[Wlug] Multiple RS232 Com Ports...

[Stephen Daukas]

On 5/21/07, Karl Hiramoto <karl at hiramoto.org> wrote:
>
> Mike Frysinger wrote:
> > On 5/20/07, Stephen C. Daukas <scd at daukas.com> wrote:
> >
> >>  I'm wondering if anyone knows how many RS232 devices a "vanilla" Linux
> >> kernel can manage simultaneously.
> >>
> >
> > there shouldnt be any real limit ... at work, we have ~24 USB<->RS232
> > devices hooked up and we use them all simultaneously to interact with
> > some hardware
> >
> >
> >> 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?
> >>
> >
> > i'd be more worried about *what* the devices are and *how* you connect
> > your 32 devices to the machine ... making sure linux has proper device
> > driver support for it
> > -mike


The *how* is the heart of my question...  If you mean how physically, that's
a matter of cable and such.
The driver question is, again, what I was looking into.  If Linux has
support for multiple RS232s built in
to one or more generic drivers in a given distro, then we are talking about
terminal emulation - a.k.a.
VT100 or ANSI or whatever.  Currently, the lab uses hyperterminal to talk
with the sondes - the sondes
are intelligent and provide a tty-based menu for command and control.  The
devices are known, so the
*what* isn't really an open question.

>
> Yes, there should be no real limit..  At work i have use multile
> Edgeport/8  http://www.digi.com/products/usb/edgeport.jsp   devices to
> have may rs-232 ports


How do the RS232 FIFO/Interrupts get managed via USB?  In other words, each
of the RS232s will need to have its "pin-outs" (DB-9) active so the sondes
believe they are connected in order to avoid their "turning off".  Also, is
it safe to assume the edgeport has its own drivers?

Regards,
Steve
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