Fighting with computers

| View | Upload your own I'm visiting a school in northern Finland next week. This is the presentation I'm giving. It's intended for first year students so you'll find it very basic, and you'll miss the fun of some demos. By putting it here I have a backup plan if I lose my pendrive :-)

I'm still dealing with a non-responsive eBay seller after I've got burned by a non-working 8GB compact flash. I've seen that many people do not like to talk about this type of failures that happen on eBay from time to time. I'm still trying to get my money back from PayPal so maybe not everything is lost. But now I wanted to buy some cheap control chips for bipolar stepper motors. Nothing fancy with micro stepping or digital current control, just a simple chip that can also be used for other purposes too. I saw this video and I learned about the L293. It is an old chip that several manufacturers mark as deprecated. Instead of going to a local shop I went online to eBay and I saw several sellers have it available. I tend to favor European sellers if the price is right as I do not particularly enjoy periods longer than two months for delivery (something I've experienced first hand from Hong Kong lately). One of the sellers had a price that seemed ok, but they also di...

I know several nice Math software packages, mostly for Windows (Derive, Mathematica, MathCAD, Matlab ...). My university has licenses for some of them but I am not always on campus, using Windows, when I need some help. There are some free math programs too (Scilab, Octave, Maxima, Axiom ...). What it is not always known is that there is an interesting set of on-line calculators and solvers that sometimes can help you get the job done without installing anything. Quite interesting when you are not even using your own computer. For easy calculations and units conversion Google calculator is a neat tool. How do you use it? Just type your calculation on Google search box (i.e. " 5/sin(32) " or " 25 celsius in farenheit " ). Really worthwhile to convert between American and European fuel economy units! But maybe you already have a calculator so this Google feature while nice does more or less the same. You may need to do something more advanced like online matrix calcul...

A few months ago I bought a shiny 20" iMac. While the initial impression was good, I was not happy after the trouble I had installing Leopard and certain incompatibilities it brought. Just when it seemed things were settling down I've got the system just dying on me after opening a large (120MB) PDF file. The screen turned black and then the system rebooted spontaneously. Another computer was on at the same time and it did not experience any problem, so I do not think that was because of a power spike. Today, when I started the system there was a multilingual message in a centered dark square telling me to press the power button for several seconds to shutdown the system (neither the keyboard or the mouse worked). I have never seen that image before (but I failed to take a photo), it contained the message in Japanse too. It happens to be an OS X kernel panic . When I powered on the system again I heard the welcome sound and next two beeps and then three beeps that repeated ov...

While searching the net for possible uses of old hard drive voice coil actuators I've came across this video. A video is worth even more than a thousand words so I'll let it talk.

Many times the answer is on the 'net, so when I wondered if my dead iPod could be fixed I started Googling. This post is one of the answers I have found. To make a long story short: iPods do not like to fall on the floor, they use to stop working as a revenge on the careless user. iPod mini has an Hitachi microdrive (same size as a Compact Flash memory but thicker) inside. You may wonder, as I did, if you can substitute the damaged microdrive with a solid state flash memory. The answer is yes. Have a look. And yes, you can replace the 4GB microdrive with a 8, 16 or even 32GB Compact Flash card to boost your iPod capacity. You can also replace the battery if it is not holding a charge too. Just be aware that not all the CF cards work.

When my son asked for a new MP3 with video player to replace his ancient Creative Zen micro I thought a new 8GB Creative ZEN will be a nice replacement. However the Zen micro units and the Zen V Plus have not been very reliable (at least not mine). It seems the obvious choice would be to go iPod nano . An option I would agree with but because my iPod decided not to allow writing new songs anymore a few weeks ago. Several things seemed to favor the 8GB Creative ZEN: screen size almost double that of Ipod, a built-in radio and a built-in microphone enabling the use of the unit as a voice recorder. On the cons it was the size and thickness factors that played against Creative's. Unfortunately, the 8GB unit was not easy to find, but somehow Santa managed to get one just in time. It was a disappointment to discover the unit display did not to work just after opening the box. However, just to follow the instructions we fully charged the unit and transfered a whole bunch of songs (data t...

While I have to admit I am quite happy with the last Ubuntu version I have to mention several bumps I ran into: To my surprise, the usual way of installing ssh server did not work as expected. After doing sudo apt-get install ssh I've got installed and running the ssh daemon, but no connection was possible. Well, not sure what happened, but now it works ... I cannot trace what exactly the problem was though it seems two daemon processes were launched by error. Realplayer is another problematic application that use to work in previous versions but now it creates trouble . The adobe Flash player is (almost a requirement if you want YouTube videos to play) another tool creating trouble at the moment. The install will fail but some magic can be done to get it working too. VMware's vmplayer is another example of this apparent regression of tools. It was working before but stopped working not. Fortunately help was on its way and it can be fixed too. None of these problems has been...

The second system I installed Gutsy was probably angry with me. Or maybe I was just downplaying Murphy's laws. It was an old Asus Pundit-R computer and it was a mess. The initial install went ok as I kept my /home partition untouched not to loose any data. However since the first moment the screen colors looked awfully washed out. Of course this same computer was just happy with almost any previous version of several flavors of GNU/Linux, so it had to be something new. While Google comes in handy most of the time, the problem is to choose the right keywords. It took me a while (more than I am willing to admit) to find this bug report and the solution . And while doing the silly thing with the Ubuntu logo above, I discovered the GIMP version that comes with Gutsy fails to open a URL. A feature that has been working for ages. ( Fix: sudo apt-get install gimp-libcurl ). In the process of fixing the graphics driver problem something happened to compiz that now prevents me to use any ...

After some weeks waiting to allow the news to settle, I've decided to install the new release of Ubuntu known as Gutsy Gibbon. I have started with my laptop that was most needed of an upgrade as it was still running the same version I installed 18 months ago. At the time, Ubuntu required me to tweak several things to get the laptop running fine and still the memory card reader was a no go. This time installation was faster and everything worked first time (all but the WLAN led, while WLAN worked ok the led showing it was on didn't). No need to fight with any xorg config file to get the right screen resolution. Suspension worked nicely too (but I needed to go to the preferences menu to select the power save operations I wished: closing the lid will suspend the system). For the first time Firefox prompt a Java runtime install that worked ok, giving you the choice of what virtual machine you wanted, too. I've read some claims that battery consumption might be higher on this n...

Given the number of downloads, and the fact I wanted to use the red pen myself, I patched my previous converter code to include that. As before, the perl source code is available for download. The program will convert a g-note proprietary file format into an SVG file that at least Inkscape software (the one I use) is happy with. Luckyly one reader provided this link with the file format specs. Just type dnt2svg.pl your_dnote_file > converted.svg Windows users need to know they can get a free perl interpreter from ActiveState. Those with Apple OS X already have it in place (but you still need to know of to use a terminal).

New rules in France have been set up to punish on-line exchange of files. The new deal between the French administration, the recording industries and the Internet service providers is supposed to protect the artists' revenue. The deal is supposed to be against on-line movie and music exchange but I am not sure how easy may be to detect that a given user is downloading a song whose rights belong to a French corporation or artist. So it may well be easier to rule out any file exchange, just in case. We will see... Not everybody agrees on the idea that preventing music or video sharing over the Internet is going to improve sales figures, though. If the system they are putting in place in France does work, it may well be a market to watch carefully. I won't be surprised if, instead of the expected results (higher revenue for artists), a significant decrease on Internet users happens. Because of this, I think this is a social experiment we need to pay close attention to. Do not fo...

Many vector drawing programs do include a vectorisation tool so a vector representation of a bitmap can be obtained. I have used many times the one that comes with Inkscape program. However, I've just learned of another tool you can use. The fact the tool comes from Stanford makes you hope for very good or superb results. The picture on the left is a bitmap of a vectorised bitmap. The usefulness of that is just as a sample (but, of course, you do not want to get a bitmap of your vectorised output). The picture was taken from a recent Google Talk at our university. What makes this new tool unique is the fact it is an online service. You upload the bitmap from your web browser and after a few selections you download the result in either EPS, SVG or PNG format (the latter is a bitmap format though). The comparison you can find on the tool site shows an impressive performance compared to other vectorisation tools on commercial software (from Adobe and Corel). Update: Since this entry...

I reported some days ago I could no longer use The GIMP on the newest OS X 10.5 , aka Leopard. It transpired the problem was due to changes on X11 support. Apple has moved from Xfree86 to X.org implementation and this move created some trouble for several Xwindow applications. Fortunately the fixes are already available and a new binary I found here is working like a charm on our iMac (this subtle change on iMac's ownership claim has not been yet noticed by my wife). BTW, if you want to try the Time Machine in Leopard you need to now that the external hard disk you use needs an HFS+ partition. So if you just have another one the drive will need to be repartitioned and you will lose all your data. Warning messages are given before though. If you used arhive install, as I did, you'll have around 12 GB with a copy of your old Tiger setup. It may be a good idea to delete it (provided you already had another backup) before using the Time Machine for the first time.

I am sure you've used many times a drop down list to chose from a set of limited choices. One common use is to mark the country when specifying a shipping address. Some websites default to your own country, which is a good thing for the locals but eventually other people will have to select another value from the list. As I am currently based in Spain everything I buy from other countries does not default to my country so I am forced to go down the list. There is a shortcut that works on different operating systems which is pressing the first character of the word you are looking for to go to the first, second, third element, and so on of names starting with that same character. Sometimes this can be much faster than using the mouse. However, I have discovered that the common way of storing this lists does not make my life very easy when searching for my own country. There are several problems: Not all the site use the same list so you never know what is the location of the item yo...

My wife's iMac is dead after the Leopard upgrade (I was about to tell you how fast was the delivery of the DVD from Apple's store). I've seen I'm not alone and I'm going to have to do another type of install that essentially will wipe out all the apps and config already done. This is the feedback I left on Apple's feedback page: I had an almost "virgin" one-month old aluminium iMac 20". I requested the upgrade DVD to go from Tiger to Leopard. Now my system refuses to accept my password anymore. After a blue screen it gets back to asking me my password again (I'm positive I'm typing the right password). Now I have discovered many users are having the same problem. Shame on you Apple. It's really not acceptable. None of the "rm" tricks proposed did fix the problem so I guess I'll have to go through the archive install. This ruined my day. I am not happy. So be warned, do not expect the normal upgrade to work and reserve a ...

Did you ever wanted to play a file on a different device but you were prevented to do so because the file you bought had some nasty DRM inside? Well, I did and I wanted to do something about it. There is a tool that seems to work nicely for this purpose and it does not involves cracking the DRM system. It is tunebite software . It somehow reminds me the idea of Total Recorder but now it does work with videos too. The idea is quite simple: If you can play it you can record on-the-fly from your own computer. I guess it is easier to say than to do it. But this company seems to have done a pretty good job. They claim doing this is not illegal but I cannot provide you legal advice. For me it did the work of enabling my wife watching a DRM-ed video on her Creative Vision:M , which by the way it is a better video "iPod" than Apple's.

There are many open source projects out there. Many of you are familiar with the concept of open source software, where the source code is made available. Not so common is the idea of open-source hardware. What is the idea here? You get the full details of the hardware and firmware as if it were just the code of an open source software project. It is about extending the openness of a project to the hardware and firmware levels. Arduino is one of these open-source hardware projects. It is a family of small printed circuit boards powered by Atmel micro-controllers that can be programed. You develop the code for these micro-controllers using an Integrated Development Environment (IDE) also provided on the project's web-page, available for Windows, Linux or OSX. The IDE is based on Processing IDE I covered a while ago and the programming language is based on Wiring language. The goal is to make user life easier as the development is aimed to artists more than to engineers. The micro...

Digital photography brings yet another way to annoy friends and relatives. Digital photogtraphy is convenient, and you do not have to buy or develop film, so you may end up, like me, taking (and keeping) many shots that are not that great. Thousands of pictures pile up on your hard drive but they are not in a format you can easily share with your grandma (unless she is Internet proficient). Two online services I have found quite useful are flickr and Google's Picasa. They make easy for you to share your photos even when you are on the go. However, if you want to create something oriented for people who at most are capable of playing a DVD then you need other tools. Some DVD burning programs can help you creating a simple slideshow of your photos. However my experience is that just a sequence of pictures without a soundtrack is not something people are going to enjoy. Another problem is that even if you have sound, the pictures without any motion look boring and uninteresting most o...

Contrary to what the name may suggest this device is not a mouse but a trackball. At around $100 it is an expensive alternative to traditional mice. Kensington trackballs have been around for more than 15 years and I have read good things about them. I decided to judge by myself and I bought one unit. The bottom line is that except the annoying noise and feel of the scroll ring the device is quite nice. The optical tracking is hopefully more precise and less sensitive to dirt than older mechanical systems. I have contacted Kensington customer support to report the problem, but given what I have read on the net it seems to be a common complaint from users. I have not yet heard from Kensington but I have thought you may want to "hear" and feel it by yourself before buying one unit.