On 5/21/07, Karl Hiramoto <karl@hiramoto.org> wrote:

Mike Frysinger wrote:
> On 5/20/07, Stephen C. Daukas <scd@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