home *** CD-ROM | disk | FTP | other *** search
- Path: sparky!uunet!mcsun!uknet!glasgow!gjw
- From: gjw@dcs.glasgow.ac.uk (Mr Garry J. Wardrope)
- Newsgroups: sci.electronics
- Subject: Re: RS-232 Line Monitor???
- Message-ID: <Btzut1.DtM@dcs.glasgow.ac.uk>
- Date: 3 Sep 92 08:41:24 GMT
- References: <geb1.715477196@Isis.MsState.Edu>
- Organization: Glasgow University Computing Science Dept.
- Lines: 44
-
- geb1@ra.msstate.edu (Granville Barker) writes:
-
- >I am trying to build a RS-232 line monitor.
-
- >I want to connect it between two RS-232 devices, and have a wire comming
- >off that I can connect to another computer and monitor both sides of the
- >conversation between the other two devices. Ie.. a Plotter and a Computer.
-
- >I need to see what is being transmited and received, I tried hooking
- > pins 2 and 3 to diodes, then connecting rx on the monitor computer to
- > the other end of the diodes. THe other 2 devices still communicate ok, but
- > I never see anything on my monitor computer. I am connecting ground.
-
- > Any ideas??
-
-
- >Thanks,
-
- >Granville Barker
- >geb1@isis.msstate.edu
-
-
- I'm not surprised it dosn't work. First of all RS232 signals are not 0v and
- some +ve voltage. A 1 is -5 to15v and 0 is +5 to 15v ( I think I've got this
- the right way round). 0v (-5 to +5) is indetermiate so strictly using diodes
- to mix the signals shouldn't work. It does work with some machines though as in real life an indterminate state has to be something.
-
- Second if both machines talk at the same time then the mixed signal will be
- garbage, this setup will only work in half-duplex mode. ( or simplex)
-
- You would have to use 2 serial ports to monitor 2 way conversations (and to
- be able to tell where the data was comeing from).
-
- Chances are you only want to use this set up to occasionally check systems.
- It would probably be easier to monitor each device seperatly - sending the same data.
-
- Hope this is of some help
- Garry
-
- --
- Mail: Garry Wardrope, Computing Science Dept., Tel: (041) 339 8855 x5322
- Glasgow Univ., 17 Lilybank Gardens, Glasgow G12 8QQ, UK.
- email: gjw@dcs.glasgow.ac.uk
- ".. and even if I came in sight of paradise what price its moon without Marsco"
-