[Wlug] Multiple RS232 Com Ports...

Stephen C. Daukas scd at daukas.com
Sun May 20 12:19:54 EDT 2007

Hi all!

I'm wondering if anyone knows how many RS232 devices a "vanilla" Linux 
kernel can manage simultaneously.  I'd like to be able to have up to 32 
going at once, with data taken from each device written to its own file 
via the standard I/O subsystem.  As far as I know, wouldn't Linux simply 
fork the appropriate number of driver threads to read as many RS232 
ports as are attached with each device's stream written to a "/dev" file?

Why do I want to do this?  Glad you asked...

I'm investigating an issue at work that involves our instrumentation lab 
having to upload/download/calibrate multiple sondes and have them ready 
for field deployment the next day.  Currently, we can do three at a time 
and this takes about 8-9 hours providing everything goes well. 

The manufacturer's software application claims to supports the 
simultaneous upload/config of up to 32 sondes.  The application will 
scan "installed" COM ports looking for recognizable sondes, and present 
those found to the user. Yes - this is a windows solution, so I first 
began looking for products that would play with Windows...

I began looking for hardware solutions (PCI boards, break-out boxes, 
etc.) on the net and I found a few that will provide 16 DB-9 RS232 ports 
with full pin-out support as well as so-called "true" interrupt and FIFO 
support on the host (via their own custom Windows driver, no doubt).  
And then I started wondering about how to get all of this to work in a 
Windows environment where "IT" is the only group allowed to install 
software and otherwise configure a PC for most users whose biggest 
concern is email...

All this got me thinking about avoiding the whole Windows issue and 
instead thinking about using Linux to take care of the RS232 part, with 
the newly created files moved to a Windows box (sneakernet to start 
with), with the normal post-processing of the data taking place as usual 
in the Windows environment the staff is used to...

I'm hoping an "out of the box" distro will be able to handle say 16 
RS232 ports and that Linux-based terminal emulation software is 
available to simultaneously handle those ports as well so I can capture 
the data using the appropriate protocols...  Anyone know of a similar 
application using RS232 and Linux, or have some thoughts on this?

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