LDP
/
old-www
1
1
Fork 0
Code Issues Pull Requests Releases Wiki Activity
old-www/LDP/LG/issue96/TWDT.html

3284 lines
123 KiB
HTML
Raw Permalink Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML><HEAD><TITLE> Linux Gazette Table of Contents LG #96</TITLE></HEAD>
<BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#0000AF"
ALINK="#FF0000" >
<center>
<!-- A HREF="http://www.linuxgazette.com/">
<H1><IMG SRC="../gx/newlogo.jpg" ALT="LINUX GAZETTE" border="0"></H1></A> -->
<A HREF="http://www.linuxgazette.com/">
<H1><IMG ALT="LINUX GAZETTE" SRC="../gx/lglogo.png"
WIDTH="600" HEIGHT="124" border="0"></H1></A>
<H2>November 2003, Issue 96 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
Published by <I>Linux Journal</I></H2>
<A HREF="../index.html">Front Page</A> &nbsp;|&nbsp;
<A HREF="../index.html">Back Issues</A> &nbsp;|&nbsp;
<A HREF="../lg_faq.html">FAQ</A> &nbsp;|&nbsp;
<A HREF="../mirrors.html">Mirrors</A> <!-- &nbsp;|&nbsp; --><BR>
<A HREF="../tag-kb.html">The Answer Gang knowledge base</A> (your Linux questions here!) <!-- &nbsp;|&nbsp; --><BR>
<A HREF="http://www.linuxgazette.com/search.html">Search (www.linuxgazette.com)</A>
<!-- *** BEGIN mirror site search link *** -->
<!-- &nbsp; <A HREF="http://www.linuxgazette.com/search.html">(SITE.COM
mirror)</A> -->
<!-- *** END mirror site search link *** -->
</CENTER>
<HR NOSHADE>
<!--=================================================================-->
<!-- H1><font color="#BB0000">Table of Contents:</font></H1 -->
<!-- *** BEGIN toc *** -->
<UL>
<LI> <A HREF="ecol.html">Ecol</A>, <EM>by Javier Malonda</EM>
<LI> <A HREF="hughes.html">Linux Radio Station</A>, <EM>by Phil Hughes</EM>
<LI> <A HREF="artime.html">Designing a Scientific Poster with Xfig and TEX</A>, <EM>by C.E.C. Artime, J.A. Baro</EM>
<LI> <A HREF="pramode.html">Servo motors, Linux/RTAI and other fun stuff</A>, <EM>by Pramode C.E</EM>
<LI> <A HREF="dorgan1.html">Quick and dirty guide to debugging tcp/ip</A>, <EM>by David Dorgan</EM>
<LI> <A HREF="dorgan2.html">A quick and Dirty guide to extending snmp</A>, <EM>by David Dorgan</EM>
<LI> <A HREF="dorgan3.html">The state of software security</A>, <EM>by David Dorgan</EM>
<LI> <A HREF="dorgan4.html">SSH with keys</A>, <EM>by David Dorgan</EM>
<LI> <A HREF="dorgan5.html">Using Screen</A>, <EM>by David Dorgan</EM>
<LI> <A HREF="bhargava.html">Linux as a RTOS</A>, <EM>by Nikhil Bhargava</EM>
<LI> <A HREF="baxter.html">Csound: An Interview with Dr. Richard Boulanger</A>, <EM>by Michael Baxter</EM>
</UL>
<!-- *** END toc *** -->
<HR NOSHADE>
<!--=================================================================-->
<A HREF="TWDT.txt.gz">TWDT 1 (gzipped text file)</A><BR>
<A HREF="TWDT.html">TWDT 2 (HTML file)</A><BR>
are files containing the entire issue: one in text format, one in HTML.
They are provided
strictly as a way to save the contents as one file for later printing in
the format of your choice;
there is no guarantee of working links in the HTML version.
<HR NOSHADE>
<!--=================================================================-->
<center>
<I>Linux Gazette</I><img alt="[tm]" src="../gx/tm.gif">,
<A HREF="http://www.linuxgazette.com/">http://www.linuxgazette.com/</A><BR>
This page maintained by the Webmaster of <I>Linux Gazette</I>,
<A HREF="mailto: webmaster@linuxgazette.com"> webmaster@linuxgazette.com</A>
<P>
<H5>Copyright &copy; 1996-2003 Specialized Systems Consultants, Inc.</H5>
</center>
<HR NOSHADE>
<!--=================================================================-->
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">Ecol</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/malonda.html">Javier Malonda</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
The Ecol comic strip is written for <A
HREF="http://escomposlinux.org">escomposlinux.org</A> (ECOL), the web site tha
t supports, es.comp.os.linux, the Spanish USENET newsgroup for Linux. The
strips are drawn in Spanish and then translated to English by the author.
<P>
<EM>These images are scaled down to minimize horizontal scrolling.
To see a panel in all its clarity, click on it.</EM>
<P>
<A HREF="misc/ecol/ecol-132-e-as.png">
<IMG ALT="[cartoon]" SRC="misc/ecol/ecol-132-e-as.png"
WIDTH="640" HEIGHT="240"></A>
<BR CLEAR="all">
<A HREF="misc/ecol/ecol-131-e-as.png">
<IMG ALT="[cartoon]" SRC="misc/ecol/ecol-131-e-as.png"
WIDTH="640" HEIGHT="240"></A>
<BR CLEAR="all">
<A HREF="misc/ecol/ecol-129-e-as.png">
<IMG ALT="[cartoon]" SRC="misc/ecol/ecol-129-e-as.png"
WIDTH="640" HEIGHT="240"></A>
<BR CLEAR="all">
<A HREF="misc/ecol/ecol-128-e-as.png">
<IMG ALT="[cartoon]" SRC="misc/ecol/ecol-128-e-as.png"
WIDTH="640" HEIGHT="240"></A>
<BR CLEAR="all">
<P>
All Ecol cartoons are at
<A HREF="http://tira.escomposlinux.org/">tira.escomposlinux.org</A> (Spanish),
<A HREF="http://comic.escomposlinux.org/">comic.escomposlinux.org</A> (English)
and
<A HREF="http://tira.puntbarra.com/">http://tira.puntbarra.com/</A> (Catalan).
The Catalan version is translated by the people who run the site; only a few
episodes are currently available.
<P> <SMALL>These cartoons are copyright Javier Malonda. They may be copied,
linked or distributed by any means. However, you may not distribute
modifications. If you link to a cartoon, please <A
HREF="mailto:jmr@escomposlinux.org">notify</A> Javier, who would appreciate
hearing from you.
</SMALL>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<!-- P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
</em>
<br CLEAR="all" -->
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, Javier Malonda.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">Linux Radio Station</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/hughes.html">Phil Hughes</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
In late September I wrote an article about
<a href="http://www.linuxjournal.com/article/7168" target="_blank">
radio station automation</a>
for the <i>Linux Journal</i> web site. You can find the article
The comments I received indicates that there is interest.
What I would like to do here is to see if there are some people who
would actually be interested in working on such a project.
I have establesed a palce on the
<a href="http://projects.linuxgazette.com">LG Projects Wiki</a> to further
develop this work.
<p>
The comments the article received indicated that many of the pieces were
in place.
Most I knew about and this didn't surprise me.
However, I want to build a solution rather than present a shopping list.
That solution has to include various pieces of software, all playing
together along with support.
The pieces I see are:
<ul>
<li> Audio conversion tools
<li> Audio editor
<li> Streamer
<li> Station automation
<li> Logging
<li> Transmitter
</ul>
The first three items are pretty obvious and there are lots of choices
out there.
Logging is equally obvious.
The other two items warrant further discussion once I get the basic
concepts out.
<h2>Customer Base</h2>
<p>
You can look at this potential customer base in three ways:
<ul>
<li> Where you can get some money from
<li> What sort of fun code you can write
<li> What good political ends you can reach
</ul>
<p>
The market is huge and very diverse.
As a result of that diversity there are lots of choices of where you
would like to fit into this project.
For example, if you have a political ax to grind, helping your favorite
political or religious cause get a radio voice or build a more efficient
radio voice is likely your place.
If, however, you just want to be in it for the money, there are tens of
thousands of radio stations that could use your help and would pay for
it.
<p>
Just looking at FM broadcast stations, there are 100 available
frequencies on the band.
In the US, these frequencies are allocated based on the signal
strength of other stations on the same and adjacent frequencies.
I don't have the numbers handy but that easily means thousands of
stations in the US alone.
Toss in AM broadcast and shortwave stations and you have the potential
customer base for a product.
If that isn't enough, Internet-only stations could use the same system.
<p>
Hopefully, if you are still reading, this is starting to make sense.
I willdescribe the overall project idea and then talk about the
specifics from above.
<h2>An Overall Look</h2>
<p>
Let me present how a traditional radio station works.
By traditional, I mean how stations have worked for many years.
That will make it easier to see where automation makes sense.
<p>
A typical station is composed of one or more studios
and a transmitter facility.
A studio is nothing more than a soundproof room with some audio
equipment.
The transmitter may be in the same building or at a remote location
connected by a dedicated wire or radio link.
While there is some room for talking about the transmitter link, I want
to concentrate on the studio end.
<p>
Generally, one studio will be <i>live</i>.
That means whatever is
happening in that studio will be sent directly to the transmitter.
The alternative to a live studio would be the
station either re-broadcasting some external feed or something that
they have pre-recorded.
In any case, whenever the transmitter is on the air, there must be some
source of program material.
Additional studios are available to build the pre-recorded program
material.
<p>
Each studio will likely contain one or more live microphones, multiple
sources for pre-recorded material (CD players, turntable and tape
decks) and something to record a program (tape recorder or mini-disk are
the most common).
Also included is a audio mixer board and monitor system so multiple
sources can be mixed and edited.
<p>
Small stations will typically have one studio with a person that queues
and starts pre-recorded sources and makes live announcements that can
include news and weather.
For a typical music station, the majority of this person's time is spent
waiting for the current song to end so they can queue the next one
possibly inserting some commentary between songs.
They may also be logging what they play so the station can pay the
necessary royalties.
<h2>Station Automation</h2>
<p>
This is the most obvious piece of the system--replacing the live tedium
of queuing CD tracks with an automated system.
The most basic step would be to just save all the tracks on a disk in
a computer system and allow the person to pre-select what they would
like played during a specified time block.
This is relatively trivial to do.
We can, however, do a lot more than this.
<p>
Most stations develop a play list that the live DJs need to follow.
This list includes songs that can be played along with guidelines for
how often they can be played.
Armed with that list, a program could easily make all the necessary
decisions to offer what appears to be a random selection of music within
the necessary constraints.
<p>
Next comes the announcements.
They can be divided into:
<ul>
<li> Commercials
<li> Information that will be supplied live or almost live
<li> Information that could be automated
</ul>
<p>
Automation of commercials is not much different than the music play
lists.
The primary difference is that there will likely be specific times when
a commercial must be broadcast.
Nothing magic here--just another type of event to put into a scheduling
program.
<p>
The live or almost live program material is that which must be put
together by a person.
For example, a news broadcast.
This could either be done live by a person in the studio (or remotely
over an Internet connection) or it could be pre-recorded.
If the news was pre-recorded as a set of items then later news
broadcasts could re-use the appropriate portions of a previous
broadcast.
In any case, there is still nothing particularly difficult about
this--it is just another event to schedule.
<p>
I separated out information that could be automated because it is an
additional project.
That is, it does not have to be part of this original package.
Two things come to mind here:
<ul>
<li> Time announcements
<li> Weather
</ul>
<p>
Both of these announcements are really nothing more than building a
human voice announcement out of some digital data.
Both have been done--it just becomes a matter of integration.
<p>
Some stations allow call-in requests.
This means a human responds to a request, checks to see if the song is
available and hasn't been played more than is considered correct by the
play list and then schedules it.
This seems like a perfect place to use a web page.
Listeners could place the requests and the software would appropriately
adjust what was to be played.
If the requested material was not available it could advise you of that
fact or even order heavily requested material.
<h2>Transmitter</h2>
<p>
While a traditional transmitter is far away from the scope of this
project, a transmitter option deserves mention.
In my searching for FM broadcast transmitters for a project in Nicaragua
I ran across a company that offers an FM broadcast transmitter on a PCI
card.
They have a new card on the way and I have offered to write the Linux
driver for it.
<p>
If you saw this project as <i>just fun</i> or something that would work
for your college dorm, a card such as this might be just the ticket.
You could offer a web interface to select program material and broadcast
to nearby FM receivers.
Being a <i>radio guy</i> as well as a computer guy, this interests me a
lot.
<h2>Overall Scope</h2>
<p>
That covers all the pieces from the geek end.
But, as I said in the beginning, I want to present a solution rather
than a shopping list.
That 100mw station in your basement that your family can listen to is
not going to be a good commercial customer but tens of thousands of
commercial stations certainly could be.
<p>
Integrating all the software necessary to offer a solution is the first
part.
Installation and support comes next.
A radio station that has full-time employees running the station and
advertisers paying hundreds or thousands of dollars for a commercial
will quickly see the benefits of a system such as this.
The biggest hurdle will be showing them that the solution will be
supported.
That is, that their station will not be off the air because they made
this choice.
<p>
For a small station, this might mean knowing that they could call
someone and have them come in and fix a problem.
For a larger station it could mean training of on-site personnel.
There are other levels of support including spare systems, shared
servers and so forth.
In other words, an assortment of different markets where the same
software is offered but the support potential varies.
<h2>What next?</h2>
<p>
That's up to you.
I am excited about the project.
Unfortunately, I have a "day job" which does not give me the necessary
time to put all this together and even if it was together, I don't want
to go into the software support business.
<p>
My hope is that the right people are out there that want to do the
pieces.
That is my real reason for writing this article.
I am happy to offer input, help set direction, offer a mailing list of
discussion forum and even publicize the product.
If you are interested in participating, write at <a
href=<EFBFBD>mailto:phil@ssc.com">phil@ssc.com</a> and let me know your
interests.
Or go out to the
<a href="http://projects.linuxgazette.com">LG Projects Wiki</a>
and chime in.
Maybe Linux-controlled radio will be here before you know it.
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
Phil Hughes is the publisher of <I>Linux Journal</I>, and thereby <I>Linux
Gazette</I>. He dreams of permanently tele-commuting from his home on the
Pacific coast of the Olympic Peninsula.
As an employer, he is &quot;Vicious, Evil,
Mean, & Nasty, but kind of mellow&quot; as a boss should be.
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, Phil Hughes.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">Designing a Scientific Poster with Xfig and TEX</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/artime-baro.html">C.E.C. Artime, J.A. Baro</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html lang="en">
<head>
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">
<meta name="author" content="Carleos Artime">
<meta name="generator" content="bhl2html">
<link rel="generator-home" href="http://www.nongnu.org/bhl">
<title>Designing a scientific poster</title>
</head>
<body>
<h1 align="center">Designing a scientific poster with Xfig and
T<small>E</small>X</h1>
<p>A traditionally geeky user base has made the free software
panorama plenty of scientifical tools. A key feature of
scientific work is public defense of reseach methods and results
in scientific meetings, and this is usually accomplished by
means of oral presentations or posters. Both require the
authors to develop some visual support: slide shows for oral
presentations, with plenty of tools available (<a
href="http://www.openoffice.org">OpenOffice</a>, <a
href="http://www.latex-project.org">L<sup><small>A</small></sup>T<small>E</small>X</a>,...),
and a poster proper for the poster sessions. These take the
form of an A0-sized paper sheet, and a visual exposition of the
materials involved is crucial. </p>
<p> A general tool for manipulating images, as <a
href="http://www.gimp.org">the GIMP</a>, can be very useful
when most of the poster is to be filled with photos and
analogic images. Notwithstanding, scientific graphics are
best handled with a vectorial graphics tool. This article
will present a brief review of tools for incorporating
graphics in scientific posters. </p>
<img src="misc/artime/gimp0.png" alt="The GIMP interface"
width="800" height="600">
<h2>Designing: Xfig</h2>
<p> The GIMP is a bitmap- or raster-oriented tool, and as such,
aimed at dealing with individual pixels. This approach is
suitable for photos and artistic material. Technical drawings
take a rather different approach: they are better described by
their geometric elements, rather than by their constitutive
pixels. This "vectorial" approach has the additional advantage
that it produces resolution-independent graphics, thus allowing
arbitrary zooming and enlargement. </p>
<img src="misc/artime/gimp1.png" alt="Gfig: the GIMP vectorial tool"
width="776" height="554">
<p> Several free vectorial programs are currently available: <a
href="http://sodipodi.sourceforge.net">Sodipodi</a>, <a
href="http://www.koffice.org/karbon">Karbon14</a>, <a
href="http://sketch.sourceforge.net">Sketch</a>... Some
integrate nicely with the <a
href="http://www.gnome.org">Gnome</a> and <a
href="http://www.kde.org">KDE</a> desktop environments. Even
the GIMP, since version 1.2, includes a plug-in enabling quite
elaborate vectorial design, <a
href="http://www.picnic.demon.co.uk/gfig/gfig_main.html">Gfig</a>;
it lies under the menu (Filters-&gt;Render). However, the
classic among X Window applications is <a
href="http://www.xfig.org">Xfig</a>.
</p>
<img src="misc/artime/xfig0.png" alt="The Xfig initial screen"
width="790" height="544">
<p> Xfig is a thoroughly proven program that makes use of the X
Athena widget toolkit. Thus, it is a very mature product and,
consequently, its stability is beyond doubt. This is a highly
appreciated feature as work on posters frequently goes on until
the very dead line. </p>
<p> A further consequence of being a mature project is that Xfig
has been enriched by contributions of a wide community of users.
This has produced a comprehensive set of galleries for various
fields (electronics, UML, music, maps, etc.). </p>
<p> It is a reliable program as it stores its information in a
readily accessible text format, from which information retrieval
is quite straightforward. This kind of format does not follow
the modern trend, that is, it is not a SGML-based system.
Rather, it consists of the minimal amount of information for
describing the graphic, stored as ASCII characters. A thorough
description is available, e.g., at <a
href="http://www.xfig.org/userman/fig-format.html">The FIG file
format</a> or, in a <a href="http://www.debian.org">Debian</a>
system, in the file <tt>/usr/share/doc/xfig/FORMAT3.2.gz</tt>.
Its regularity makes it suitable to be processed with the
classical Unix/<a href="http://www.gnu.org">GNU</a> text
filters: <a href="http://www.gnu.org/software/sed">sed</a>, <a
href="http://www.gnu.org/software/gawk">awk</a> and such. So
chances are that you prefer ASCII to the XML format. On the
other hand, important applications as <a
href="http://www.gnuplot.info">Gnuplot</a> and GNU <a
href="http://www.gnu.org/software/plotutils">plotutils</a> can
produce FIG files; a comprehensive list is available in the file
FIGAPPS, within the Xfig distribution.</p>
<p> Another nice feature of Xfig lies with its ability to export
using L<sup><small>A</small></sup>T<small>E</small>X friendly
formats. This is true for both text and graphics. A
&#8220;special flag&#8221; is assigned to each piece of text,
signaling whether it is to be exported 'raw' or 'as <a
href="http://www.tug.org">T<small>E</small>X</a>'. Graphics are
coded according to the
L<sup><small>A</small></sup>T<small>E</small>X package options
chosen by the user. More on this later, so keep reading or look
up the LATEX.AND.XFIG and PDFLATEX.AND.XFIG files in the Xfig
distribution
</p>
<p>In order to be fair, it is time now to expose some
not-so-desirable Xfig features. It did not age badly, it is
rather that Xfig drags several drawbacks inherited from old
techniques. </p>
<p>Users of modern programs will certainly get dissapointed by its
single level of undo. So it pays to be a little cautious when
designing. </p>
<p> As mentioned above, Xfig makes use of Athena widgets, and
suffers from their limilations. For example, it is not easy to
handle accented characters in dialog windows (as when using the
Edit tool), a very frustrating feature for most European users.
Note that it allows the use of the Meta key as a Compose key,
thus permitting accented characters when using the Text tool on
the canvas. </p>
<p> On the other hand, Xfig handles a lot of export formats. In
fact, some of them are especially useful for
L<sup><small>A</small></sup>T<small>E</small>X users. However,
its support for modern graphic formats, like XML-based SGV
(Scalable Vector Graphics), is still experimental. </p>
<h2>Post-processing</h2>
<h3>L<sup><small>A</small></sup>T<small>E</small>X</h3>
<p> L<sup><small>A</small></sup>T<small>E</small>X is a set of macros
built on the top of the T<small>E</small>X typesetting
system. It is widely used to publish scientific papers, reports
and books. Despite many users are unaware, slides are easily
composed too. However, designing a full poster with
L<sup><small>A</small></sup>T<small>E</small>X alone is a
daunting task, as many objects must be arranged in a 2D space
with possibly complex interconnections among them. So the
composition can be visually arranged with Xfig, and lately
refined with a T<small>E</small>X editor. </p>
<p>To facilitate the integration of the visual work with the
edition of T<small>E</small>X source code, Xfig users are
empowered with a broad range of options. First, they have the
choice of exporting a file as either a
L<sup><small>A</small></sup>T<small>E</small>X chunk or as a
complete L<sup><small>A</small></sup>T<small>E</small>X file.
Second, a given graphical element is possibly translated to
several T<small>E</small>X expressions, depending of which
macros are available or are preferred by the user; this point is
discussed in the next paragraph. </p>
<h3>fig2dev</h3>
<p>The Xfig web site also hosts <tt>transfig</tt>, which includes
a program to export from Fig format to several
&#8220;devices&#8221;, <tt>fig2dev</tt>. This functionality is
available from the GUI as well, under the Export option of the
File menu. As we intend to finally automatize the full task as
much as possible, emphasis is put on the stand-alone
program.</p>
<p> Transformation of Fig documents into T<small>E</small>X
elements can be accomplished in several ways. Each way differs
in the number of graphical elements it can deal with (for
example: rotated text, filled rectangles), at the cost of
requiring more sophisticated
L<sup><small>A</small></sup>T<small>E</small>X packages: epic,
eepic, eepicemu, pictex. The best results are obtained with
combined <a
href="http://www.cs.indiana.edu/docproject/programming/postscript/postscript.html">PostScript</a>
(or <a
href="http://www.adobe.com/products/acrobat/adobepdf.html">PDF</a>)
and TeX: this assures that all elements seen in the Xfig screen
will be present in the printable output. Two warnings:
<em>specially flagged</em> text will be shown as raw
T<small>E</small>X in Xfig, but nicely typeset in the final
document; and some previewers, as Xdvi (distributed with <a
href="http://www.tug.org/teTeX">teT<small>E</small>X</a>), are
not able to represent some kinds of elements, as rotated text,
so better use <tt>dvips</tt> and a PostScript viewer.</p>
<h3>dvips</h3>
<p> Processing a T<small>E</small>X file produces by default DVI
format files, standing for DeVice Independent. This format is
ready to be transformed into the set of displaying instructions.
The most widespread format for final documents is PostScript,
featuring a complete programming language understood by almost
every high-quality printer. </p>
<p> The program <tt>dvips</tt> converts a DVI file into a
PostScript, and is distributed with the main T<small>E</small>X
packages, like <tt>tetex</tt>. It allows several interesting
options, giving access to the powerful features of PostScript.
One of them is the ability of setting the paper size, be it in a
measure unit, as cm, or by a standard name, as A1. This feature
is accessed by the <tt>-t</tt> and <tt>-T</tt> options. </p>
<h3>poster</h3>
<p> The output of <tt>dvips</tt> is fine if one has access to an
A0-size capable printer. This is often not the case. An
acceptable alternative would be printing 16 A4 pages, or 8 A3
pages. The <tt>poster</tt> package tiles a one-page PostScript
into small pieces, that can be pasted together to form the whole
image. Guide lines indicating where to apply the guillotine
cutter are printed as well. <a
href="http://printing.kde.org/downloads/"><tt>Poster</tt></a> is
available at the KDE web site, and as a Debian package.
<h3>psresize</h3>
<p> Should we give away small copies of our poster,
<tt>psresize</tt> is the tool of choice to build them. It is
included in the <a
href="http://gershwin.ens.fr/vdaniel/Doc-Locale/Outils-Gnu-Linux/PsUtils/"><tt>psutils</tt></a>
Debian package. </p>
<h3>bash</h3>
<p> The entire process must be repeated if any change is made in
the Xfig drawing. We suggest that you consider seriously the
little extra work of gluing all the steps mentioned through a
shell script. <a href="misc/artime/poster.sh.txt">Here</a> we
present one developed for the most widespread shell, GNU <a
href="http://www.gnu.org/software/bash"><tt>bash</tt></a>.
Calling the following script from within the directory
containing the Fig file, the whole proccess is performed. Note
that it appends a L<sup><small>A</small></sup>T<small>E</small>X
preamble and postamble, required by several
L<sup><small>A</small></sup>T<small>E</small>X features used by
the author, and several other as required by Xfig exports. </p>
<p>(We just realised the inclusion of a simple script meant to
perform the conversion from the Fig format to an EPS,
<tt>TeXfig2eps</tt>, in the Xfig distribution. As our
discussion shows, it may not be enough in many cases.)</p>
<pre>
#!/bin/bash
################################################
# Processes the FIG source file for the poster #
################################################
######################################################
# #
# Usage: #
# 1. Design a poster with Xfig. #
# 2. Save it as a normal FIG file, with #
# the name, e.g., `myfile.fig'. #
# 3. Substitute `BASE=myfile' for the line #
# `BASE=poster' in this script. #
# 4. Run this script within the directory #
# where `myfile.fig' lies. #
# 5. The output files will be: #
# `myfile-a0.ps' - one poster-sized page #
# `myfile-a4-1.ps' - a4-sized mini-poster #
# `myfile-a4-16.ps' - sixteen tile pages #
# #
######################################################
# basename
BASE=poster
# convert the FIG into LaTeX + PostScript
echo '
\documentclass{article}
\usepackage{amsmath} % symbols and equations
\usepackage{amsfonts} % needed for blackboard characters
\usepackage[spanish]{babel} % titles in our language
\usepackage[latin9]{inputenc} % accented characters
\usepackage[a0paper,margin=0cm,nohead,nofoot]{geometry} % margins
\usepackage{graphicx} % including figures
\usepackage{color} % import from Xfig
\usepackage{epic} % complements the following
\usepackage{eepic} % Xfig filling
\usepackage{rotating} % text in figures
\usepackage{type1cm} % arbitrarily sized fonts
\begin{document}
' &gt; $BASE.tex
fig2dev -L pstex $BASE.fig &gt; $BASE.pstex
echo -n '
\begin{picture}(0,0)
\includegraphics{'$BASE'.pstex}
\end{picture}
' &gt;&gt; $BASE.tex
fig2dev -L pstex_t $BASE.fig &gt;&gt; $BASE.tex
echo '\end{document}' &gt;&gt; $BASE.tex
# typeset the source LaTeX
latex $BASE
# transform into a PostScript of size almost DIN A0
dvips -o $BASE-a0.ps -T 84cm,118cm $BASE
# build the small A4 version of the poster
psresize -Pa0 -pa4 $BASE-a0.ps $BASE-a4-1.ps
# build the 16 A4 pages composing the poster
dvips -o $BASE.eps -T 84cm,118cm -E $BASE
poster -mA4 -pA0 $BASE.eps &gt; $BASE-a4-16.ps
</pre>
Some of the commands used in the script need further explanation.
The following paragraphs try to clarify these issues.
<p>
The <tt>\usepackage{color}</tt> is suggested in
<tt>/usr/share/doc/xfig/README.Debian</tt> in Debian systems.
Latest versions of Xfig's <tt>pstex</tt> use the <tt>\RGB</tt>
command for setting text's color.
<p>
Other packages were included as needed, often with a trial and
error procedure. The example does not make use of all them, but
it can be illustrative as a comprehensive list of packages that
we have ever needed for our own posters.
<p> Please note that <tt>psresize</tt> operates on <tt>.ps</tt>
files, and <tt>poster</tt> on <tt>.eps</tt> files. Thus
<tt>dvips</tt> is executed twice, without and with the
<tt>-E</tt> option.
<h2>Example</h2>
In order to exemplify the use of this script, we first create the
graphic layout with Xfig. By using the following command
<pre>
$ xfig -paper a0 -portrait
</pre>
the canvas adopts the size and orientation of the poster we need.
We design a sample poster shown <a
href="misc/artime/xfig1.png">here</a> in a screenshot capture and
<a href="misc/artime/poster.fig">here</a> in Fig format. We save
it with the name <tt>poster.fig</tt>. The <i>basename</i>
<tt>poster</tt> is assigned to the <tt>BASE</tt> variable in the
first lines of the script.
After running the script within the same directory where
<tt>poster.fig</tt> lies, the following output files are of
interest:
<ul>
<li> <a
href="misc/artime/poster-a0.ps"><tt>poster-a0.ps</tt></a>:
contains the A0-sized postcript, ready to be printed in an
A0-capable printer or plotter.
<li>
<a
href="misc/artime/poster-a4-1.ps"><tt>poster-a4-1.ps</tt></a>:
the poster scaled down to A4 size, to be printed and
distributed among the poster session attendees.
<li>
<a
href="misc/artime/poster-a4-16.ps"><tt>poster-a4-16.ps</tt></a>:
a postscript file containing sixteen A4 pages that, put
together, form the A0-sized poster.
</ul>
<h2>Very big fonts: a hack is needed</h2>
<p>
The standard <tt>tetex</tt> distribution uses by default
bitmapped fonts, which requires discrete magsteps. This leads
to warnings like
<pre>
LaTeX Font Warning: Font shape `OT1/cmr/m/n' in size <30> not available
(Font) size <24.88> substituted on input line 5.
LaTeX Font Warning: Size substitutions with differences
(Font) up to 5.12pt have occurred.
</pre>
As stated in the <tt>tetex</tt> documentation,
<tt>\usepackage{type1cm}</tt> allows the use of Computer Modern
fonts at arbitrary type sizes. It must overwrite font
definitions, so it may require to be included <em>after</em> other
packages.
<p>
Note that <tt>transfig</tt> uses a fixed set of font sizes,
handled through the macro
<pre>
#define TEXFONTSIZE(S) (texfontsizes[((S) <= MAXFONTSIZE) ? round(S)\
: (MAXFONTSIZE-1))])
</pre>
that indirectly limits the maximum size of fonts to be of 41
points. For the example being shown, we had to edit
<tt>transfig</tt>'s sources (file <tt>texfonts.h</tt>) in order to
change that macro to
<pre>
#define TEXFONTSIZE(S) (S)
</pre>
The Debian way:
<pre>
$ su
Password:
# apt-get remove transfig
Reading Package Lists... Done
Building Dependency Tree... Done
The following packages will be REMOVED:
transfig
0 packages upgraded, 0 newly installed, 1 to remove and 3 not upgraded.
Need to get 0B of archives. After unpacking 799kB will be freed.
Do you want to continue? [Y/n]
(Reading database ... 67797 files and directories currently installed.)
Removing transfig ...
# exit
$ apt-get source transfig
Reading Package Lists... Done
Building Dependency Tree... Done
Need to get 340kB of source archives.
Get:1 ftp://ftp.es.debian.org testing/main transfig 1:3.2.4-rel-4 (dsc) [652B]
Get:2 ftp://ftp.es.debian.org testing/main transfig 1:3.2.4-rel-4 (tar) [326kB]
Get:3 ftp://ftp.es.debian.org testing/main transfig 1:3.2.4-rel-4 (diff) [13.0kB]
Fetched 340kB in 1m51s (3062B/s)
dpkg-source: extracting transfig in transfig-3.2.4-rel
$ vi transfig-3.2.4-rel/fig2dev/dev/texfonts.h
$ cd transfig-3.2.4-rel/
$ dpkg-buildpackage -rfakeroot -uc -us
...
[lots of output]
...
$ cd ..
$ su
Password:
# dpkg -i transfig_3.2.4-rel-4_i386.deb
Selecting previously deselected package transfig.
(Reading database ... 67734 files and directories currently installed.)
Unpacking transfig (from transfig_3.2.4-rel-4_i386.deb) ...
Setting up transfig (3.2.4-rel-4) ...
# exit
</pre>
<p>
If you find this method cumbersome, you can have a look at this
<a
href="http://www.stsci.edu/ftp/software/tex/posters/">directory</a>
where a style file meant to produce big fonts for big pages
(posters) can be found.
</body>
</html>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
C.E.C. Artime is a GNU fan and a free software advocator since 2000.
<br>
J.A. Baro is a Linux user and a Perl hacker since 1996.
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, C.E.C. Artime, J.A. Baro.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">Servo motors, Linux/TRAI and other fun stuff</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/pramode.html">Pramode C.E</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<html>
<head>
<title>Servo motors, Linux/RTAI and other fun stuff</title>
</head>
<body>
<h2>Introduction</h2>
<p>
In last month's <a href="http://www.linuxgazette.com/issue95/pramode.html">article</a>, I had explored the problems
associated with writing timing sensitive code under Linux and looked at
how <a href="http://www.aero.polimi.it/projects/rtai">RTAI</a> solves them in an elegant manner.
In this issue, I present an interesting application developed by
a few of my students as part of a Computer Vision project. I would
also like to share with you a few programs which I wrote in my
effort to understand RTAI better:
<ul>
<li>A simple program which measures pulse width of a PWM signal
<li>A frequency counting program which uses interrupts under RTAI
<li>A program which tries to demonstrate the effect of priority
inversion in multithreaded code and the use of resource semaphores
under RTAI (The reader is expected to have an understanding of basic semaphore
operations to follow this part).
</ul>
</p>
<h2>The Project</h2>
<p>
In his article <a href="http://www.fsmlabs.com/articles/camera/rtlcam.html">Creating a web page controlled 2-axis movable camera with
RTLlinux/Pro</a>, Cort Dougan presents the software and hardware involved in the
construction of an interesting device which allows him to always keep an eye on his pet cat,
Kepler. An ordinary web cam is controlled by two servo motors - one makes the cam
move up and down and the other makes it sweep 180 degrees. The movement of both the
servos is controlled by real time tasks.
<p>
Motivated by the article, a few of my students tried their hand at
designing such a system. Here is what they came up with:
<p>
<img src="misc/pramode/cam1.jpg">
<p>
The top and bottom servo's should be clearly visible - the one at
the bottom serves to rotate the platform resting on its axis (the
platform on which the webcam is mounted). The
whole thing is made out of transparent plastic. Here is a closer view
of the bottom part:
<p>
<img src="misc/pramode/cam2.jpg">
<h3>Controlling the servo</h3>
<p>
A hobby <a href="http://www.seattlerobotics.org/guide/servos.html">servo motor</a>(like the Futaba S2003 used in this project)
runs off 5V DC, has high torque for its size and can be positioned
at points along a 180 degree arc (or a little bit more - the servo
doesn't rotate the full 360 degrees, there is some kind of
mechanical `stop' built into it - which can of course be removed
if you are seriously into <a href="http://www.seattlerobotics.org/guide/servohack.html">servo hacking</a>).
The control wire (normally white colour)
of the servo should be continuously fed with a digital signal whose
period is about 20ms - the period need not be very accurate,
and can be lesser than 20ms, but the on time should be precisely
controlled, it is what decides where the servo will move to - in
this case, it was seen that the servo moves for about 170 degrees
for an on time from 2.2ms down to 0.5ms. Here is a picture of the
control pulse:
<p>
<img src="misc/pramode/pwm.png">
<p>
Generating this control pulse with `normal' Linux is a difficult
issue - other activities going on in the system can seriously
disturb the waveform - with the result that the servo will start
reacting violently. So, hard real time RTAI tasks are used.
<p>
Two real time tasks are used to control the servos - one
controlling the top servo and the other one, the bottom
servo. The servo position is communicated to the real time
tasks from user space with the help of two real time fifos.
Let's first look at some macro/variable definitions (the actual
rotation angles have not been accurately measured - so users
of the Futaba S2003 need not be worried about any numerical
discrepancy):
<pre>
#define BOTTOM_SERVO_FIFO 0
#define TOP_SERVO_FIFO 1
#define FIFO_SIZE 1024
#define BOTTOM_SERVO 0
#define TOP_SERVO 1
#define BOTTOM_SERVO_PIN 2 /* Bit D1 of parport o/p register */
#define TOP_SERVO_PIN 4 /* Bit D2 of parport o/p register */
#define TICK_PERIOD 1000000 /* 1 ms */
#define STACK_SIZE 4096
#define MIN_ON_PERIOD 500000 /* .5 ms */
#define NSTEPS 35
#define STEP_PERIOD 50000 /* 50 micro seconds */
#define TOTAL_PERIOD 20000000 /* 20ms */
#define ONE_SHOT
RTIME on_time[2], off_time[2];
RT_TASK my_task1, my_task2;
</pre>
The bottom servo is connected to pin 3 of the parallel port and the
other one, to pin 4 - the macro's BOTTOM_SERVO_PIN and TOP_SERVO_PIN
define the values to be written to the parallel port data register
to set these pins (bit D0 of parallel port data register controls pin
number 2, bit D1 pin number 3 and so on - the macro's are definitely
poorly named and meant to confuse readers). The minimum on period of the
control pulse is defined to be 500000 nano seconds (.5 ms). Because
we get a servo rotation of 170 degree for pulse widths from 0.5ms to
2.2ms, a 50 micro second change in pulse width gives us 5 degree of
rotation. We define the `zeroth step' of the servo as the position
to which it moves when it sees a pulse of 0.5ms duration and the
`thirty-fourth step' as the position it moves to when it sees a
pulse whose on time is 0.5ms + (50 micro second * 34), ie, 2.2ms. So, in
a total of 35 steps, each step about 5 degree, we get full 170 degree
rotation. What the user program communicates with the real time tasks
through the fifos is this step number.
<p>
The total period is defined to be 20ms. The zeroth element of the on_time
array stores the current on time of the pulse which controls the
bottom servo and the first element, that of the top servo. Similar
is the case with the off_time array.
<p>
Let's now look at the code for the tasks which control the servo's:
<pre>
static void servo_task(int pin)
{
while(1) {
outb(inb(0x378) | pin, 0x378);
rt_sleep(on_time[(pin &gt;&gt; 1) - 1]);
outb(inb(0x378) &amp; ~pin, 0x378);
rt_sleep(off_time[(pin &gt;&gt; 1) - 1]);
}
}
</pre>
The argument to the task is BOTTOM_SERVO_PIN or TOP_SERVO_PIN,
depending on which servo it controls. The servo number can be
obtained from these values by shifting them right once and subtracting
one. First, the corresponding parallel port pin is made high and
a sleep is executed - then, the pin is made low and the task goes
to sleep once again.
<p>
Let's now look at the fifo handler code - user programs communicate
with the real time tasks through two fifo's - one for each servo. The
fifo handler code, which gets executed when either of them is written
to from a user space program, is the same. User programs communicate
a `step number', ie, an integer in the range 0 to 34.
<pre>
int fifo_handler(unsigned int fifo)
{
int n, r;
unsigned int on;
r = rtf_get(fifo, &amp;n, sizeof(n));
rt_printk("fifo = %d, r = %u, n = %u\n", fifo, r, n);
if((n &lt; 0) &amp;&amp; (n &gt; 34)) return -1;
on = MIN_ON_PERIOD + n*STEP_PERIOD;
on_time[fifo] = nano2count(on);
off_time[fifo] = nano2count(TOTAL_PERIOD - on);
return 0;
}
</pre>
The code should be easy to understand, it simply reads a step number,
converts it into a corresponding `on time' and stores it into the proper
slot in the on_time array. The argument to the handler is the number
of the fifo to which data was written to from the user space program.
<p>
We now come to the module initialization part, the code should be easy
to understand.
<pre>
int init_module(void)
{
RTIME tick_period;
RTIME now;
rtf_create(BOTTOM_SERVO_FIFO, FIFO_SIZE);
rtf_create_handler(BOTTOM_SERVO_FIFO, fifo_handler);
rtf_create(TOP_SERVO_FIFO, FIFO_SIZE);
rtf_create_handler(TOP_SERVO_FIFO, fifo_handler);
#ifdef ONE_SHOT
rt_set_oneshot_mode();
#endif
rt_task_init(&amp;my_task1, servo_task, BOTTOM_SERVO_PIN, STACK_SIZE, 0, 0, 0);
rt_task_init(&amp;my_task2, servo_task, TOP_SERVO_PIN, STACK_SIZE, 0, 0, 0);
tick_period = start_rt_timer(nano2count(TICK_PERIOD));
on_time[BOTTOM_SERVO] = nano2count(MIN_ON_PERIOD);
on_time[TOP_SERVO] = on_time[BOTTOM_SERVO];
off_time[BOTTOM_SERVO] = nano2count(TOTAL_PERIOD - MIN_ON_PERIOD);
off_time[TOP_SERVO] = off_time[BOTTOM_SERVO];
now = rt_get_time() + tick_period;
rt_task_make_periodic(&amp;my_task1, now, tick_period);
rt_task_make_periodic(&amp;my_task2, now, tick_period);
return 0;
}
</pre>
<p>
And here comes the module cleanup:
<pre>
void cleanup_module(void)
{
stop_rt_timer();
rt_busy_sleep(10000000);
rtf_destroy(BOTTOM_SERVO_FIFO);
rtf_destroy(TOP_SERVO_FIFO);
rt_task_delete(&amp;my_task1);
rt_task_delete(&amp;my_task2);
}
</pre>
<p>
The real time tasks were found to control the servo's perfectly. The
system was heavily loaded by running multiple kernel compiles, copying and untarring
large files and several other tricks - but the real time tasks were found
to perform satisfactorily.
<h2>Using Interrupts</h2>
<p>
It is easy to measure the frequency of a low-frequency square
wave. Simply apply it to the parallel port interrupt pin, write
an interrupt service routine and increment a count within the
routine. This count may be transferred to a user space program
through a real time fifo.
<p>
A real time application may not tolerate interrupts getting
missed or the interrupt handling code getting executed a long
time after the interrupt is asserted. With a `normal' Linux
kernel, this is a real problem. The Linux kernel may disable
interrupts when it executes critical sections of code - during
this time, the system remains unresponsive to external events.
In an RTAI patched kernel, even if Linux asks for interrupts
to be disabled, interrupts don't really get disabled; only thing
is RTAI does not let the Linux kernel see the interrupt. A
real time task will still be able to handle interrupts undisturbed.
<p>
Here is a small program which counts the number of interrupts
coming on the parallel port interrupt input pin. I tested it
out by using a function generator to generate a square wave
at various low frequencies. A simple 555 timer based circuit
should also do the job.
<pre>
#include &lt;linux/module.h&gt;
#include &lt;rtai.h&gt;
#include &lt;rtai_sched.h&gt;
#include &lt;rtai_fifos.h&gt;
#include &lt;asm/io.h&gt;
#define FIFO_R 0
#define FIFO_W 1
#define TIMERTICKS 1000000000 /* 1 second */
#define STACK_SIZE 4096
#define FIFO_SIZE 1024
static int prev_total_count = 0;
static int new_total_count = 0;
static RT_TASK my_task;
static void fun(int t)
{
while(1) {
prev_total_count = new_total_count;
new_total_count = 0;
rt_task_wait_period();
}
}
int fifo_handler(unsigned int fifo)
{
char c;
rtf_get(FIFO_R, &amp;c, sizeof(c));
rtf_put(FIFO_W, &amp;prev_total_count, sizeof(prev_total_count));
return 0;
}
static void handler(void)
{
new_total_count++;
}
int init_module(void)
{
RTIME tick_period, now;
rt_set_periodic_mode();
rt_task_init(&amp;my_task, fun, 0, STACK_SIZE, 0, 0, 0);
tick_period = start_rt_timer(nano2count(TIMERTICKS));
now = rt_get_time();
rt_task_make_periodic(&amp;my_task, now + tick_period, tick_period);
rtf_create(FIFO_R, FIFO_SIZE);
rtf_create(FIFO_W, FIFO_SIZE);
rtf_create_handler(FIFO_R, fifo_handler);
rt_request_global_irq(7, handler);
rt_enable_irq(7);
outb(0x10, 0x37a);
return 0;
}
void cleanup_module(void)
{
stop_rt_timer();
rt_busy_sleep(10000000);
rt_task_delete(&amp;my_task);
rt_disable_irq(7);
rt_free_global_irq(7);
rtf_destroy(FIFO_R);
rtf_destroy(FIFO_W);
}
</pre>
<p>
The rt_request_global_irq and rt_enable_irq functions together
instruct the RTAI kernel to service IRQ 7 (which is the parallel
port interrupt). The interrupt handler simply increments a count.
Every 1 second (the frequency of our input doesn't change
fast, and we are only interested in observing a long cumulative count)
a real time task wakes up and stores this count
value to another variable (called prev_total_count) and also clears
the counter. User programs can access prev_total_count through
a FIFO.
<p>
A user program reads the count by writing a dummy value to
FIFO_R and reading from FIFO_W. Writing to FIFO_R will result
in fifo_handler getting executed, which will place the
count onto FIFO_W; it can then be read by the user program. There
should surely be a better way to do this - only trouble is,
I don't know how. Here is the user program:
<pre>
/* User space test program */
#include &lt;sys/types.h&gt;
#include &lt;sys/stat.h&gt;
#include &lt;fcntl.h&gt;
#include &lt;assert.h&gt;
#define FIFO_W "/dev/rtf0"
#define FIFO_R "/dev/rtf1"
main()
{
int fd1, fd2, dat,r;
fd1 = open(FIFO_W, O_WRONLY);
fd2 = open(FIFO_R, O_RDONLY);
assert(fd1 &gt; 2);
assert(fd2 &gt; 2);
write(fd1, "a", 1);
r = read(fd2, &amp;dat, sizeof(dat));
assert(r == 4);
printf("interrupt count = %d\n", dat);
}
</pre>
<h2>Measuring Pulse Width</h2>
<p>
Let's say we wish to measure the off-time of a pulse
of total width 3ms with an accuracy of not more than
0.1ms. We start a periodic task with period 0.1 ms. At
each `awakening' of this periodic task, it checks whether
the signal is low or high. The number of times the signal
is low, out of a total of 30 samples, is recorded.
Here is the code which implements this procedure:
<pre>
#include &lt;linux/module.h&gt;
#include &lt;rtai.h&gt;
#include &lt;rtai_sched.h&gt;
#define LPT1_BASE 0x378
#define LPT1_STATUS 0x379
#define ACK 6
#define STACK_SIZE 4096
#define TIMERTICKS 100000 /* 0.1 milli second */
#define TOTAL_SAMPLES 30 /* Take 30 samples at 0.1 ms each */
static RT_TASK my_task;
static int old_off_samples, new_off_samples;
static void fun(int t)
{
static int count = 0;
while(1) {
new_off_samples = new_off_samples + ((inb(LPT1_STATUS) &gt;&gt; ACK) &amp; 0x1);
if(++count == TOTAL_SAMPLES) {
count = 0;
old_off_samples = new_off_samples;
new_off_samples = 0;
}
rt_task_wait_period();
}
}
int init_module(void)
{
RTIME tick_period, now;
rt_set_periodic_mode();
rt_task_init(&amp;my_task, fun, 0, STACK_SIZE, 0, 0, 0);
tick_period = start_rt_timer(nano2count(TIMERTICKS));
now = rt_get_time();
rt_task_make_periodic(&amp;my_task, now + tick_period, tick_period);
return 0;
}
void cleanup_module(void)
{
stop_rt_timer();
rt_printk("old = %u, new = %u\n", old_off_samples, new_off_samples);
rt_busy_sleep(10000000);
rt_task_delete(&amp;my_task);
}
</pre>
<p>
The periodic task checks the D6th bit of the parallel port
status register. It is 1 if the input signal on the 10th
pin is low. The count could be, as usual, transferred to a
user space program through a fifo.
<h2>Semaphores and Priority inversion</h2>
<p>
Programmer's use semaphore's to synchronize the activity of
multiple threads. RTAI has a function:
<pre>
void rt_sem_init(SEM *sem, int value);
</pre>
Which can be used to create and initialize semaphore objects.
There is an interesting problem called `priority inversion'
associated with the use of locking mechanisms in an an environment
which allows preemptive execution of tasks with varying priorities.
It seems that the problem was brought to the attention of the
real time design community by certain glitches encountered during
the Mars Pathfinder Mission (a Google search would yield more
information). I shall try to describe the problem first (the description
is based on information obtained from the Net on the Pathfinder mission
failure).
<p>
Suppose we have a very high priority task, Task-H which periodically
accesses a buffer to write data to it (or read data from it). Another
task, a very low priority and very infrequently running task, which
always runs only for a short amount of time (let's call it Task-L), also
might need to access the buffer to write to or read from it. Both
these tasks would have to successfully grab a lock before one of
them is able to access the buffer; the lock can be acquired by only
one task at a time. Let's say Task-L grabs the lock and starts accessing
the buffer. In between, suppose an interrupt causes the scheduling of
the very high priority task, Task-H. Now, Task-H also would try to grab
the lock, but blocks because it is currently held by Task-L. In the normal
case, Task-L would finish very soon and release the lock, allowing Task-H
to continue. But suppose a medium priority task, Task-M gets scheduled. Now,
as long as Task-M does not finish, the OS will not allow Task-L to continue.
Only if Task-L finishes doing whatever it has to do and releases the lock
will Task-H be able to continue - the result is Task-H gets delayed by
the time Task-M would take to complete. Suppose the system designer overlooks
this and builds a watchdog timer which would time out and reboot the
system if Task-H does not run for a short amount of time - the result would
be system reboots whenever Task-M comes in between Task-H and Task-L.
<p>
Here is a small program which tries to demonstrate this problem.
<pre>
#include &lt;linux/module.h&gt;
#include &lt;rtai.h&gt;
#include &lt;rtai_sched.h&gt;
#define LPT1_BASE 0x378
#define STACK_SIZE 4096
#define TIMERTICKS 100000000 /* .1 second */
#define HIGH_PRIO 0
#define MEDIUM_PRIO 1
#define LOW_PRIO 2
#define PORTB 0x61
#define PIT_CTRL 0x43
#define PIT_DATA 0x42
static RT_TASK my_task1, my_task2, my_task3;
SEM flag;
RTIME tick_period;
unsigned char c = 0;
void speaker_on(void)
{
unsigned char c;
c = inb(PORTB)|0x3;
outb(c, PORTB);
}
void speaker_off(void)
{
unsigned char c;
c = inb(PORTB)&amp;~0x3;
outb(c, PORTB);
}
void generate_tone(void)
{
/* Counter 2, low and high, mode 3, binary */
outb(0xb6, PIT_CTRL);
outb(152, PIT_DATA);
outb(10, PIT_DATA);
}
static void my_delay(unsigned int i)
{
while(i--);
}
/* Highest priority */
static void info_bus_task(int t)
{
speaker_on();
rt_sem_wait(&amp;flag);
rt_printk("info bus task got mutex...\n");
rt_sem_signal(&amp;flag);
speaker_off();
}
/* Medium Priority */
static void comm_task(int t)
{
my_delay(0xffffffff);
my_delay(0xffffffff);
my_delay(0xffffffff);
}
/* Low priority */
static void weather_task(int t)
{
rt_sem_wait(&amp;flag);
rt_sleep(30*tick_period);
rt_sem_signal(&amp;flag);
}
int init_module(void)
{
RTIME now;
//rt_typed_sem_init(&amp;flag, 1, RES_SEM);
rt_sem_init(&amp;flag, 1);
rt_set_periodic_mode();
generate_tone();
rt_task_init(&amp;my_task1, info_bus_task, 0, STACK_SIZE, HIGH_PRIO, 0, 0);
rt_task_init(&amp;my_task2, comm_task, 0, STACK_SIZE, MEDIUM_PRIO, 0, 0);
rt_task_init(&amp;my_task3, weather_task, 0, STACK_SIZE, LOW_PRIO, 0, 0);
tick_period = start_rt_timer(nano2count(TIMERTICKS));
now = rt_get_time();
rt_task_make_periodic(&amp;my_task1, now + 2*tick_period, tick_period);
rt_task_make_periodic(&amp;my_task2, now + 3*tick_period, tick_period);
rt_task_make_periodic(&amp;my_task3, now + tick_period, tick_period);
return 0;
}
void cleanup_module(void)
{
stop_rt_timer();
rt_busy_sleep(10000000);
rt_sem_delete(&amp;flag);
rt_task_delete(&amp;my_task1);
rt_task_delete(&amp;my_task2);
rt_task_delete(&amp;my_task3);
}
</pre>
The information bus, communication and weather tasks are respectively
the high, medium and low priority tasks. RTAI lets us set priorities
to tasks during rt_task_init. The weather task starts first. It grabs
a semaphore (the semaphore is initialized to 1 in rt_sem_init) and
then goes to sleep for 30 ticks (3 seconds, as each tick is 0.1 second).
The information bus task runs at the next timer tick (the second argument
to rt_task_make_periodic is the point of time at which the task is to be
started); it turns on the PC speaker and then attempts to do a `down'
operation on the semaphore and in the process, gets blocked. We expect the
weather task to complete its sleep, release the semaphore and let the
information bus task run to completion, thereby stopping the noise coming
out of the speaker. But the trouble is that before the weather task comes
out of its sleep, a medium priority `communication' task gets scheduled and
starts executing a series of busy loops (which on my Athlon XP system generates a
combined delay of about 17 seconds when compiled with -O2 - it would be better if you time the delay
loop in a userland program before you plug it into the kernel - remember, as
long as that delay loop is running, your machine will be in an unusable state -
so be careful with what you do). The operating system can't bring the weather
taks out of its sleep even after 3 seconds is over because the medium priority
task is busy executing a loop - after about 17 seconds, the communication task
would end, thereby letting the weather task continue with its execution. The
weather task perform an `up' operation on the semaphore bringing the information
bus task out of the block and letting it stop the speaker. We note that the
high priority information bus task is getting delayed by the communication task.
<p>
RTAI supports `resource semaphores' - they can be used to solve the above
problem. Had we initialized our semaphore like this:
<pre>
rt_typed_sem_init(&amp;flag, 1, RES_SEM);
</pre>
the task which originally `acquired' the semaphore (the weather task) would
have `inherited' the priority of the high priority information bus task blocked on it.
This would have resulted in the RTAI scheduler preempting the communication task
and giving control back to the weather task exactly after 3 seconds of sleep.
<h2>Acknowledgements</h2>
<p>
The webcam-servo motor setup was implemented by <b>Krishna Prasad</b>, <b>Mahesh</b> and
friends as part of a Computer Vision project; they wish to acknowledge
the influence of <b>Cort Dougan's</b> implementation of the idea on RTLinux.
RTAI comes with good documentation, and lots of example code. I would like
to thank all those people who took the pains not only to build a great system,
but also document it well.
<h2>About the Author</h2>
<p>
I have been teaching GNU/Linux and elementary Computer Science since
1997. If you are sure that you really wish to waste your time, you might
drop in on my home page <a href="http://pramode2.tripod.com">pramode2.tripod.com</a>
</body>
</html>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
I am an instructor working for IC Software in Kerala, India. I would have loved
becoming an organic chemist, but I do the second best thing possible, which is
play with Linux and teach programming!
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, Pramode C.E.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">Quick and dirty guide to debugging tcp/ip</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/dorgan.html">David Dorgan</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Quick and dirty guide to debugging tcp/ip</title>
<meta name="GENERATOR" content="amaya 5.1" />
<style type="text/css">
<!--
.header {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 24px;
font-weight: bold;
color: #999999;
}
.author {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
font-style: italic;
color: #666666;
margin-left: 25px;
}
.disclaimer {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
margin-left: 50px;
}
.cvsinfo {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
}
.body {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
margin-left: 50px;
}
-->
</style>
</head>
<body>
<p class="header">A quick and dirty guide to debugging tcp/ip</p>
<p class="author">David Dorgan.</p>
<p class="disclaimer">This is a small guide I wrote into debugging TCP/IP networks. It assumes
you are using linux, or other unix like o/s.</p>
<p></p>
<p class="body">So it's 5pm on a Friday, a user says he/she cannot connect to
$some-web-site, What do you do? There are a few paths, often internal and
external sites will require a different approach.</p>
<p></p>
<p class="body">Some things won't change, think if it this way, if layer 1 (physical)
isn't working, everything on top of that isn't going to work, it's a good
idea to use a number of tools, like telnet, ping, traceroute, tracepath
etc... to see where the problem is, and if you can, what layer it's ok. Say
if you can ping and traceroute fine to a host, you can get to port 25, but
not port 80, then the chances are it's just their webserver dying. Say you
can't get past your local gateway, but you can ping you local gateway, it
could be the case that it's not forwarding, it's a firewall configuration
issue etc...</p>
<p></p>
<p class="body">Try and telnet to thesite.com on port 80, to see if you can connect, if
you get connection refused and you don't have any firewalls or proxys
blocking outbound communication, the chances are they are having some sort of
service outage. If it just stays there for a while and then says 'cannot
connect' then continue.</p>
<p class="body">Try and ping the remote side, although this is very useful, some places do
block ICMP (they must be under the impression that while creating tcp/ip, for
the first six days most of the work was done, and they had nothing to do on
Sunday, so they invented ICMP as a joke), so you could try a traceroute, once
again this could be blocked, but it'll generally give you a picture of where
the problem is. At this point, look at see where it stops, you should see
your local gateway and maybe some internal routers of gateway devices, after
this you should see it going through ISP networks, if you don't see your ISP
anywhere and it stops on the first few hops, it could be a problem with the
link to your ISP, if it shows your ISP and then shows an outage just after
your ISP's name, maybe the ISP has lost the link to one of their upstreams
and the old paths are still valid so packets are being stopped there. Finally
you may see it go all the way to the other side, and finish totally, or stop
on somecompany-gw.customer.isp.net, in which case the other side may be
blocking inbound ICMP.</p>
<p class="body">If they can't seem to connect to anything, ask them to try with an IP, if
this works, get them to check their DNS settings.</p>
<p></p>
<p class="body">Some common traits of certain events.</p>
<p></p>
<p class="body">A service dying but the network being fine: If you can ping and traceroute
fine, and you can connect to other open ports, say the machine does mail and
remote access, if you can get to port 22 (ssh) fine but not port 25 (smtp)
there could be a problem with the MTA only.</p>
<p class="body">A firewall blocking a port: This doesn't work so well when routers or
firewalls have a 'deny all' by default, but most people don't do that. Let's
say you can't get to port 25 on this machine, when you telnet, it just times
out, but you know it's a mailserver, try to telnet to a few ports, just
random high number ports, like 8274 or 9274 and see if you get connection
refused. If you get connection refused, the chances are the firewall is just
blocking port 25 due to your IP, because the machine responded that you
couldn't get on those ports.</p>
<p class="body">The link to your ISP is dead: Try and traceroute to anywhere, and you will
see that the last hop that doesn't time out is an internal one from your
company, and that you never see anything with link-whatever.isp.net.</p>
<p class="body">The link is gone on the other side: In this case, maybe you know they
don't block traceroute packets, so when you do traceroute, it goes through
your isp, to a carrier, to their isp and then stops on what is normally their
ISP's link.</p>
<p class="body">Your ISP is having a routing issue: This often happens with some providers
*ahem*, I have accounts on a few machines, based in physically different
locations and using different providers, so if I can't get to a resource I
want, ill try and traceroute it from a machine hanging straight off LINX and
a few just off some US ISP's, if they all seem to work from there, and a
traceroute from you shows timeouts or unusually high latency in say
london.isp.net, then their links to london maybe overused or having
issues.</p>
<p class="body">It's taking about two minutes to login to a machine: When you do login,
type w or who, and check to see if it says you are coming from an IP or
hostname? It shouldn't say hostname, basically it's waiting that long on DNS,
it should use an internal DNS server that will reply quickly, or else you
should use reverse lookups for IP addresses.</p>
<p class="body">Somebody is complaining they can't connect to a service, you try
a manual connection from an outside host and it doesn't work. Then go onto the machine
and try and telnet to the port or do an netstat -an | grep LISTEN and look for the port
number it should be listening on. If it is there, it could be filtered somewhere along the
path, or even at the local host. If it isn't listen, then doing an fstat or lsof and
and grepping for the process name may show IPv4 or internet entry, showing
the ip address and host it's listening on.</p>
<p></p>
<p></p>
<p class="cvsinfo">$Id: debugging-tcpip.html,v 1.5 2003/09/18 18:33:47 davidd Exp $</p>
</body>
</html>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
David has been a very productive writer and plans to contribute more of his
work in the future.
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, David Dorgan.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">A quick and Dirty guide to extending snmp</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/dorgan.html">David Dorgan</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<html>
<head>
<title>A quick and Dirty guide to extending snmp</title>
<style type="text/css">
<!--
.header {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 24px;
font-weight: bold;
color: #999999;
}
.author {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
font-style: italic;
color: #666666;
margin-left: 25px;
}
.disclaimer {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
margin-left: 50px;
}
.cvsinfo {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
}
.body {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
margin-left: 50px;
}
-->
</style>
</head>
<body>
<table border="0" cellpadding="3" cellspacing="0" width="100%"
bgcolor="#FFFFFF">
<tbody>
<tr>
<td><p>Monitoring and Graphing Applications with SNMP and MRTG.<br />
<br />
There are two basic sections in this article, first will be
checking<br />
services or processes via net-snmp.<br />
<br />
First off download net-snmp from net-snmp.org, a simple<br />
./configure ; make ; make install should do the trick in most
cases.<br />
After this you should run sudo snmpconf, to create your snmpd.conf<br
/>
file, which will contain your community names, location etc...<br />
Then with the basic configuration you could start the snmpd with<br />
sudo snmpd, or sudo snmpd -r which enables net-snmp to drop most<br />
privileges just after startup.<br />
<br />
In this default setting, with a default configuration,<br />
you could do something like snmpwalk -v 1 -c public localhost , to
see<br />
some of the built-in settings. Now to get to the interesting
section,<br />
let’s say you want to monitor an application you just wrote...<br />
let’s say you want to check if port 25 is up, via snmp....<br />
You could write a simple python application[0], which returns 0<br />
for a success, or 1 for a failure...<br />
<br />
(In real life you would probably just do this from a remote host, but
this<br />
is just a simple example which can be expanded to your
application).<br />
<br />
Now to monitor this event, in your /etc/snmpd.conf add a line
like...<br />
exec 1.3.6.1.4.1.5000.100 check-smtp /software/snmp/check-smtp.py<br
/>
<br />
A oversimplified explanation of the number would be,<br />
1.3.6.1.4.1 means enterprise, 5000 would be your organisations MIB<br
/>
number, and 100 would be the specific OID. For more information on
getting<br />
an organisation private enterprise number, you should see<br />
http://www.iana.org/cgi-bin/enterprise.pl<br />
<br />
Now if you type snmpwalk -v 1 -c public localhost
1.3.6.1.4.1.5000.100<br />
you will see not just the reply, but all objects within the OID.<br />
If you wanted to be specific (which you may need to do for snmp
managers<br />
or mrtg...you would have something like snmpwalk -v 1 -c public
localhost 1.3.6.1.4.1.5000.100.101.1<br />
<br />
Or graph something (anything) on a remote machine with snmp and
mrtg?<br />
<br />
Now let’s say, you wanted a simple mrtg graph, which only checked
for the amount<br />
of threads in a mysql database, which while useful, is once again a
pretty<br />
simple example, let’s say you didn’t mind spawning a shell and
executing a command,<br />
you might do something like mysqladmin status | awk {’print $4’}
...<br />
which is fairly system unfriendly, but there isn’t much point
presenting a robust<br />
c application in this case. Now in /etc/snmpd.conf add<br />
<br />
exec 1.3.6.1.4.1.5000.101 mysql-thread-load
/software/snmp/mysql-thread-load.sh<br />
<br />
<br />
inside the file have<br />
#!/bin/sh<br />
mysqladmin status | awk {’print $4’}<br />
<br />
and make sure it’s executable by the calling process.<br />
<br />
Here is a sample partial mrtg config[1].<br />
<br />
The reason in Target that you have specified the number twice,
breaking it up with an &amp; sign,<br />
is that mrtg generally expects two inputs, one for incoming and one
for outgoing, this way<br />
it just uses the same reply for both. Of course you could monitor
something like mysql threads,<br />
and load average, and they could be graphed in the same picture,
which can be interesting<br />
for correlation between application and system load.<br />
<br />
<br />
<br />
[0]:<br />
import socket<br />
import time<br />
<br />
HOST = ’localhost’<br />
PORT = 25<br />
<br />
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br />
try:<br />
s.connect((HOST, PORT))<br />
print ’0’<br />
except socket.error:<br />
print ’1’;<br />
<br />
<br />
[1]:<br />
Target[mysqlconnections]:
1.3.6.1.4.1.5000.101.101.1&amp;1.3.6.1.4.1.5000.101.101.1:public@hostname<br
/>
options[mysqlconnections]:
nobanner,absolute,gauge,growright,nopercent<br />
Title[mysqlconnections]:Mysql Threads<br />
PageTop[mysqlconnections]: &lt;h1&gt;Mysql Threads&lt;/h1&gt;<br />
MaxBytes[mysqlconnections]: 1000<br />
YLegend[mysqlconnections]: connections<br />
ShortLegend[mysqlconnections]: connections<br />
LegendI[mysqlconnections]: connections:<br />
LegendO[mysqlconnections]:<br />
Legend1[mysqlconnections]: connections<br />
Legend2[mysqlconnections]:<br />
Step[mysqlconnections]: 12<br />
<br />
<br />
</p>
</td>
<td></td>
</tr>
</tbody>
</table>
<p>$Id: dirty-snmp.html,v 1.4 2003/08/30 15:00:35 davidd Exp $ </p>
</body>
</html>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
David has been a very productive writer and plans to contribute more of his
work in the future.
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, David Dorgan.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">The state of software security</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/dorgan.html">David Dorgan</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>The state of software security.</title>
<meta name="GENERATOR" content="amaya 7.2, see http://www.w3.org/Amaya/" />
<style type="text/css">
<!--
.header {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 24px;
font-weight: bold;
color: #999999;
}
.author {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
font-style: italic;
color: #666666;
margin-left: 25px;
}
.disclaimer {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
margin-left: 50px;
}
.cvsinfo {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
}
.body {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
margin-left: 50px;
}
-->
</style>
</head>
<body>
<p class="header">The state of software security.</p>
<p class="author">David Dorgan.</p>
<p class="disclaimer">Note, this is just a alpha document , I am going to work more on this.</p>
<p class="body">Computer security today is appalling. It is awful, there are worms all the
time, there are ones to attack your email, maybe it's an irc network, maybe
it's just a flood of traffic, the situation is getting out of control, and
I've not seen any 'security' company help, in fact, they are making things
worse, 'how much worse?' allot worse, there are lots of hosts infected right
now, and when an owner gets pissed, he hits you. The openssh bug recently was
first presented at defcon of this year, and was supposed to be known within &#8217;some circles&#8217; for over a year.
I wonder how many
of those exist right now?.</p>
<p></p>
<p></p>
<p class="body">I am fast becoming disillusioned with software security. It seems like an
uphill battle which just isn't being won. Every company offers the silver
bullet, and most users accept that. I'll take an example, recently there have
been some virus outbreaks, now allot of machines got infected, and the worm
pinged allot of hosts before it infected, in fact it would only try and
infect those who replied. This caused a DoS attack on the clients site very
often, it seems to have started on the subnet you are on, some if some guy
had a laptop and popped behind a 192.168.x.x network, it would try and infect
the whole network. The patch site that MS run was very slow due to the
demand, 'but what about anti virus software?' Personally I think if the ISP
detected this worm on a customers network it should have disconnected their
network and then fined the user for wasting their time.</p>
<p></p>
<p class="body">There are some problems with antivirus software,</p>
<ul>
<li class="body">It solves yesterdays problem, NOT todays.</li>
<li class="body">If you are up to date, it won't protect from a custom virus for you,
which anybody could make VERY easily.</li>
<li class="body">It's a workaround, it does not go NEAR the root cause.</li>
</ul>
<p class="body">Now after that recent scare, some 'internet patch' crap did the rounds,
and some IDIOTS actually clicked on the .exe file, of course they can plead
ignorance. But if I get a car and smash it into somebody, I can't plead
ignorance, there is NO liability put on the end user in computing, there is
NO liability on software quality put on the vendor. In fact, if you want to
think about how careless vendors are, visit this page on <a
href="http://www.pivx.com/larholm/unpatched/">Unpatched IE security
holes</a>. </p>
<p></p>
<p class="body">Allot of this could be stopped by a tiny amount of clue, in programming,
WHY USE STRCPY if you are using C, if you are teaching C in college, DON'T
LET ANYBODY USE THEM! Fail anybody who does use them. In the testing phase of
code, fail anybody for using these, if they are silly enough to use strcpy
for input from a user for example, imagine the possible amount of race
conditions, format string overflows etc...</p>
<p class="body">For the end user, do not click on executable files, just don't, don't ask
why, who cares who it's seemed to have been sent from, don't execute it, or
pif files, or bat files, or scr files etc. Why use word documents? HTML is
cross platform, looks great etc...</p>
<p></p>
<p class="body">It's going to get allot worse before it gets better, imagine 1000 of those
sobig worms around, not just one. Imagine lots of more infected flying around
and stupid software replying to each one, to mailing lists with 100,000
people on them. The future of secure computing isn't coming from vendors such
as symantec, that's one thing I do know, and I really believe this after some
really stupid statements that some of their 'leaders' have come out with.</p>
<p></p>
<p class="cvsinfo">$Id: security.html,v 1.7 2003/10/03 17:34:27 davidd Exp $</p>
</body>
</html>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
David has been a very productive writer and plans to contribute more of his
work in the future.
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, David Dorgan.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">SSH with keys</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/dorgan.html">David Dorgan</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html>
<head>
<title></title>
<style type="text/css">
<!--
.header {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 24px;
font-weight: bold;
color: #999999;
}
.author {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
font-style: italic;
color: #666666;
margin-left: 25px;
}
.disclaimer {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
margin-left: 50px;
}
.cvsinfo {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
}
.body {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
margin-left: 50px;
}
-->
</style>
</head>
<body>
&nbsp;
<table border="0" cellpadding="3" cellspacing="0" width="100%"
bgcolor="#FFFFFF">
<tbody>
<tr>
<td><p>It has come to my attention that a lot of people like using ssh,
most do not use keys, some do. What struck me is that most of the
people who do use keys don't use passphrases with them, when I
asked some people why not, they said they didn't like typing their
password each time, this isn't the case. <br />
<br />
<br />
Some background, let's say you want to tell somebody your password
for an account on a machine, but you don't know who is listening,
your only method of communication is cleartext communication over an
insecure channel. Then what to do you?<br />
Public key cryptography is the answer, you can send your public key
to anybody, you just keep your private key to yourself.<br />
<br />
To create a key, simply run ssh-keygen, with the options<br />
ssh-keygen -t dsa.<br />
You should be prompted for where to save your keys, e.g.
/home/user/.ssh/id_dsa and /home/user/.ssh/id_dsa.pub<br />
Then you will be prompted for a password, public keep systems are
great for security, however they are only as good as their weakest
link, don't let your passphrase be the weakest link.<br />
<br />
You should never *EVER* put your private key on a server, you should
never put it on a disk.<br />
Personally I just keep it on my laptop, nowhere else, ever. Then put
your public key on the remote hosts in the file
/home/user/.ssh/authorized_keys .<br />
<br />
Some people have their servers setup to only accept RSA key
authentication, which isn't a bad idea.<br />
<br />
Now, people do complain about having to enter their passphrase each
time, this isn't *really* an issue. Personally I start X with a
script in rc.local.<br />
<br />
$ cat /etc/rc.local<br />
ssh-agent xdm<br />
Now once inside X as your user, type ssh-add, enter your passphrase,
now each xterm you open, you can type ssh server, and you won't be
prompted for a password.<br />
One point to note on this, be *SURE* to lock your workstation while
away, even for a few seconds.<br />
</p>
</td>
</tr>
</tbody>
</table>
<p>$Id: ssh-with-keys.html,v 1.4 2003/08/30 15:00:35 davidd Exp $ </p>
</body>
</html>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
David has been a very productive writer and plans to contribute more of his
work in the future.
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, David Dorgan.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">Using Screen</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/dorgan.html">David Dorgan</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Using Screen</title>
<meta name="GENERATOR" content="amaya 7.2, see http://www.w3.org/Amaya/" />
<style type="text/css">
<!--
.header {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 24px;
font-weight: bold;
color: #999999;
}
.author {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
font-style: italic;
color: #666666;
margin-left: 25px;
}
.disclaimer {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
margin-left: 50px;
}
.cvsinfo {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
color: #CCCCCC;
}
.body {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 10px;
margin-left: 50px;
}
-->
</style>
</head>
<body>
<p class="header">Useful features of screen</p>
<p class="author">David Dorgan.</p>
<p class="disclaimer">This is a very basic introduction to some of useful
features of screen.</p>
<p></p>
<p class="body">I learned to use screen after I saw what it could do, it has
some very good uses, basically screen is a screen manager with terminal
emulation. The best way to see how it works and how it could be useful for
you, is to use it. I'll give you one reason why I use it, I use irc allot, I
don't mind idling and letting my client stay on, or sometimes I used to leave
it on and then have to kill the connection if nickserv was available on that
server, but with screen I login from a server I use, I just login and
'attach' the session, and I can detach it and reattach from any machine I
like, because the virtual screen is always there.</p>
<p></p>
<p class="body">For a really basic example, install screen, then run screen
by typing <em>screen,</em>once inside this type <em>vim myfile.c,</em>now
type <code>Ctrl A</code>, and then hit the <code>d</code>key. Now you should
be back at your normal shell, now type screen -list , and you will see there
is one screen session belong to you, now type <em>screen -x</em>to reattach
this session. Now you will see the same session, now if you have an account
on a remote host, maybe login and do the same with IRC, then detach and
reattach, and you will see all the new messages too, and you can do this with
any terminate application from anywhere, useful isn't it?</p>
<p></p>
<p class="body">Now just so that you know, you can have a few sessions
running and one easy way of re-attaching would be do to a <em>screen
-list</em> and then s<em>creen -R $screen_number .</em>There are betters ways
to handle this, but for more information on that in the screen man page.</p>
<p></p>
<p class="body">Now say you want more than one shell per screen session,
start screen, then type <em>echo 'this is number one' ,</em>then type
<code>Ctrl-A</code>and <code>n,</code> now you should see another new window,
now hit <code>ctrl-a</code> and<code>0,</code>you should now be back to your
first terminal, you can create a number of these, to destroy one just type
<code>ctrl-a</code> and <code>k, ctrl-a and p will bring you to the pervious
window and ctrl-a n will bring you to the next. For help type ctrl-a ?
.</code></p>
<p class="body">There are many other things you can do, just read the man
page.</p>
<p class="cvsinfo">$Id: using-screen.html,v 1.3 2003/08/30 15:00:35 davidd
Exp $</p>
</body>
</html>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
David has been a very productive writer and plans to contribute more of his
work in the future.
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, David Dorgan.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">Linux as a RTOS</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/bhargava.html">Nikhil Bhargava</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<HTML>
<HEAD>
<TITLE>Real time linux</TITLE>
</HEAD>
<BODY>
<Font Face="TIMES NEW ROMAN, ARIEL" size=5 color=BLACK>
<CENTER><B>
Linux as a RTOS
</B></CENTER>
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=3 color=BLACK>
<LEFT>
A real-time operating system (RTOS) [1] is an operating system capable of guaranteeing timing requirements of the processes under its control. While a time-sharing OS like UNIX strives to provide good average performance, for a RTOS, correct timing is the key feature. Throughput [2] is of secondary concern. In order to deliver the tight worst-case timing performance needed by hard real-time, the RTOS needs to be simple, small, predictable, and optimized to minimize the worst-case performance.
Linux operating system which started as a student project by Linus Travaldo gained momentum.in in late 80s is now a complete operating system meeting requirements of nearly all type of users. Further large group of developers are adding features to the core kernel as well as KLM (kernel loadable modules). However indefinite response time, treatment of interrupts, scheduling policy and timer granularity are some of the features of Linux which makes it unsuitable in embedded world where a definite response time is a must. Several techniques and patches are available to customize and modify bare Linux kernel to be acceptable as a hard real time operating system. This article discusses these issues.
</LEFT>
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=4 color=BLACK>
<LEFT><B>
1.1 Unsuitability of Linux for Hard Real Time Applications
</B></LEFT>
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=3 color=BLACK>
The following features make Linux infeasible to be used to run hard real-time applications:
1. Unpredictable scheduling - depends on system load;
2. Coarse timer resolution (10 ms);
3. Non-preemptible kernel;
4. Disabling of interrupts used for coarse-grained synchronization;
5. Use of virtual memory;
6. Reordering of requests for efficiency (e.g. for disk I/O).
Moreover, Linux processes are heavyweight processes, and it can take several hundred microseconds to finish a context switch, and thus make it impossible to schedule a task to poll a sensor every 100 microseconds. Another disadvantage of Linux is that it uses process-based model instead of thread model and signals tend to get lost during the execution of processes.
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=4 color=BLACK>
<LEFT><B>
1.2 Basic Real Time Operating System Implementation Approaches
</B></LEFT>
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=3 color=BLACK>
<LEFT>
In order to facilitate the implementation of RTOS, POSIX standard has defined RTOS related specifications. POSIX.1b-1993 standard specified some real-time features in UNIX. The standard defined prioritized scheduling, locking of user memory pages in memory, real-time signals, improved IPC and timers, and a number of other features. Linux partially supports the POSIX.1b standard. However, POSIX.1b compatibility only permits certain kinds of soft real-time processing in Linux.
<BR><BR>
Generally there are three ways to implement a RTOS.
<BR><BR>
<B>1. Microkernel Approach:</B>
An example is the QNX[4] which only implements process scheduling, interprocess communication, low-level network communication, and interrupt dispatching. All other services, such as device drivers and file systems, are implemented as user processes. So the kernel is very small (7 KB of code) and fast. Comparing with monolithic kernel, it has some advantages. Debugging user processes is easier than debugging kernel components. If user processes are executed in separate address spaces, memory management errors in different modules are isolated. Another advantage is scalability. A QNX system can be scaled down to 100K to fit in the ROM, or expanded to a full-featured multi-machine development environment. Porting and maintenance is also easier. In addition, a real-time user process can preempt a device driver, which is not the case in monolithic kernels.
<BR><BR>
However, performance becomes a weak point since microkernel architecture places heavy load on interprocess communication and context switching. Microkernels only provide simple services directly. Therefore, more system calls have to be performed in a microkernel system than in a monolithic one to accomplish the same task. it is most likely for performance reasons that monolithic kernels are still prospering.
<BR><BR>
<B>2. Monolithic Approach:</B> One example of a monolithic system is VxWorks.[7] VxWorks is a proprietary RTOS geared towards host/target approach. A UNIX host is used for software development and for running non-real-time parts of an application. The VxWorks kernel called wind runs real-time tasks on the target computer. The machines communicate using TCP/IP networking. In VxWorks, the kernel and tasks run in one address space. This allows task switching to be very fast and eliminates the need for system call traps. A run-time linker allows dynamic loading of both tasks and system modules. This feature makes for scalability. An interactive shell with C-like syntax can be used to examine and modify variables, evaluate expressions, call functions, and perform simple debugging. These features encourage experimentation and make development somewhat easier. However, they also make the system more fragile as errors in one module can easily affect others.
<BR><BR>
<b>3. Decoupled Approach:</b> Instead of "making a general purpose operating system kind-of-realtime"(IRIX)[6] and "keeping adding nonreal-time features to a real-time operating system"(VxWorks),[7] the original Real-Time Linux designers took another alternative. RTLinux[5] decouples the real-time and non-real-time systems. This mechanism makes the real-time process simple, fast, predictable and optimized to minimize worst-case performance. In order to support non-real-time applications at the same time, the general purpose Linux is run as the lowest priority thread.
</LEFT>
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=4 color=BLACK>
<LEFT><b>
1.4 Conclusions
</B></LEFT>
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=3 color=BLACK>
<LEFT>
Linux is easily the fastest growing operating systems in the embedded world. Its low cost, abundant features and openness make Linux a fertile ground for creativity. Many companies have made tailor made modifications to the kernel and or introduced new techniques to give a real time look and feel to Linux. Linux kernel developers have realized this fact that bare Linux kernel cannot give real time performance which is like oxygen to any embedded real life system. Hence in the new release of kernel version 2.6 has enhanced real-time performance, easier porting to new computers, support for large memory models, support for microcontrollers, and an improved I/O system. Linux 2.6 has been enhanced to provide support across the spectrum of needs of embedded systems from small wrist bands to large switches. As its importance grows, we can expect Linux to become the platform where future progress happens first.
</LEFT>
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=4 color=BLACK>
<LEFT><b>
1.5 References
</b></LEFT>
</FONT>
<BR><BR>
<Font Face="TIMES NEW ROMAN, ARIEL" size=3 color=BLACK>
<LEFT>
[1] Real time systems by KG SHIN and C.M. Krishna, 1st Edition, The McGraw-Hill Companies, Inc., chapter 2.<Br>
[2] Operating System Concepts by Avi Silberschatz (Author), Greg Gagne (Author), Peter Baer Galvin (Author)<BR>
[3] http://www.embedded-linux.com <BR>
[4] QNX company website: http://www.qnx.com <BR>
[5] http://www.rtlinux.org <BR>
[6] SGI Company website: http://www.sgi.com/software <BR>
[7] Wind-River Company website: http://www.windriver.com. <BR>
[8] http://www.linuxdevices.com/articles/AT7751365763.html <BR>
</LEFT>
</font>
</BODY>
</HTML>
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
<font face="Ariel" size=3 color=BLACK>
I am <A HREF="http://www.geocities.com/nikhil_bhargav">Nikhil Bhargava</A> from Delhi, India. I am a computer engineer and curently working in <A HREF="http://www.cdot.com">CDOT</A>, India for past one year.
</FONT>
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, Nikhil Bhargava.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
<TABLE BORDER><TR><TD WIDTH="200">
<A HREF="http://www.linuxgazette.com/">
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
WIDTH="200" HEIGHT="41" border="0"></A>
<BR CLEAR="all">
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
</TD><TD WIDTH="380">
<CENTER>
<BIG><BIG><STRONG><FONT COLOR="maroon">Csound: An Interview with Dr. Richard Boulanger</FONT></STRONG></BIG></BIG>
<BR>
<STRONG>By <A HREF="../authors/baxter.html">Michael Baxter</A></STRONG>
</CENTER>
</TD></TR>
</TABLE>
<P>
<!-- END header -->
<p>
Dr. Boulanger has been associated with Csound for a long time, and is
the editor of The Csound Book (see resources), an excellent resource
consisting of multiple contributions from the Csound community for
learning and using Csound. In a chat with Dr. Boulanger,
we provide perspective on one of the oldest C-based software sound
synthesis environments. This in-depth interview complements Dave
Phillips' recent article (see May 2003 LJ, page 80) about the newest
Linux softsynth environments.
<p>
Q: Dr. Boulanger, thank-you for your time. Four years ago _Linux
Journal_ ran an article by David Phillips on Csound on Linux. Could
you describe some of the advances to Csound since that time?
<p>
A: As you know, Michael, Csound is arguably the most powerful
cross-platform software synthesis and signal processing system
available today. It's incredible, it continues to grow and improve,
and most importantly, it's free! Although many commercial applications
such as Max/MSP, PD, SuperCollider, Tassman, and Reaktor are getting
closer and closer to Csound's programability, power and functionality,
nothing comes close - especially given all the platforms and operating
systems upon which one can run the very same Csound orchestras,
scores, and instruments.
<p>
And you are right, I have been composing with, teaching with, and
writing about this incredibly powerful and versitile program for over
25 years now. I started studying at the MIT Experimental Music
Studion in 1979 with Barry Vercoe. There I was doing sound design and
composition using Barry's music11 program - essentially Csound for the
PDP11 minicomputer. That very first music11 composition of mine -
"Trapped in Convert" has been presented in concerts all over the world
- including Alice Tully Hall in New York - quite a big deal for a then
budding young composer! When I returned to the MIT Media Lab in 1986
with my Computer Music Ph.D. in hand, I worked with Barry betatesting
his new language - Csound. We would use "Trapped" to make sure that
all the opcodes were working correctly.
<p>
In fact, the version of "Trapped in Convert" that people render and
tweek today was the very first Csound piece. And what is so important to
me is that this very same piece
(http://csounds.com/compositions/colleaguezip/Trapped.zip) can be
rendered and studied today using a version of Csound that runs on
virtually any computer. Back in 1979, it took hours to render each sound
and gesture, days to render each phrase and section, and weeks to
render the entire four and a half minute piece - at 24K! Today, at
44.1K, "Trapped in Convert" renders in realtime on virtually any PC.
<p>
For me, the ability to preserve the history of computer music
composition and sound design is extremely important. Much of the music
I composed using sequencers, synthesizers and MIDI equipment during the
80's and 90's has been retired and lost when the gear was sold,
broke-down, or the computers running early sequencers and sound editers
were retired to the basement. Getting rid of an old computer usually
meant tossing out your music too. Yet, the very fact that I can still
render, "tweek," and teach with my old Csound pieces is a testament to
Csound's greatness. For me at least, Csound has proven to be
future-proof. In fact, since Csound is a direct decendent of the MusicN
languages developed by Max Mathews at Bell Labs in the late 50's, the
entire history of computer music research is preserved in this program.
Many of the classic pieces and classic instrument design catalogs, by
Risset for instance, have been totally reconstructed in Csound and can
be rendered, studied, and modified to this day.
<p>
Since Dave Phillips' wonderful Linux Journal article on Csound, there
have been a number of important milestones. Several Csound Books have
been published - The Csound Book (MIT Press), Virtual Sound (ConTempo),
and Cooking with Csound (AR Editions). The Csound Instrument Catalog
has been released with thousands of models to study and modify. The
quarterly Csound Ezine has been a regular source of inspiration and
undertanding. Extensive Csound tutorials have been featured in Keyboard
and Electronic Musician Magazines. In addition to The Csound mailing
list, two new Csound mailing lists have been started - the csoundTekno
list, and the csoundDeveloper's list. The international Csound
community of Csound teachers, users, and developers has really grown and
their cSounds have gone mainstream - featured in major Hollywood films
(Traffic, Black Hawk Down, Narc), and an number of Computer Games. Dave
Phillips himself has finished a wonderful book, "The Book of Linux Music
and Sound" that features some wonderful stuff on Csound and related
applications and utilities that is a real help for newcomers to the
Linux audio world.
<p>
In the last four years, there have been some incredibly developments to
Csound by the key platform developers and maintainers. Barry Vercoe
continues to develop proprietary versions of Extended Csound for embebed
systems and Analog Devices DSP chips. Matt Ingalls continues to push the
Macintosh versions of Csound in wonderful ways. His MacCsound has user
defined GUI Widgets built into the launcher, support for instruments as
plugins, and super clean MIDI (at last!). Even cooler, his csound~
external for Max/MSP and PD essentially embed the entire Csound language
into the Max/MSP/Jitter and PD/GEM graphical programming environments
and thus add incredibly interactivity, estensive algorithmic
capabilities, super MIDI, and multichannel/low-latency ASIO support to
Csound on the Mac. Sound Designers and Composers such as Joo Won Park,
Sean Meagher, and Takeyoshi Mori have developed wonderful real-time
GUI-based applications such as CsoundMax, CsoundFX, and CsoundMixer.
<p>
Michael Gogins has been busy with CsoundVST, a version of Csound that
runs as a VST plugin in Cubase and Nuendo for the PC. Most recently he
completely embedded Csound into his algorithmic composition language
SilenceVST that can run stand-alone or be hosted by the PC versions of
Cubase or Nuendo. He has also done some extensive collaboration with
Matt Ingalls to define a preliminary Csound API.
<p>
Gabriel Maldonado's CsoundAV for Windows has ASIO support and adds
hundreds of openGL and GUI opcodes to the language. It is incredible to
make audio instruments that communicate with GUI instruments all from
the same Csound orchestra and all with the same exact syntax! A number
of Csound's top sound designers such as Luca Pavan, Josep Comajuncosas,
Oeyvind Brandtsegg, and Alessandro Petrolati have developed an arsenal
of incredible GUI-based real-time applications, instrument, and effect
collections.
<p>
Somewhat controversial and radically new and expanded Linux versions of
Csound were developed by Maurizio Umberto Puxeddu (iCsound), and are
currently under extensive development by Istvan Varga.
<p>
And behind the scenes, John ffitch, with some help and support of
Richard Dobson, has been maintaining, improving, and extending Canonical
Csound FOR ALL PLATFORMS! In fact, we are currently in an "opcode
freeze" (no new opcodes) so that he can totally revise the core and
support many of the innovations introduced by Varga, Ingalls, Gogins,
and Maldonado while adding new levels of clarity and new functionality -
such as plugin support, ASIO support, a new parser and much much more.
(His most recent TODO list is posted in the news at cSounds.com.) For
one thing, when ffitch is done, it should be easier for users to add
opcodes of their own without having to recompile the entire program.
<p>
Of special note for all platforms is Steven Yi's inspired and inspiring
"Blue" and "Patterns" composing and sound design environment. And also,
the wonderful Csound FLTK signal processing and sound design front end
"Cecilia" that has come to life in the windows version by Bill Beck and
the improved Linux and osX versions by Stephan Bourgeois and
Hans-Christoph Steiner.
<p>
I have forgotten to mention a ton of things like all the great new
Csound editors and applets and all those free VST and DirectX plugins
based on Csound Code - like he Delay Lama VST plugin and Dobson's new
PVFX for Cakewalk's Project 5. What can I say? In four years, with ALL
these incredible students, composers, teachers, developers on ALL thise
platforms, with all these musical dreams and perspectives, what did you
expect? All the new versions are great. All the new opcodes are great.
All the new capabilities are great but honestly, I am thrilled by ALL
the new Csound Music and the ways that Csound is being used by
musicians. This is the big leap forward for Csound.
<p>
But wait one minute, have I left out all the dirt? All the name
calling? All the childish bickering and mudsling? All the "my version
is better than your version" stuff that you would expect from intensely
competitive, young and arrogant musical programmers? Well, there has
been four years of that too! (And you in the Linux community might be
proud to know that most of the mud was over Linux versions of Csound!>
And what has the result of those efforts been, you might ask? A lot of
wasted time. A lot of deep wounds that may never heal. A lot of better
versions of Csound - especially for Linux. And of course, a lot of
casualties. Hundreds of newcomers and oldtimer have dropped out of the
Csound community and abandoned working with Csound entirely because of
all the negativity associated with it. I can't blame them. I'm getting
a little tired myself of trying to teach and play music in a war zone.
<p>
(At csounds.com you can find yesterday and today's Csound News with
links to the various tools and utilities that have been developed in the
past 4 years. Also, you will find links to the Csound Mailing List
archive where you can re-live the "War over the Future of Csound" and
the vicious and childish debates over "Who Deserves to Be the Supreme
Ruler of Csound.")
<p>
Q: My impression would be that the rising computational power of
commodity PC platforms in recent years has benefited Csound more than
the declining cost of DSP microprocessors. Would you agree, and can
you comment?
<p>
A: For several years, I worked with Barry Vercoe and a team of
developers (including Barry's son Scotty - I was Scotty's Csound
Teacher!) on a project at Analog Devices to develop and commercialize
a version of Csound built around their SHARC DSP chip. At that time,
this was the way to go. For some applications it still is. Barry, in
fact, continues to develop and advance such a system. And although it
was a thrill to be part of that team and make a version of Csound that
was fast, clean, and commercially oriented, I prefer Native Csound,
public Csound, Canonical Csound. At Analog Devicest, we innovated
like crazy - streamlining and restucturing the language to make it
much more efficient, but all this cost some of the generality. We
would come up with the best way to do things. What I love about
Canonical Public Csound is that there are so many ways of working. So
many of the developers, sound designers, teachers, composers have
added features that we didn't have at Analog Devices. Moreover, their
unique work and original designs, showed me how to a new way of doing
things and helped me understand things. Even though we had built an
amazing system there, a commercially viable version of Csound, I still
preferred working with John ffitch, Matt Ingalls, Michael Gogins,
Richard Dobson, and Gabriel Maldonado to add and improve a version of
Csound that everyone could use for free.
<p>
Four years ago, real-time MIDI control did work in Csound and realtime
audio was supported too, but neither worked well. At that time, no
version of Csound worked as cleanly and straightforwardly as most
commercial hardware and software tools. (In fact, I left most of the
MIDI and Real-time Audio chapters out of "The Csound Book" because those
aspect of the language were in such flux at the time that most of what
we were writing was about all the little kluges and tricks you would
have to use to get real-time MIDI and Real-Time Audio to work.) Today,
with improved MIDI and Audio in ALL versions of Csound, with inexpensive
Multi-channel USB and FireWire Interfaces, with fast PC/Macintosh
laptops and cheap/fast desktops, we finally have everything we need for
Csound to take the stage alongside any commercial hardware or software
synthesizer - and you are starting to see a lot of this - a lot of
people performing with Csound and doing interactive Sound Design,
Phrase-Sampling, etc.
<p>
Q: One of the issues confronting a new user these days is that Csound
continues to have a batch-oriented syntax. While front ends help, this
syntax is sometimes a step backward for someone already used to
object-oriented languages who'd really like use Csound directly. Could
you describe the feeling within the Csound community about changing or
not changing Csound's syntax?
<p>
A: I don't speak for the community. It is wonderfully rich and
diverse, and that means that there are way too many desires, demands,
expecations, biases, and prejudices. Then there are all the platform
and OS wars to deal with too. As you might well imagine, the hackers
want it one way; the composers want it another; performers, producers,
sound designers want it yet another. Csound is what it is. It is
easy to learn, it is easy to expand, it is easy to personalize, and it
is a wonderful way to learn about synthesis, and signal processing.
<p>
I want Csound to work well. So that nothing is lost, I want it to be
100% backward compatible. At the same time, I want the real-time MIDI
and real-time Audio to be comparable to that supported by any of today's
commercial applications. On each hardware platform and under each
operating system, I want to see Csound integrate seemlessly with other
MIDI and audio applications. Today and into the distant future, I want
Csound to be a free, powerful, expandible, and generally useful tool for
everyone.
<p>
I want Csound to work as a plug-in/audio-unit, and I want Csound
instruments to compile as plugins and audio-units. (We are getting close
to this.) I can tell you that John ffitch and other key develors are
currently working to make the core more solid and transparent and to
make it easier to communicate with the core. There is work on the API
that will allow users to simply plug in shareware/freeware/proprietary
opcodes and libraries. We are very close to that even now.
<p>
For new users, there is plenty of graphically-oriented, user-friendly
"Instant Csound" stuff starting to emerge because of the fact that there
are so many ways today of working with Csound graphically, intuitively,
transparentily, and immediately. In fact, you never need to know or
care that Csound is under the hood! Cecilia was always an excellent
model for this "type" of user, and it is now much improved. You can
certainly expand that sytem by adding modules of your own (but you might
not need to given that it is so extensive already!) Should you want to
make your own graphical front-end for Csound, that is also getting
easier than ever. Given the GUI capabilities in Matt Ingalls MacCsound
and the GUI tools in Cycling74's Max/Msp/Jitter for Macintosh os9 and
osX; and Miller Puckette'ss PD for Windows and Linux that both embed the
entire Csound language as a single external object by Matt Ingalls; and
given the excellent and extensive FLTK support of Gabriel Maldonado's
CsoundAV for Windows, (opcodes now added to Istvan Varga's
DeveloperCsound for Linux).
<p>
Csound is not C. At first glance, it looks like a programming language
with all that text, numbers, and cryptic variable names. But, it
doesn't take a musician very long to realize that the 500+ opcodes are
simply modules that they can patch together with variables. Yes, at the
lowest (and most powerful) level, Csound is text-based, but in less than
an afternoon and some of my original Csound Toots or Chapter 1 from "The
Csound Book," virtually anyone can figure out how to work with Csound
and begin to harness it's power. If you are an intuitive,
"production-oriented" musician that wants to turn knobs, make noises,
mangle the noise you made by turning more knobs, etc. without having a
clue, the Csound is NOT for you. Csound requires that you know
something about software synthesis, digital audio, and signal
processing. If you know something, and know how to use Csound, it is
not too difficult for you to design Csound for Dummies Applications and
Utilities which hide Csound entirely from the tweeker - I mean
power-user.
<p>
Q: Many in the Linux community care quite a bit about software
licensing. It appears that Csound is licensed under research-only
terms that some may find too restrictive. For instance, one can fix a
bug, or add a feature in their own copy, but redistribution with
changes would evidently be prohibited. Is there some reason that the
Csound license is set up this way, instead of having features that
typify open source licenses?
<p>
A: I can tell you this, that it is not Barry Vercoe's intent for
Csound to be restricted in any way. For "education and research"
purposes, one can do whatever they want with Csound. Distribution
seems to be one of the thorny issues. Regarding distribution, John
ffitch, maintainer of the Canonical Csound at Bath University, and
cSounds.com have permission from MIT and Barry Vercoe personally to
distribute Csound. Furthermore, I have permission to distribute
Csound on the CDROMS of "The Csound Book" and "The Csound Instrument
Catalog." How can I help the developers to distribute their versions?
Well, I personally pay for webspace for ALL the key developers so that
they can distribute their versions of the program through cSounds.com.
There really is not anyone creating free versions of Csound that is
not currently able to do what they are doing or what they want to do.
Selling music and samples made with Csound is also OK with Barry
Vercoe and MIT. Of course, selling Csound is not. MIT has sold rights
to develop commercial applications with Csound to Analog Devices and
some other companies and so they have some vested interest in
protecting those contracts and rights.
<p>
Still, we all wish that Csound was totally free, or that the ambiguities
in the licence could be clarified. I am happy to report that Barry and
I have been meeting about this very topic in the past few weeks. I have
been presenting him with the viewpoints of each of the core developers -
what they want to do with Csound, and what wording of the current
license prevents them from taking Csound in this or that direction.
During our last meeting, he contacted MIT's lawyers and we have arranged
to meet with them when Barry returns from Russia and India where he is
doing Media Lab work and Csound work. Hopefully these meetings will
result in a new licence or some new wording that will encourage future
developers in their efforts to improve and extend the language.
<p>
Q: Csound seems like a very nice interdisciplinary tool for students,
bridging across multiple subjects like music, sound, psychoacoustics,
and DSP. What have been some of your best experiences with Csound in
the University setting?
<p>
A: Csound is the ultimate educational platform for students of
Computer Music. In The Csound Book, every bit of synthesis and signal
processing theory are supported and illustrated by complete and fully
working Csound instruments that can be edited and expanded and fully
explored by the student. I have been teaching Csound to undergraduate
Music Synthesis and Music Production and Engineering Majors at the
Berklee College of Music for 18 years. For the past four years, I have
been teaching Csound to graduate students at NYU. I have given Csound
workshops and seminars in Eastern Europe, Western Europe, and
Southeast Asia. I use Csound in my DSP classes both at Berklee and NYU
and in my Max/MSP classes as well. Currently, we are developing a set
of Psychoacoustic tools for Music Therapy students at Berklee and I am
about to introduce a whole new area at cSounds.com developed by my son
Adam (a student of Scotty Vercoe!)
<p>
Csound has always been an excellent tool for teaching and learning
synthesis, acoustics, and signal processing. The Csound Book reveals
virtually all the industry secrets. When my students get Csound into a
major motion pictures or major telivision programs because of the Csound
gigs with Media Ventures or Machinehead; when my students get Csound
into Video Games because of their Csound gigs with Lucas Arts, and
Dreamworks; when my students do Csound work for Rock Stars like Trent
Reznor, Aphex Twin (Richard James), DJ Spooky; when my students get jobs
in Add Agencies, Jingle Houses, and Recording Studios and Csound gets
into national ads with voice talents like Jamie Lee Curtis; when my
students get gigs at Cakewalk, MOTU and other software companies because
they know and work with Csound; when my students publish thier own
Computer Music Books in Korea; when Csound compositions by my students
win national and international competitions; when Csound helps my
students get into graduate schools; when my students find ways a making
Csound work in their musical toolkit, these are some of the most
gratifying things about teaching Csound.
<p>
Hearing that computer music professors and students from all over the
world are using Csound and using The Csound Book is really great,
because Csound is really great - and getting better all the time. It
is gratifying to know that my work has been helpful and inspiring to
them. Max Mathews, the father of computer music is a good friend and
mentor to both Barry Vercoe and I. His MusicV program inspired Barry
to develop Csound and his book "The Technology of Computer Music"
inspired me to write "The Csound Book." Barry's son Scotty was my
student. My oldest son Adam, a Music Therapy major at Berklee, was
Scotty Vercoe's student. Today Adam Boulanger is building tools for
his own Psychoacoustic research in Csound and through his research
tools, introducing Csound to the Music Therapy community. I guess I am
most psyched about the fact that the future of Csound is in the hands
of some great students including Barry Vercoe's and my own very
talented sons.
<p>
In the year I was born, 1956, Max Mathews (the father of computer music)
had a dream and began to realize it in his MusicN languages. He passed
the torch to Barry Vercoe and their light inspired a nineteen year old
composer and electronic musician named Richard Boulanger. I am trying
to pass along what I have learned from them and what I have learned from
my brilliant students and colleagues. I hope it helps, and I hope that
something I have said in this interview inspires some of your readers to
check out Csound Today.
<p>
RESOURCES
<p>
Csound web site
<br>http://csounds.com
<p>
Dave Phillips Article:
<br>http://www.linuxjournal.com/article.php?sid=3187
<p>
"The Csound Book: Perspectives in Software Synthesis, Sound Design,
Signal Processing, and Programming."
<br>Edited by Richard Boulanger
<br>The MIT Press
<br>Cambridge, Massachusetts
<br>London, England
<br>ISBN 0-262-52261-6
<!-- *** BEGIN author bio *** -->
<P>&nbsp;
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<!-- *** BEGIN copyright *** -->
<hr>
<CENTER><SMALL><STRONG>
Copyright &copy; 2003, Michael Baxter.
Copying license <A HREF="../copying.html">http://www.linuxgazette.com/copying.html</A><BR>
Published in Issue 96 of <i>Linux Gazette</i>, November 2003
</STRONG></SMALL></CENTER>
<!-- *** END copyright *** -->
<HR>
</BODY></HTML>
Reference in New Issue View Git Blame Copy Permalink