[Oberon] monitoring an RS-232 interface.

mcintosh at vima.austin.tx.us mcintosh at vima.austin.tx.us
Sun Jul 27 20:04:55 CEST 2003

Back in 18 Jun 2003 16:56:42 +0200 (MEST) Chris Glur <eas-lab at absamail.co.za> wrote:

> peter_easthope wrote:
> > Here is a rather unusual problem.
> Answers to my NewsGroup queries described such a device as 
> being essential. It's a worth while project.
> > I want to monitor the serial interface
> > of an external modem.  The approach I am 
> > considering is a generalization of that 
> > described in 
> > "http://www.oberon.ethz.ch/native/WebTrace.html" .


I have made a prototype PCB that should be helpful for this project.  An 
ongoing discussion on this may be found in sci.electronics.design through 
Google newsgroups looking for "Aubrey" "RS232".

I have received a prototype board from Olimex, stuffed it with parts, and 
tested it, as documented in s.e.d.

I have breadboarded the next phase of the design onto the prototype PCB.  
I have modified the schematic and PCB layout files to reflect this second 
design.  However, the second design has not been sent to Olimex, and so 
the second CAD/CAM files are not fully tested.  They are, however, ready 
to zip and submit.

The CadSoft EAGLE and Adobe Acrobat files are located at:


I am willing to share my PCB design with the Oberon community for non profit 
use.  Please feel free to download the design and use it.  I retain the 
copyright and rights.  If you need Gerber files or have other questions,
let me know.


The board is outfitted with a DCE and DTE connector for RS-232.  It plugs 
into an existing serial circuit, such as that between a computer and a modem.  
When supplied with Gnd and +5 V, and is not otherwise controlled, it is 
'transparant.'  That is, the circuit continues to work as if the board 
were not there.  The board requires clean +5V, as it does not have on-board
regulators and the like.

The 8 primary RS-232 signals are level converted from +-20V to 0-5V and 
brought to a 0.100" socket on the board.  The RS-232 traffic in both 
directions may be passively monitored.  The handshake lines, a source of 
troubleshooting interest, may be monitored.

RS-232 has a secondary data channel as well.  This is complimentary to 
RD and TD on pins 2, 3, and is called STD and SRD on pins 14, 16.  These 
4 pins are supported by this board as well.  These 4 signals (STD, SRD, 2 
connectors) are also available as 0-5V I/O lines on the socket.


I have opened two V24 panels in ETH Oberon running under Windows 2000.  
I opened COM1 on 1 panel, and COM2 on the other panel.  I connected a 
Motorola Evaluation board through my RS-232 Explorer board, and a serial
camera cable to the other COM port to the (breadboarded) board.  I jumpered
the output socket for the test.  I am able to interact with the board 
through 1 V24 panel, and the Motorola board through the other V24 panel.

This was not a speed stress test.


I have corresponded with the editor of "Nuts and Volts" magazine, and I have
an expression of interest in publishing an article on the RS-232 
explorer + controller project.

There are additional issues in trying to debug PPP over RS-232.  I have 
also designed a controller board to work with the socket on the explorer
board.  The characters going in each direction need to be timestamped, 
there may be a desire to interact with the RS-232 traffic.   There may
even be a need to supply or correct the handshake lines.

At a minimum, the controller board can display the traffic in each direction
as a pattern of lights on an LED.  It can display the status of the various
control lines on the LEDs.  It can test for the integrity of frames in the
PPP packets, and send diagnostic and summary information out the secondary
data channel.

With a binary protocol on the secondary data channel, it is possible to 
display the direction and time of each packet in a color coded Oberon viewer.

I believe that another article, by another author, that uses a different CPU
than the PIC 16F877 that I have chosen, or one that investigates another 
application (I am not diagnosing PPP, only providing an Explorer system) would
have a significant chance of publication.  I believe that such a series of
publications in Nuts and Volts would greatly enhance the visibility of Oberon,
and put some cash into the author's hobby.

G.R. produced a Motorola 68HC11 compiler for Oberon that I am using.  There 
is a 68000 compiler, but I can't produce a board physically big enough 
for a 68000.  There may be other microcomputer compilers for Oberon as 
well.  If so, I would like to hear of them.  It is at least possible 
to use the 68HC11 as the controller and also work in Oberon.


>  I've archived this. It's only about 10 lines. Is that right ?
>  "WebTrace" seems to be a poorly chosen name.
> > In this case we need to monitor both sending and 
> > receiving lines.  This will require a tee serial cable with 
> > the side branch dividing to two cables.  One of these 
> > side branches needs the send and receive lines 
> > crossed.  This special cable will be inserted between 
> > the modem and the server.  Then one "observer" 
> > machine can be attached to each of the side branches.
> > 
> Yes: 
> Tx ser-port = Rx modem --> Rx monitor 1
> Rx ser-port = Tx modem --> Rx monitor 2
> > WIth this setup, one observer will monitor transmissions 
> > from computer to modem and the other will monitor 
> > transmissions from modem to computer.  Perhaps one 
> > machine with two serial ports is capable of monitoring 
> > both lines.  No doubt this would work with Unix but I 
> > have not tried running two concurrent V24 tasks in Oberon.
> > 
> What is the serial port speed setting for the mouse ?

Aubrey McIntosh, Ph.D.
1502 Devon Circle
Austin TX 78723-1814

ETH PlugIn Oberon for WindowsTM / Win32 2.4 (15.12.2000)
	 on Windows 2000 Version 5.0.2195  mcintosh at DELTA

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