10:50:02 -0700
>
> be careful at connecting serial wires +-15v to audio inputs... Unless you
> know what a voltage divider is...
> A divide by 10 sounds correct, but I am not sure...
> http://www.physicsforums.com/showthread.php?t=131827
>
> I recall being able to control some of the handshake wires in a serial
> connection in a windows program in a manner that you describe, but that was
> a few years ago... There should be some tutorials on Google...
>
> http://msdn.microsoft.com/en-us/library/ms810467.aspx
>
> Good luck,
> Eric
>
> On Mon, Aug 18, 2008 at 10:39 AM, koder <> wrote:
>
> There is a program which I am pretty sure is free that will look at the
> voltage levels on the serial port and display them as a graphic display.
> it was intended to allow you to use the serial port as a voltmeter.
>
> The program is made available by the man who writes the Evil Genius
> series of hardware books.
>
> I am not able to give more information at this time.
>
> What you do is run a wire across a resister that drops the voltage to
> audio levels. Plug the wire into the line in on your sound card. The
> program seed the analog signal and displays it on the graph.
>
> Harold
>
>
>
> -----Original Message-----
> From: Charles Jones <>
> Reply-To: Main PLUG discussion list
> <>
> To: plu >> Main PLUG discussion list
> <>
> Subject: OT: Windows serial port sniffing
> Date: Mon, 18 Aug 2008 08:46:49 -0700
>
> This is technically a windows question, but I thought I would ask here
> anyway, because many of us were hacking before MS-windows existed, and
> also ran various versions of MS-windows in our time (which is why we
> love Linux so much now!) and have dealt with serial ports from dealing
> with modems and the like. I figured I would tell you all about a minor
> problem I am thinking of tackling, and see if you had any suggestions.
>
> I'm dealing with an RFID badge-access system that uses windows-based
> administration software. Basically some software that runs on windows,
> using an mssql db, and communicates with the hardware via the serial port.
>
> The software has a function to send a timed pulse to unlock a door(s)
> for X number of seconds. I'm looking for a way to do the same thing,
> but from another machine so that I can use a script or even a CGI to
> control the door. Yes, I realize this opens us up to someone "hacking"
> their way into the office, but we also have a security system and if
> they have root on our servers then we have bigger problems :) I digress...
>
> I have some long ago experience in serial port programming. In school I
> wrote a voicemail system in Turbo Pascal (heh), that controlled a POTS
> line via a relay that I connected to the serial port. I remember
> studying the serial port pinouts and figuring out how to control the
> voltage level to each of the pins.
>
> That being said, I have several things I have to consider:
> * Is the door lock pulse simply a voltage level sent to the serial port,
> or is there some sort of protocol (an actual serial connection) between
> the computer and the hardware?
> * Is the signal being sent just a toggle, or a specific turn on/off events?
>
> I basically need a way to snoop the serial port to see what is being
> sent, but I'm not sure of the best way to do it. If it is just voltage
> levels being sent to the hardware, I could do it with just a multimeter
> and figure out which pins it is activating. However, if there is an
> actual serial connection (null modem or something) going on, it will be
> much more difficult to observe what data is being sent. I think also you
> can purchase an in-line dongle that has LEDs that will show the status
> of the data lines.
>
> I suppose one of the first things I could do is to just unplug the
> serial port, and try to use any functions that talk to the hardware. If
> there is any data connection required, it should complain that it is not
> connected.
>
> Theoretically I could write a small a small C++, (or even Win32 perl)
> daemon that would run on the winblows machine and provide a way to
> toggle the lock/unlock signal via a TCPIP connection. I may run into a
> snag where, if I remember correctly, if something has control of a
> serial port in Windows, no other process can open it. Maybe I could do
> something sneaky like a Y-adapter and just send the signal from another
> machine altogether. I wonder if I would have to use some diodes to keep
> any voltage from one leg of the Y from traveling back to the other
> machines serial port...hmmm
> ---------------------------------------------------
> PLUG-discuss mailing list -
> To subscribe, unsubscribe, or to change your mail settings:
> http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss
>
> ---------------------------------------------------
> PLUG-discuss mailing list -
> To subscribe, unsubscribe, or to change your mail settings:
> http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss
>
>
>
> ---------------------------------------------------
> PLUG-discuss mailing list -
> To subscribe, unsubscribe, or to change your mail settings:http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss
>
>
> ---------------------------------------------------
> PLUG-discuss mailing list -
> To subscribe, unsubscribe, or to change your mail settings:
> http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss
>
---------------------------------------------------
PLUG-discuss mailing list -
To subscribe, unsubscribe, or to change your mail settings:
http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss
This message was posted to the following mailing lists:
Plug Discuss
Mailing List Info | Nearby Messages		<-Re: OT: Windows serial port sniffingLooking for ways to limit access to a Windows Program->
Some Mailing List Archive administrated by UnconfiguredLurker (version 2.3)