Check out gist!

“Boundary Functions“

is a an interactive media installation by artist Scott Snibbe. I like it very much, have a look:

“Boundary Functions“

is Ted Kaczynski‘s doctor thesis [abstract] from 1967. It was too difficult for the readers like Maxwell Reade from Kaczynskis’s dissertation committee:

I would guess that maybe 10 or 12 people in the country understood or appreciated it.  - Maxwell Reade [src]

Forensic sketch of the Unabomber by Jeanne Boylan

Because all configuration files by others didn’t work for my setup, here is what I did to make it work. This tutorial assumes, you are using Ubuntu 10.10 Maverick Meerkat and lirc 0.8.7.

1. Install Lirc:

sudo apt-get install lirc

At the end of the installation, there’s a menu, where you have to choose your remote. Select “ATI/NVIDIA X10 RF (userspace)” and “None” in the second dialogue. If you made a mistake here, just fire up the config dialogue again by typing

sudo dpkg-reconfigure lirc

2. Edit the configuration files

Now you goto to the directory, where the main LIRC configuration files are located.

cd /etc/lirc

Here you have to edit the file hardware.conf according to my file, that you can find on gist: https://gist.github.com/859369#file_hardware.conf.

Note that you don’t have to load kernel modules like lirc_dev and lirc_atiusb like lots of old tutorials suggested, if you use this hardware.conf.

Before doing anything else, you should stop the lirc daemon with

sudo /etc/init.d/lirc stop

Next you have to edit the file lircd.conf, located in the same folder. If you really have exactly the same remote, you might try to use my lircd.conf first: https://gist.github.com/859369#file_lircd.conf.

If this doens’t work perfectly (you can test your configuration with the steps described below), you should try to create this file with the handy utility tool irrecord. Start it with

irrecord -n -H atilibusb ~/lircd.conf

and follow the onscreen instructions to give a name to each key on your remote. If everything worked out, just backup the old lircd.conf and copy your newly recorded one there:

sudo mv /etc/lirc/lircd.conf /etc/lirc/lircd.conf.bak
sudo cp ~/lircd.conf /etc/lirc/lircd.conf

3. Test the connection

At first we have to restart lirc:

sudo /etc/init.d/lirc start

Now we make use of the handy tool irw, that comes bundled with LIRC and shows, what you are receiving. Start it by typing:

irw

If you hit buttons on your remote now, your terminal window should react to every button and look a lot like this.

4. Configure <program-name> to be controlled by your remote

If everything worked out until now, you are finished with configuring lirc. Now you should look out for a tutorial on how to make it work with the programm, you want to control. There are tutorials out there to remote control media centers like XMBC or MythTV, media players like Amarok, Rhythmbox and Exaile and nearly every other programm, where a remote control makes sense. With irexec, which also comes bundled with lirc, you can execute everything you can type on a terminal window with the press of one button.

I’m currently still experimenting, but I’m going to control at least Exaile and Totem on my box and I also want to shut it down with my remote. In the next days, I will post an update here, that shows how to do it. Stay tuned.

P. 114, Listing 1.6.1, Line 5

Original:

double* ptr = buffer + 1024; /* point to last element */
double maxval = 0.0;
unsigned long pos = 0;

while(--ptr != buffer){
    if(*ptr >= maxval){
        maxval = *ptr;
        pos = ptr - buffer;
    }
}
printf("the maximum sample is %f, at position %d\n", maxval, pos);

Problem:

The first thing to notice here is, that ptr initially doesn’t point to the last element (as stated in the comment in line 1), but exactly behind the end of it. But it’s just a comment, so don’t mind.

The real problem is line 5, where we have a while loop which is decreasing as long as –ptr != buffer. But buffer points exactly to the first element of a buffer of float values, so in the original function definition, the first value will never be used. The solution is just to replace the comparison in line 5 with –ptr >= buffer, so that the loop stops, when all elements of the buffer have been checked.

Corrected:

double* ptr = buffer + 1024; /* point behind last element */
double maxval = 0.0;
unsigned long pos = 0;

while(--ptr >= buffer){
    if(*ptr >= maxval){
        maxval = *ptr;
        pos = ptr - buffer;
    }
}
printf("the maximum sample is %f, at position %d\n", maxval, pos);

P.268ff., siggen.c

Problem:

There’s a strange error, when you go step by step through the tutorial to create siggen.c, a plain test programm to test a small lib for creating oscillator-functions. You are told to use the portsf library, that comes with the book, to create an outfile in 16bit format. What you are not told is, that this library has an option to dither audio data before saving, which is not used by default. This results in digital clipping of the audio files you create, some amplitude values, rather then hitting 1.0 are reversed to -1.0.

On the picture, you can see, how the result looks, when you try to render a sine wave with an amplitude of 1.0. When you listen to such a file, you will recognize the clipping as a distorted, crackling noise. But as already pointed out, you can avoid the whole problem by utilizing the already included dithering option of portsf.

Solution:

Use the following chunk of code just after creating the outfile with portsf. It will activate the dithering. If you want to have a look, have it is done in the library, look for the string “PSF_DITHER_TPDF” in the function “psf_sndWriteFloatFrames” in portsf.c.
It is assumed that ofd is the ID of the soundfile in portsf.

if(psf_sndSetDither(ofd, PSF_DITHER_TPDF) != 0){
        printf("Error: unable to activate dithering.\n");
        error++;
        goto exit;
}

It’s perfect!

you can download the sources from the download-page of the lm-sensors-project or just by typing this in a terminal window:

wget http://dl.lm-sensors.org/lm-sensors/releases/lm_sensors-3.1.2.tar.bz2

now you should unpack the archive with the sources by typing and change to the extracted directory:

tar xjf lm_sensors-3.1.2.tar.bz2<br />
cd lm_sensors-3.1.2

before you proceed, you should resolve all dependencies for the build-process by typing:

sudo apt-get install build-essential gcc flex bison librrd-dev rrdtool perl checkinstall

installing it is then relatively easy, just type:

sudo checkinstall -D

answer the first questions by just pressing enter until it your terminal looks like this:

 Das Paket wird entsprechend dieser Vorgaben erstellt:

0 -  Maintainer: [ boundaryfunctions ]
1 -  Summary: [ Package created with checkinstall 1.6.1 ]
2 -  Name:    [ lm-sensors ]
3 -  Version: [ 3.1.2 ]
4 -  Release: [ 1 ]
5 -  License: [ GPL ]
6 -  Group:   [ checkinstall ]
7 -  Architecture: [ i386 ]
8 -  Source location: [ lm_sensors-3.1.2 ]
9 -  Alternate source location: [  ]
10 - Requires: [  ]
11 - Provides: [ lm-sensors ]

Geben Sie die betreffende Nummer ein, um die Vorgaben zu ändern:

here you should type “3” and input “1:3.1.2-fromsources“. this way, the automatic updates will recognise your installation of lm-sensors as a newer version than in the ubuntu sources – and stop bothering you to “update” to that older version. however, if there will be a newer version of lm-tools in any of your packetsources, update will install it.

then you should type in “10” and answer the prompt with “perl,rrdtool“, so your packagemanagement knows,  that lm-sensors depends on perl and rrdtool to work properly.
your screen should by now look like this:

0 -  Maintainer: [ boundaryfunctions ]
1 -  Summary: [ Package created with checkinstall 1.6.1 ]
2 -  Name:    [ lm-sensors ]
3 -  Version: [ 1:3.1.2-fromsources ]
4 -  Release: [ 1 ]
5 -  License: [ GPL ]
6 -  Group:   [ checkinstall ]
7 -  Architecture: [ i386 ]
8 -  Source location: [ lm_sensors-3.1.2 ]
9 -  Alternate source location: [  ]
10 - Requires: [ perl,rrdtool ]
11 - Provides: [ lm-sensors ]

now press enter a last time and after loads of terminal-output, lm-sensors should be installed. let it detect your sensors with:

sudo sensors-detect

you  should just enter yes to all the questions it asks, especially when it’s about adding modules to your /etc/modules. if it did then one last step would be reloading the kernel-modules:

sudo /etc/init.d/module-init-tools restart

you are finally done! enter “sensors” in a terminal to let the values of your pcs inner life come to the desktop. it might be handy to use some frontend to lm-sensors like ksensors, xsensors or computertemp.