[Wlug] Multiple RS232 Com Ports...
karl at hiramoto.org
Mon May 21 09:31:43 EDT 2007
Stephen Daukas wrote:
> On 5/21/07, *Karl Hiramoto* <karl at hiramoto.org
> <mailto:karl at hiramoto.org>> wrote:
> Mike Frysinger wrote:
> > On 5/20/07, Stephen C. Daukas <scd at daukas.com
> <mailto: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
> > devices hooked up and we use them all simultaneously to interact
> > 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
> > your 32 devices to the machine ... making sure linux has proper
> > 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?
Take a look at:
What do you mean by turning off Sondes? your sensors? Your sensors,
may read the rs-232 flow control pins, If the port is open() then they
probably won't turn off. What ever program you write will be a lot of
string parsing to send and receive data.
I believe it is the case with all the USB/Serial adapter drivers that
the driver polls over USB the usb/serial converter device.
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