Subject:
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Re: Linux & RCX mini-HOWTO- comments/thoughts?
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 13 Aug 2000 05:45:06 GMT
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Viewed:
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711 times
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On Sun, 13 Aug 2000, Steve Baker wrote:
> Luis Villa wrote:
>
> > > 1) Finding a suitable serial port for the tower.
> > > This isn't always easy because there are only two free
> > > interrupts on the PC and Linux doesn't like driving two ports
> > > from one interrupt. Hence, your mouse and your modem (which are
> > > both serial devices in all probability) may prevent you from using
> > > the serial port connector on the back of the PC directly. For me,
> > > the answer was to connect the tower to my son's PC and write a
> > > shell script to redirect NQC commands to his PC for execution and
> > > download. There may be a better way - but some discussion of this
> > > somewhere would be useful.
> >
> > Any suggestions as to what exactly I should add? I've never had problems
> > of the type you describe, either with IRQ shortages or with serial port
> > conflicts, nor am I aware of any legOS users who have. So, I'm not sure
> > exactly what kinds of warnings or suggestions I should add. Let me know,
> > and I'll be glad to :)
>
> Well, I'm not 100% up to speed on the problem...but here is my (non-authoritative)
> spin on it:
>
> * On standard PC hardware, there are FOUR addresses that can be serial ports.
>
> * However, there are only TWO interrupt lines.
Ah, you meant to the serial ports. That makes more sense (to me) now.
> * Under Windoze/DOS, this somehow doesn't matter - so you can have four
> serial devices.
>
> * Under Linux, this somehow DOES matter - so you can only have two.
<pouts> That's unusual. I trust our gurus to be better than theirs. :)
> * Some kinds of mouse and some kinds of modem appear to the machine
> as serial ports.
Yes, I believe that /dev/modem is (at least under RH) linked to /dev/ttyS0
by default. Having lived on a fat /dev/eth0 pipe all my Linux-using life,
this has never been a problem for me.
> * Hence, if you have both a mouse and a modem, you may find that plugging
> the Lego IR tower into one of the two ports on the back of the machine
> will cause either the mouse or your modem to stop working.
I suppose if both were on /dev/ttyS0 that would make sense :(
> I have no idea whether there is a way around this - or whether it's
> really fundamental. You should probably check these facts out with
> someone who knows before stating them as gospel truth though.
Anyone? Anyone?
> One piece of advice I'd give is to make a symbolic link from whatever
> hardware port you find to /dev/rcx - eg:
>
> ln -s /dev/ttyS3 /dev/rcx
> chmod a+rw /dev/rcx
Interesting suggestion. I'll note it. However, that will break at least
some tools, which assume that the device is connected to /dev/ttyS0.
> > Honestly, my Lego CD-ROM has never seen the
> > light of day, so while I'm aware of the need for the firmware, I'm only
> > very peripherally aware :) Is there any other need for the CD under any of
> > the other softwares or is that one file the only thing?
>
> No - I think that's the only file from the CD that's of any use to a Linux
> user - but I don't know if any other Linux software needs it. Although
> I plan to switch to LegOS sometime soon, I've really only played with NQC.
Woohoo! Another user sees the legOS light :) Of the options I've listed in
the HOWTO, 3 (NQC, RCX.pm, and TCL) need the firmware and 3 (pbForth,
legOS, and TinyVM) do not. Since I am mainly a legOS user, I have no idea
about the use of other files- I'm pretty sure not, but at least a couple
of my other legOS-centric assumptions have already been shredded
tonight... fire away on this one if you can :)
Luis
-----------------------------------------------------------------------
"Summertime... and the living is easy...
fish are jumping and the cotton is high...
So hush, little baby, baby don't you cry."
-Ella
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Message has 1 Reply:
 | | Re: Linux & RCX mini-HOWTO- comments/thoughts?
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| (...) I'm not sure this is true. In the kernel compile options, under "Extended dumb serial driver options", there is a choice for "Support for sharing serial interrupts". There's also a "Support more than 4 serial ports" option. (24 years ago, 13-Aug-00, to lugnet.robotics)
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