Fighting with computers

My old analog camera is also giving me trouble. The symptom was that many pictures had just a small fraction of the total field. This can happen when shooting with flash if the sync speed is not correct (flash fires when shutter is half-open only). However this time I was shooting outdoors without a flash. After a few iterations with Google led my to a photo on Wikipedia with exactly the same type of residue I've found on my camera. A few more searches led me this article that explains the causes of the problem and a possible fix. Aging and heat turn a piece of foam inside the camera guts into an oily tar that ruins the shutter operation. Did you think you can keep on using your old camera, maybe not if it as a twenty years old Canon EOS.

One of the bad things about DSLR (aka Digital Reflex) cameras is the tendency to get dust in the image sensor (as these cameras use removable lenses). Whether it is just dust or pollen it may eventually be shown in your photos (like the spot I show on the right: it is just blue sky). For not so big spots, they may go easily undetected. If you want to check for dust in the sensor the simplest way seems to take a photo of the blue sky with the smallest aperture possible on your lens (F22 in my case). Detecting the problem only serves to make you nervous, but fear not, it can be fixed. There are different ideas and people who would talk for or against any of them. I do not feel comfortable risking my camera sensor without reading quite a lot before doing one thing or another. Apparently there are several ideas that can help: Air blower. Dry dust removers. Wet dust removers. Send the camera to the manufacturer for a professional cleaning of the sensor. The first three is something you can ...

Programming when your target system is not based on x86 architecture and you use a PC for development can be done using a cross-compiler. There is a GNU cross-compiler for many different platforms. What if you'd like to test the code without using the target system. There are good news too, as you can use qemu emulator to get a system with a non-x86 architecture emulated on your x86 system. But you might want to get a development system running on your same target hardware. This is interesting if you have a way of accessing the target computer filesystem. It can also be interesting if you want to be able to fine tune the set of versions and libraries to be used by your development system. Here is when buildroot comes in handy. Buildroot allows you to create a development environment for your embedded system around uClibc (which is a scaled-down version of glibc used for many Linux-based embedded systems). With this tool you select the architecture, kernel, compilers and librar...

Some people are keen on the idea of using cellphones as a remote control. After all they are usually around, have a small size, a nice display and even some of them have an illuminated keyboard. Among the choices for interfacing with another equipment, Bluetooth seems to best choice: more standard than infrared and lower power requirements than wifi (besides not many phones have IR or wifi). Around this concept of using your Bluetooth cellphone as a remote was created AnyRemote project. I've tried lately for a home project and I'm very happy with this suite. Yes, it is actually a more complex system than I expected: You cellphone needs a special program to act as a remote, this program in written in Java and you need to download it to your phone. Then server software is installed in your computer and a set of configuration scripts tell your computer what to do when each key is pressed. On the other hand, user menu is provided on cellphone display (there is even a midnight com...

Hardly more than 90 days old, our MacBook 2.4 was already featured here as it has already caused me some trouble. Not a good thing I have to talk about it again: Yesterday it stated to make fan noise when idle, and the display backlight was changing for no apparent reason. After several unsuccessful attempts, I've found this article about resetting SMC as somewhere else I was suggested it might help. Unfortunately though the SMC reset did help with the fan noise it left my system with no ambient light sensor. Whether it was related or not I do not know, but now I cannot use F5/F6 to change the keyboard backlit which remains off. I get a forbidden sign as if the ambient light was very high so as not to require any keyboard backlit. Unfortunately this seems not to be the case in my dark room and it still refuses to allow me to switch the backlit on. The next exercise on the list was to perform a PRAM reset, that did not fix anything either. And, according to Apple support, the next ...

I was not sure what gift I would get for Father's day. A colleague of mine was very happy with his last gadget, a multimedia hard disk that could reproduce High Definition content from its 1TB disk and it could also record from a video input. I already own one (older) version of that (Freecom Media Player) so I was not impressed with the idea, but my friend insisted I should try his unit at home. I brought the system and I hooked it to TV. I tried some HD content I had around and I liked what I saw, so I was sold. I would be replacing my TV computer whose SAT receiver card is no longer in use as I switched to a cable provider years ago. Still that computer was serving me well, still with its original SUSE 8.2. The Iomega unit does have HDMI, components and composite video outputs, plus an optical audio output. It has a host-mode USB socket that accepts external storage (i.e. another hard disk). It can also be connected to a computer by USB (a B-socket in this case) to be used as ex...

A few years ago I was excited when Zinio started (what was to me) a new business: Electronic magazines you can download and see them in your computer display. Zinio model required a DRM-ed software on your computer and Internet access to double-check the binary file you've stored in your computer was one you're entitled to see. Platform-dependent and not so flexible made me walk away from Zinio. However, for a number of years I've been a paying subscriber of Circuit Cellar magazine whose model was, IMHO, simpler and better: a PDF file. Today I've learned that this magazine (that sometimes has featured articles by me) is adding (not moving) a new flavor for their electronic version. One version powered by Mymaganizes.net , that in essence is a Flash-based viewer similar to the one at Issuu . I guess that besides free content the company also manages users subscriptions. By checking on-line I can see that now Zinio has also enabled a browser-based reader that does not r...

A recent project I'm working on needs to behave as a Modbus slave. Not that Modbus is a complex protocol, but it is always handy if you can save yourself the effort of doing your own implementation. After some trouble I've got FreeModbus library up and running. While looking around I've also found some cool tools like modpoll that can allow you query a Modbus slave. And while I had some trouble with the Linux binary (libstdc++5 was missing), the Windows binary runs happily under wine too. Another great set of tools are these ones . You can even connect your Excel spreadsheet to values obtained from a remote slave! It was fun to realize there is even a Modbus for Arduino implementation.

Over the years and hard disk changes and backups and new computers and OS installs I've got a pretty untidy photo collection, scattered across several disks. I wanted to make a clean and tidy library on my main desktop using F-Spot. Unfortunately this program does not have yet a duplicate detection feature (it seems to be available in the latest version though). So I've ended up with many photos repeated on my new library after importing from different backup copies. I thought I could do a simple script to find those files with matching md5sum, no matter the filename, so I could remove the photos that appear more than once. But I was glad to see that somebody did it first . Of course the same idea could be applied to MP3 files or any other type of file. The only drawback, if you want to be picky, is that md5sum covers the whole data of a file, so a change in let's day EXIF data in a JPEG file will render the file as different even though it may contain a duplicate image. Sa...

It's not new. It's not original but it seems to me the easiest way to put together some audio with a synchronized slideshow. I mentioned Slideshare three years ago , but now I've learned they offer a cool on-line service (no software to install on your computer) to create synchronized-audio slides. Vertical printing machine View more presentations from hj43us .

I've never been a fan of Bézier curves , but sometimes they are useful. Maybe my main complaint is acknowledging the fact that I've been incapable of getting a curve just right on the first attempt in any vector editing software. Maybe it is just me. So when I saw that Inkscape was adding support for a new type of curve I have never heard of before I started to pay attention. Of course this is old news for some of you, but I've been busy with other things and I have not checked the development version of Inkscape for quite a while (maybe a sign that I'm quite happy with 0.46 version). The thing is that Mr. Levien was smart enough to develop an alternative to Bezier curves and kind enough to grant a free license of his patented technology to GPL software. Thanks to this Inkscape can brag of supporting a new type of curve not available on commercial software like Illustrator. A library is available on Sourceforge too. But it won't be fair to the effort of Inkscape ...

Barcodes have been growing to pack higher data density. 2D barcodes can pack more data than older 1D codes. Many cellphones can decode barcodes as the are equipped with a camera good enough for the task. There is a cool project that offers code for doing that with a variety of phones, including iPhone and Android. Unfortunately it does not seem to work with my Nokia E71 phone (it has to be some kind of curse, as the built-in barcode software that came with the phone does not work either). However I still can use the phone to take a picture of the codes I'm interested on to have them decoded on-line. You can try this form to decode a file with a picture of a barcode. An alternative to using the cellphone for decoding the barcodes on-line (that can be expensive depending on your data plan) is to download those images to your PC and to use a simple script to get them decoded. I used curl tool for doing that as it has HTTP POST capabilities. It worked great.

Last summer I renewed my two main desktop computers. I was looking for something compact but easily upgradeable. Not very expensive and reliable. I've got good experiences in the past with ASUS barebones, so I went for this one . All but a small detail have worked like a charm since day one. I was amazed to see see that even suspend worked nicely with Ubuntu 8.04. But then I realized the system sound was gone when waking up from suspend. And it seemed the only way to get it back was to reboot the system. Several forums reported the possibility of adding some parameters to the sound driver module so it will reload appropriately when resuming. Unfortunately the two first hours of attempts were unsuccessful and I decided I could live without it. However, days later I've found another post where what it is suggested worked for me too: add these lines to /etc/modprobe.d/alsa-base options snd-hda-intel model=3stack-dig options snd-hda-intel enable_msi=1 options snd-hda-intel single_...

We all love the MacBook at home. For a while we made no use of the built-in Superdrive. However, I noticed that the rubber feet did not work well when I put the laptop on a table: It slided easily while used. I thought it was a poor-design detail, maybe it was not flat enough. A few days after buying the laptop, early this year, I saw the advertising of the new iLife'09. I thought it might be included with my laptop but it was not. A couple of email messages from customer support did not much to enlighten me on how to get my copy for free. A friend of mine showed me I could be eligible for an upgrade for a small shipping fee and so I buy it. Once I've got the iLife DVD is when the problem struck me hard: The MacBook refused consistently accepting the disc. I was not even sure whether another disc might be stuck inside or not. Several tricks to get system to eject the disc failed but I was almost sure the unit was empty. I thought it was a real shame that a brand new laptop was ...

I've just got my upgrade from Apple. Although I bought a MacBook early this year it did come with iLife'08 software. After watching some of the features about the new version I asked Apple for my own copy, that was not free but around $10 of shipping cost. Software install took a long time (more than 30 minutes) and iPhoto browsing more than ten thousand photos needed more than two hours. But after that it was really fun to use the new "Faces" feature. Though not perfect it does an Ok job of detecting people's faces on your photos. On the musical side, the new GarageBand includes a cool feature with music lessons you can download (some are free and some are for a fee). If you have a MIDI/USB dongle you can attach a music keyboard (our cheap eBay dongle worked nicely). iMovie seems to have some advantages too, but iPhoto and GarageBand new features made the switch for us really worth it, even if you have to pay the full price. I've found the new photo slidesho...

As it use to happen, once you search the net for something you realize other people have done it before and hopefully have written about the solution to the same problem too. That has been the case when I was working about a way of suppressing a reasonable behavior of Ubuntu OS on my laptop: When it is wake up from suspend, the user is asked for the password. It is a well thought out security feature but it was annoying for me. I use the laptop mostly while watching TV on my coach (ideal for skipping the ads). However I do not have a backlit keyboard (I envy my wife's MacBook which does). So typing a password with not much light in the room is error prone. Fortunately it was easy once you find the way of changing the system configuration. Here it is .

I've just learned of a very interesting sensor platform . It combines an Arduino, and Xbee wireless module and a Lithium polymer battery charger. Battery maybe recharged by USB. Standard Li-Po batteries are almost 1000mAh. It can also be wirelessly reprogrammed , which is cool. Combined with power management it could achieve very long lifetime on a single charge.

Sometimes you need a calculator to use in the classroom. Maybe you need to solve a 2nd degree equation or you need to know the binary representation of a decimal numbers. I'm sure you can do math, but I've found this online calculator very very useful.

For a new assignment for my students I decided to show them they could build a simple P2P software. So I prepared a simple P2P protocol specification and a sample implementation . The whole system was design with the idea that students might run several peers on a single computer (for testing purposes). Effort was put on making it simple to understand and to implement (and to test), there are many improvements possible that will boost performance but those were rejected in favor a simple system. I did search on the net for a simplistic P2P but I did not find that so I wrote this. I like to hear from other simple P2P protocols you may know.

Like many of you I do have a hard time trying to keep up with all the new services offered by Google. I've been testing a few of them recently and I've found them quite useful: Google Analytics is yet another service that will inform you about who, when and where you're site is getting visits from. Google Sites enables you to create a website just yourself of with a few collaborators of your choice. No HTML knowledge seems needed. Up to 100MB of free storage is provided too. Google Trends allows you to know whether a certain search term is becoming more or less popular lately by know how many searches are using it over time. None of these services is really new but now that I've come to use them I can recommend them. Given they are all free services I cannot complain about the price.