Category Archives: Technology

Early impressions of my RaspberryPi

RaspberryPi sitting in its case without the upper half
Last year I ordered a RaspberryPi; I wanted to check out the hype and, who knew, maybe I’d get a decent media (or at least music) player out of it. The machine arrived right in time for Christmas, together with an SD card preinstalled with Raspbian and a USB power supply.

Wow, the CPU of this thing is slow. I was lucky to get the new version with 512MB RAM, I guess. Any CPU-heavy task feels extremely sluggish, be it aptitude, X or — beware! — watching videos. The GUI software package that comes with Raspbian is all but useless, too, so I soon decided to stick to a native terminal.

I was quite disappointed with the video performance which resembled a slide show; I had wanted to use the Pi as media center, after all. So I did some research and learned that there is apparently only one player which can harness the hardware video decoding capabilities the Pi has to offer: the OMXPlayer.

Turns out Raspbian with OMXPlayer does a better job of playing full HD videos than my gaming PC, and without the noise and barely any heat. Of course, you should not start X but run the player from shell (yes, that works!); not the most intuitive interface — and you have to change the terminal font if you use a big TV — but very efficient. Files are stored on an external HD connected to another PC which the Pi mounts via ssh. So far, I have not experienced any problems with this setup.

The only sore point has been the board layout; the connectors you can’t go without (Ethernet, USB, HDMI, AC) face three different directions, so the Pi is awkward to place if you want to run all cables to the back. Some minor annoyances are missing codecs, for example WMV, and a handful of inconveniences in OMXPlayer.

I have not yet tried using XMBC which is supposed to work well. Installing it on Raspbian does not seem to be straightforward; maybe I’ll try out Raspbmc on another card. Does anybody have experience with that?

How to fill your ereader

Reading free Sherlock Holmes EPUB

Back in January when I bought my ereader, I had doubts whether I would be able to find enough quality content to read on it, given that I don’t buy DRM which still dominates the market. By now I have found enough sources; in fact, I am not quite able to read it all. Here is what I have been reading, in arbitrary order.


For free

  • Baen Ebooks has a free library.
  • Smashwords has many free titles; it is common for authors to give away extended prologues or even first volumes of series.
  • The Firefox plugin GrabMyBooks allows you to pack any web content as EPUB ebook. I regularly do so with CACM and Flash Fiction Online.
  • There are some books floating around the open source community. For example, I discovered Pro Git recently.


  • Project Gutenberg offers English classics that have entered the public domain in multiple formats.
  • Gutenberg DE is the German version. Sadly, there are no downloads, but you can grab the text.
  • Project Runeberg is the Swedish version of Project Gutenberg. They have download as plain text and HTML which is easy to convert.

Over these last year or so, EPUB has been entering more and more publishing heads. I am particularly excited about Tor’s move to drop DRM; huge amounts of science fiction and fantasy are viable in electronic form now. Tor has a nerdy audience (both readers and authors) so maybe they felt more pressure than other publishers; let’s just hope that their example catches on.

Once tools for creating EPUB books become better, it will be increasingly simple to offer ebook versions of your content, be it fiction book, scientific article or tech tutorial. In my opinion, the phase of early adopters is past: with the spread of EPUB, ebooks have left the confines of big publishing houses behind and become a medium of the crowd.

Pretty Math on Wikipedia

In the days of MathJax, the math images on Wikipedia look inferior by a huge margin. The MathJax guys got us covered; they provide a userscript1 that dynamically injects MathJax into Wikipedia sites2. It may load a little longer, but I think this is worth the wait:

Wikipedia Math Vanilla

Without MathJax

Wikipedia Math Mathjax

With MathJax

  1. Userscripts are pieces of Javascript your browser executes on top of any website. Firefox users use Greasemonkey, others see here.
  2. Make sure to change the @include to http://** so the script works on all Wikipedias.

Quick Images with TikZ

How do you create high-quality technical images for documents, your website or posts on Stack Exchange? I have used tools in an ad-hoc manner for a while and have become frustrated lately. Once you have used TikZ1 with \(\LaTeX\) most other tools feel inferior. The only problem is: TikZ is a \(\LaTeX\) package and can not be used on its own. So how to convert TikZ to say PNG comfortably?

\(\TeX\)-guru Martin Scharrer comes to the rescue: he wrote the package standalone for exactly this use case. Based on his explanation on tex.SE I built a small bash script that does all the repetitive work for you. With one simple command, this

%p% \usetikzlibrary{arrows,automata,positioning}
\begin{tikzpicture}[shorten >=1pt,node distance=2cm,auto]
  \node[state,initial]    (q_0)                {$q_0$};
  \node[state,accepting]  (q_1) [right of=q_0] {$q_1$};

  \path[->] (q_0) edge [bend left]  node {$a$} (q_1)
            (q_1) edge [bend left]  node {$b$} (q_0);

becomes this in a matter of seconds:


Get tikz2png on GitHub and enjoy!

  1. Check out the awesome gallery of examples and the comprehensive manual.

New Plugin: Cite & List

Simple Bibliography

A simple bibliography with some citations

Finally! I have needed—and wanted to build—this WordPress plugin for a long time, and now it is done. Because I am so bad at making up names, I called it Cite & List because that is what you can do with it: cite articles and list your publications. Both tasks are easily done with shortcodes; users of \(\LaTeX\) will feel right at home. You can also have everything look exactly the way you want it to, thanks to the use of bib2tpl.

Head over to the plugin repository and have a try! I like how the plugin turned out; hopefully I will have ample opportunity of using it, that is get to writing more sciencey posts.