[Oberon] monitoring an RS-232 interface.

eas-lab at absamail.co.za eas-lab at absamail.co.za
Wed Jun 18 16:56:42 CEST 2003

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'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.
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.
The serial port(s) only need attention when their FIFO (buffers)
are getting full or empty for Rx and Tx respectively.

Has n-o got the ability to interrupt for modem or mouse ?
I don't think so. Older machines had smaller buffered ser-chips
and would be more likely to 'overflow'. 

Normally, the ser-mouse and ser-modem ARE 'sharing' tasks.
Although not symetrically. From the papers which you kindly posted:
" Mouse and keyboard buffers are polled at each task switch in the 

The whole business of how (normally) the ser-modem is given and
releases its ser-port, is central to the ppp-bug which I'm 
investigating, and where readers 'look the other way' when
I ask questions. =:-(

> Is such a technique described elsewhere?  Any suggestions
> or improvements on my proposal?

There's a special name for this tool (which exists) that was 
mentioned in 2 of my threads in Newsgroups: comp.protocols.ppp.
Perhaps a google will lead to mention of how it works.
I think your idea is correct/do-able.
You could start (a-la Wirth) with a minimal system, by using your
modem port to monitor your mouse port.  This will prove to you 
if/how the basic concept is OK.

What is the serial port speed setting for the mouse ?

Chris Glur 

PS. keep me informed of progress please.

Thomas wrote:

> There is such a program for Aos/Bluebottle. You can link the watch 
> computer between
> the modem and the control computer. It usually works well as long 
> as the connection
> speed is not changed during the connection.
> I'll have to search for the program if you are interested.

Does it monitor both control computer AND modem.

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