Stephen Daukas wrote:
On 5/21/07, *Karl Hiramoto* <karl@hiramoto.org <mailto:karl@hiramoto.org>> wrote:
Mike Frysinger wrote: > On 5/20/07, Stephen C. Daukas <scd@daukas.com <mailto: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
Take a look at: /usr/src/linux/drivers/usb/serial/io_edgeport.c 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. -- karl.