Fighting with computers

Testing PCL 2.0 Kinfu_app

2012-01-21T00:06:00.002+01:00

I borrowed another graphics card from a friend and this time it was the right one: Nvidia GTX 560 Ti with 1GB of RAM so I was able to test drive the new open implementation of the Kinect Fusion. First result is really promising. A couple of times I've got out of memory errors when starting the application but it was unclear to me whether it was main system RAM or the graphics' card internal memory.

Pressing 3 you get the current point cloud written to disk. I am really shocked by the accuracy of the real-time results. I am getting around 20 fps. Definitely worth trying, but remember you'll need a powerful power supply too. I borrowed a 1.000 watts PC supply, sweet.

Testing Kingfu (or not)

2012-01-19T19:07:00.001+01:00

Once I realized all the work done for compiling PCL 2.0 was useless with my current graphics card I mentioned to a colleague the problem who was kind enough to lend me a Nvidia FX 5800 CUDA-enabled graphics card with 4 GB of RAM. I thought it was beyond the requirements of Kinfu so I did not bother checking it out before doing the installation.

First problem was that this card hardly fit inside my computer. Later I found out my power supply just lacked the proper connectors to power that graphics card. I asked for help and I have got a 1000W PC power supply. This one has all the connectors needed but I am not fitting it inside my computer box.

Once I was convinced of the right way of connecting the 8 pin PCI-express additional power socket, which was all but obvious to me, I fired up the system and it came up nicely. But, once again, I was defeated by the hardware: It turns out this board is not a good match for running Kinfu either. Though it has 250 cores, it lacks the computing skills needed for the job.

It was then when I realized I should have read first: This message talks about hardware requirements and this other page mentions the capabilities of different Nvidia card. Hopefully tomorrow a friend will lend me his GTX 470 that is 2.0 compliant and it should be good to go.

Kinect Fusion open sourced!!

2012-01-14T00:56:00.001+01:00

I was impressed when I saw the results presented in SIGGRAPH'11 about Kinect Fusion by a group of people from Microsoft Research. They manage to get a fantastic real-time scene scene registering using a software they named Kinect Fusion. A couple of papers were published explaining the system architecture and some videos shown the great performance they were obtaining.

Today I have learned that an open source version is being built around the Point Cloud Library and the sample video looks equally promising. But development is only going to be supported on the upcoming 2.0 version of the library.

I am going go give it a try as soon as I manage to compile the whole thing.

Ouch: After fighting with CUDA install (driver, tools, sdk) plus VTK library that was not installed plus some more fiddling with cmake and ccmake I manged to compile the current version of PCL2.0 but to no avail, as kingfu_app is not happy with my oldish video card (GF8400GS) and I get this lovely message instead of any relevant output "Kinfu is not supported for pre-Fermi GPU architectures, and not built for them by default. Exiting..."

Software for 3D scanning using Kinect

2012-01-12T10:51:00.002+01:00

Nicolas Burrus' company has been kind enough to make available software for 3D scanning using a Kinect device that anyone can use for both Windows and OSX.

What you obtain is a colored point cloud and not a mesh, but using software like meshlab you can turn that into triangular mesh.

The way you use this software is by handholding your Kinect and moving it around the object or room you want to scan as if you were painting all the space. The point cloud is growing larger every time you move to a different area of the scene or object.

Result is not as impressive as Kinect Fusion demos but, contrary to the former, this one is available. I guess the will keep on improving the system to obtain better spatial resolution with less noise.

Direct drive extruder

2011-12-29T16:48:00.003+01:00

Once I have got my Prusa Mendel 3D printer working, I have started to look around for improvements. The thing I was less happy with was the clunky extruder, made of a geared drive with printed gears. People in the forums mention it has a limited life of maybe one hundred hours before one or more teeth give in.

I thought a direct drive was an obvious choice only if extruder stepper might have enough torque. Then I learned that Orca v0.3 is using a direct drive using a brass insert. I looked for available designs on the Thingiverse for NEMA 17 motors and I have found this one. With some changes I have make it work.

But not before I replaced one StepStick by a Pololu stepper driver on my RAMPS board. The reason is that to achieve the required torque, the motor needs to be driven slightly above the 1A limit of StepSticks. The other required change is to add some cooler to the A4988 chip so it can properly dissipate the additional heat.

I guess 3mm filament is quite more challenging to make it work with a direct driver extruder than 1.75mm one.

Update: I designed a replacement for the extruder above that uses much less plastic that hopefully will perform better too. The replacement was printed using the yellow extruder part you can see being printed in the video above.

Arts exhibit

2011-11-20T19:17:00.001+01:00

I've been quite busy lately so I've not been posting news but doing new stuff. A few weeks ago a new exhibit it the City Museum of Valencia by local artist Rubén Tortosa stated and one of the pieces was this one, which I designed and programmed.

It is an interactive installation that grabs the visitor silhouette and then it draws it onto the wall at a random location. Drawing accuracy is not intended (or so I was told by the artist). We went for a very simple design, based on my vertical plotter, and a Kinect device was used to gather the images. You can see below a sample of some the drawings of the very first days of the exhibit.

The exhibit will be open till the end of this year and there is no entrance fee. Together with the installation there is a set of interesting pictures I have nothing to do with.

Update: Wow, we're on the Arduino blog now. Arduino code is quite unremarkable as we use a couple of Pololu motor controllers driving the stepper motors. Processing code is a bit more interesting (or so I think).

The beauty of OpenSCAD

2011-11-02T10:48:00.002+01:00

All the CAD software I have used in the past was based on a GUI. AutoCAD does include a language so you can type commands and create macros too. But the way OpenSCAD is surprising (to me) and very useful: You "program" the objects you want to create. It is all based on a scripting language and the concept of constructive solid geometry. You can define basic shapes, like cylinders, spheres or cubes and then operate them to obtain the design you need.

You can experiment with this technology in Java3D too.

Once you have created your design, you can save the result as a variety of file formats, including STL. STL format is supported by most 3D printing tools, including Reprap project software tools (and Skeinforge). Many of the objects available in Thingiverse.com have been created this way.

Calibrating RepRap Prusa

2011-10-23T18:12:00.002+02:00

I thought my troubles were over once I've got all the parts for building my 3D printer, including the replacement for some defective parts.

As usual, I was wrong: Once I have finished building it and tested all the electronics it comes the moment to select a working firmware. There are several choices for RAMPS hardware but I selected Sprinter firmware as it includes acceleration control plus many people use it. But firmware alone is not complete till you've added all the different adjustment parameters so your hardware works together with the firmware the expected way (ie. a 10 mm move in the G-CODE causes a 10 mm move in your printer).

I was excited because once I tested with a thermometer that the hot-end heating and temperature reading was working nicely I thought it will be easy. I used RepSnapper for this basic tests, and next I tried to print a text object. Result was ok, but measurements were still a bit off. But when I attempted the design in the center of this picture the result were less than acceptable.

As many people suggested to use Skeinforge, and the recommended front-end was Pronterface I downloaded the whole thing and tried to go through a calibration process. I've found very useful the steps detailed here. Unfortunately my attempt at calibrating my printer faced two different problems. On one hand the default configuration I'm using for skeinforge 41 is feeding way too much PLA into the extruder (a big reduction in the feed speed in the Speed tab of SF41 seems to be helping). But the second problem is that I am having random lock-ups while printing. This problem appeared only now that I've moved the printer to my office, where I'm using a Linux PC. I can see that USB gets disconnected (only if RAMPS is powered) while printing. I guess it is an electrical problem, so I'll try both a new power supply and a better, shielded, higher-quality and shorter USB cable.

I am not very impressed by the end result of using LM8UU bearings. My x-axis is smooth only half way (I guess because the rods are not perfectly parallel) so I need to bump up the driver current for it not to lose steps (which gets the motor quite hot after a few minutes). Y-axis is smooth but less than I was expecting too. Z-axis is ok but still the motors need a good amount of current not to lose steps.

I've enjoyed the ride quite a lot, but I was expecting a better result. Still, I guess that as soon as I manage to get decent calibration I will start being happier with my Prusa that I am now.

By the way, I think what it is missing in the design is a LED light to lit the part being printed.

Finishing my Reprap Prusa 3D printer

2011-10-13T12:48:00.000+02:00

It's been a long wait to finish building my Reprap Prusa Mendel, to source all of the different parts and then to wait for some replacements of defective electronics. The building time has not been very long as I have had long waits in between, but I'd say it can be easily done over a weekend if you have all the parts.

Now I have to configure it and to master into the use of the system. My total cost is near 500€ and I have chosen some hardware to be better than average, so I guess cost can be driven down a couple hundred euros if you really push it to the bare minimums. I do not have yet any printed samples to show you though.

I can mention the companies I bought from that have given me a good service: XYZ printers (hardware), reprap-fab.org (plastic & extruder), RepRapWorld.com (electronics & PLA filament), Zapp Automation Ltd (stepper motors).

One of the things that have worked for me that can allow you to save so cash is to use both, the stepper motors and the belts, from two old EPSON printers for X and Y axis. They have enough torque to move the two axis well enough. Z axis, however, needs a more powerful motor. As I am using LM8UU bearings for my axis, I am not sure the same is true when using PLA printer bearings.

Anyway, I can recommend this project as a very entertaining one, but unless you are buying a full kit, I am afraid the process of sourcing all the parts may be time consuming. I know that MakerGear is selling a full kit in USA, but I was afraid it might become very expensive for people in Europe once you throw in shipping, taxes and customs.

All along the way, Reprap forums proved an invaluable source of information.

A bit more RSA

2011-09-28T18:36:00.001+02:00

I really don't like when I do not understand anyone's code, so it takes me a bit of effort till I do my own homework to create my own version of things I can understand. Being a teacher, I always find troubling not to be able to explain things to my students, so I used some time to create my very own RSA implementation. I've found a very good reference text here.

My perl program takes three parameters data, encryption (or decryption) exponent and module and it returns the encrypted (or decrypted) version. As it uses BigInt library it should be happy dealing with any of your big numbers. You can find a Java implementation in the above mentioned text too.

#!/usr/bin/perl 
use Math::BigInt;
if($#ARGV<2) 
     {print "Usage: exp, module\n"; exit 2;}
$a = Math::BigInt->new($ARGV[0]);
$b = Math::BigInt->new($ARGV[1]);
$c = Math::BigInt->new($ARGV[2]);
print "out=".($dec = $a->bmodpow($b,$c))."\n";

Contrary to what may look, bmodpow has been implemented to be computationally efficient using repeated squaring technique.
Example:
I have created an RSA keypair before choosing public exponent to be 3. The numbers seem to come out of thin air but I created them with a software tool mentioned in the previous RSA post. The plaintext 1234567890 (as a number and not as string) was selected as it was easy to type.
$ perl myRSA.pl 1234567890 3 0x102421060aad49ec2521203b28
ffdccc73b2b55b7e4f6e73b5ad31dcc240cdc8883fd220fff0a218d16
ec6cbd8a713aa907bd9ac46fd4f622b639de83aa5f4f752f6953960a
363e7c18d3bbdb7b93ff5c9ee07a2de7ba1fe46545da35d1cb92f926
c691e7415b253ad9047547285bc79e0ad915ac2b2b83722ad3d8fc
001aab7
cyphertext = 1881676371789154860897069000

$ perl myRSA.pl 1881676371789154860897069000 0xac2c0aeb1
c8dbf2c36b6ad21b553ddda27723925434f44d23c8cbe8818089305
ad536c0aaa06c108b9f2f32906f6271b5a7e672d9fe34ec1ced13f02
7194df9e19960c0e9b793efd65c4a68f9cabfa1dbe904d5ade76bf2d
83091c17d687b6d04323abd935676379e5ada2cf6892846586360d9
80c9a2cec1bd7cff55566a6b 0x102421060aad49ec2521203b28ffdc
cc73b2b55b7e4f6e73b5ad31dcc240cdc8883fd220fff0a218d16ec6c
bd8a713aa907bd9ac46fd4f622b639de83aa5f4f752f6953960a363e7
c18d3bbdb7b93ff5c9ee07a2de7ba1fe46545da35d1cb92f926c691e
7415b253ad9047547285bc79e0ad915ac2b2b83722ad3d8fc001aab7
cyphertext = 1234567890

Update: I've found that Crypt::OpenSSL::Bignum is more than a thousand times faster doing the modular exponentiation of RSA. So avoid the BigInt approach if speed matters to you.

Playing with RSA

2011-09-14T12:23:00.001+02:00

A recent assignment required me to dust off my knowledge of RSA (public-key encryption algorithm). While it is something I do teach every year, I usually do not have to fiddle with the code. So when I was needing a pair of keys (public+private) for some test I needed to look around for some key-generation code.

Once I've got my pair of keys I was surprised with this implementation of RSA encryption in perl:

<br />#!/bin/perl -sp0777i<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<j]dsj<br />$/=unpack('H*',$_);$_=`echo 16dio\U$k"SK$/SM$n\EsN0p[lN*1<br />lK[d2%Sa2/d0$^Ixp"|dc`;s/\W//g;$_=pack('H*',/((..)*)$/)<br />

However, the fastest way to get you working is using OpenSSL's genrsa command.

Remote Desktop is gone

2011-09-06T12:51:00.003+02:00

Last year I bought a small notebook to keep me updated of what was available in Windows 7. Being a small computer, using it for a long session and, in particular the mouse pad, is not very pleasant. So while I am not on the go, I rather would prefer to access this computer remotely to use my desktop's bigger screen and more comfortable mouse.

I was shocked when I learned that Microsoft had "streamlined" some versions of Windows 7 so some features were missing for some of them. I later learned that Windows 7 Home Premium does not include the Remote Desktop server that was common in Windows XP.

I occasionally use remote control tools like TeamViewer with great success (or other variants of VNC) but the main problem is they do not work as smoothly as Remote Desktop Protocol (RDP) nor they allow you to resize the desktop area at log-on time.

One colleague of mine mentioned, while I was complaining about the missing Remote Desktop on my notebook, that there was a hack to get back Remote Desktop. I tried it, and it worked like a charm. Not only you can get Remote Desktop service back, but it is possible to get RDP concurrent sessions too.

Feeling the RepRap itch

2011-08-24T22:54:00.003+02:00

Not that the RepRap project is something new, but for a set of reasons I am now getting quite interested on it. Still, since my last post, there is a lot of information to process, but this time I am more willing to use some time reading the forums.

There are also some companies that are selling complete kits of 3D printers inspired by RepRap guts (but that claim no percentage or self-replication feature).

The basic idea is to have an XY-table where a plastic extruder can deposit layer after layer on what becomes the Z-axis. Current versions of the control electronics receive and interpret commands in g-code format from one of several possible control programs (Skeinforge, RepRap, SuperSkein, ReplicatorG, ...).

Now I need to learn a bit about 3D design software, though I have discovered a few interesting programs, like MeshLab, Wings3D or OpenSCAD. The latter being a script-oriented design approach, very interesting and useful.

For the moment I am still considering what printer or kit to buy. There is plenty of choices to make in this small world.

Your phone is your 3D scanner

2011-07-21T13:11:00.008+02:00

Or it can be, with the amazing ProtoFly project. In short it allows you to take a few pictures of an object and using their Windows-only software pictures are uploaded to Autodesk servers and a 3D model of your scene is obtained.

Either small objects, the interior of a room or the outside of a building can be "scanned" just with a cellphone camera. And don't underestimate the power of this technique (photogrammetry). I have been more than impressed with the quality of the output mesh. And given that the service is free of charge I cannot complain about the price :-)

Once you've got the 3D model of your scene the next problem is how can you start editing it and showing it to others. I have found a very nice piece of software called MeshLab that does a great job and it is a multi-platform open-source solution.

But the coolest thing is that there are some cellphone apps that can show a 3D object too. I am still fighting with one of them called "Shader Devel and 3D Viewer" that might do the job once I figure it out.

The video below shows the first capture I have attempted using just 2 Megapixel images. Please note it is not a video but a 1080 rendering of the textured 3D-model (scene has not been properly cleaned up so some objects are levitating into the air).

Location recording Big-brother style

2011-07-18T12:04:00.003+02:00

A few weeks ago there was a lot of noise on the news about how different providers were handling the location information obtained from smartphone users. I had a look at what was available (user level) on the Android platform. Latitude is a software from Google that allows you several types of location information storage and processing that can be fun, scary or terrifying depending on how you think about it.

Most of the recording is disabled by default (at least this is what we are told) so you do not have to worry. Whether some recording is done on the provider's side or not I do not know. We all know, however, that cellphone carriers do collect location information of all their customer's cellphones.

What Latitude offers you is the possibility of using your smartphone location capabilities (GPS+GSM+wifi based) to provide updates to your Google account so you can:

Check your (cellphone) location anytime on Google Maps.
Check the location of other users that willingly share it with you. You can track your kids, employees, work mates, etc.
Get a report of your total traveled miles in the last month, week, etc. With details of all the different locations you've been to.
Get a detailed usage of your time: hours at home, at work, on the road, etc.
Get recorded data in KML format (XML based).

There is an API to enable the creation of applications that use this information for new purposes too.

I can think in multiple useful uses of this service and of some not so nice ones too.

Next time you're telling your husband you are at a meeting in the office, think it twice :-)

So what is this Google+ thing?

2011-07-09T12:26:00.002+02:00

I've got an invite from a former student to join Google+ social network. Yes, I'd say it is a social network which, as Buzz was an attempt to mimic Twitter, tries to mimic Facebook (others may use a more agressive term).

I like the idea of having a way to create more categories than just the "friend" relationship of Facebook and the fact that this categories (they call circles) are not closed but you are free to open as many as you want. I like the idea of this circles to be able to intersect. For example you may have a coworker that happens to be a friend too, so you can have her in both circles (work + friends).

Android Google+ application includes a cool feature of automatically uploading pictures taken with your cellphone (and videos). Ok, maybe the latter may deplete your battery quickly, but you have the choice of limiting when uploads may or may not happen.

The number of invites you have initially is not high, but as soon as you start adding people to your circles you get more invites so I'd say the growth of the network is not very limited at the moment.

As a user that started trying out Buzz and later giving up I am not certain at the moment on what the future will bring to this new service. On the graphical design & GUI side I'd say that Google+ seems to require much more screen real state that Facebook.

Google+ has the big advantage of good integration with some other Google services like Picasa and Gmail (and I guess some other I have yet to discover).

Apple knows how to make friends too.

2011-06-24T10:31:00.008+02:00

Sony has presented itself during the last years as a company that has no problem suing their own clients and fans. Several lawsuits against hackers that unlocked previously existing features on some Sony products were dragged to court. I do not think this is a smart move.

Corporations need to understand that customers are a blessing and not a curse. Even if they do not plan on using the product they are buying the way the corporation wants them too. I do not think a company would be offended if I am buying a TV set just to use it as a door step. But even if the are, they can keep that feeling to themselves as they are keeping my money too. Business is more about making money and less about exerting power over your user base.

Apple has been involved in several lawsuits recently to prevent other corporations (i.e: Amazon, Microsoft) to use the term "App Store". It is unclear whether the term is too generic to be protected or not, but it does not look good for Apple at the moment.

But what really pisses me off is that now Apple is bullying the start-up of a friend of mine, Amahi, not to use the term App Store too. On one hand I guess my friend should be proud for his company to be put in the same basket as Microsoft or Amazon but I am pretty sure his company's revenue is just peanuts compared to the others. But on the other hand I think it is the wrong PR movement. You do not get popular by suing kids or small firms. And while a C&D is not a lawsuit, it is the last warning before the elephant jumps on top of your company. I think it is better to compete in terms of how good your technology is.

Splines for smoothing a shape

2011-06-14T22:15:00.013+02:00

Some code for smoothing out a shape, as a curved appearence works better than the shape made of straight lines. 2D splines code was found in processing.org forums. Base points of the shape are marked by red dots. Kinect was used to extract the outlines.

type="application/x-java-applet"
archive="splines.jar"

standby="Loading Processing software..." >

Source code: splines
Built with Processing

Use Processing and Kinect in Ubuntu

2011-05-24T18:28:00.011+02:00

I'm working on a project that uses Kinect depth camera to detect a person silhouette as I have mentioned before in this blog.

Part of the development was done using a Mac because I found a library that enabled me to use Kinect directly from Processing (which I've found very convenient for prototyping).

It did not hurt that an OpenCV library for processing was also available.

What was missing was a version of the Kinect's Processing library to be used with GNU/Linux. Fortunately, someone took the time to tweak the Mac version to make it work and to post the process online. It did not work for me exactly as it was but it was close. So just in case you want to experience with it, here are the steps that worked for me:

Get a copy of the library:

git clone git://github.com/shiffman/libfreenect.git

Create a and move to a build directory inside libfreenect folder

cd libfreenect

mkdir build

cd build

cmake ..

make 

sudo make install

Go to wrappers/java and edit build.sh file (remove -m64 compiler flag unless your platform is 64-bits)
Make sure the folders for libfreenect.a file and for the Java directory containing jni.h are correct in the build.sh file
Run build.sh:
```
sh build.sh
```
Make sure the step above was error free.
Now copy the folder openkinect from wrappers/java/processing/distribution to your sketchbook/libraries folder
Copy file libOpenKinect.so from wrappers/java/dist to sketchbook/libraries/openkinect/library/
Almost there, create a symbolic link in that last folder:
```
ln -s libOpenKinect.so libkinect.so
```
Fire up Processing IDE and try any of the examples from the openkinect library once you have connected your Kinect to the USB port.

Update: In case of trouble do not forget all the install details provided here.If you're using Ubuntu 11.04, the following packages need to be installed: git-core, cmake, libusb-1.0, g++, libxmu-dev, bixi-dev, libglut3-dev. If it happens to be a 64bit Ubuntu it won't work (I'm still figuring out how to make it work).

Fixed! In case you have 64 bit ubuntu, make sure your processing folder does not include java binaries (if it does, it'll likely be 32 bit, as it was the case with my processing 1.5.1). Once you're using 64 bit java, the 64 bit library created with the instructions above will work nicely too.

Fixing a broken compact-flash socket (sort of)

2011-05-09T13:49:00.004+02:00

A few days ago an incorrect manipulation of the compact flash memory broke my Canon reflex camera memory socket. It was a very bad moment as I was not able to use it in my recent trip to China.

Though I was able to get some thin tweezers I was only capable of breaking the bent pin. So my camera was useless now.

Once back home, I've tried a simple solution that worked nicely, so nicely I want to share it with you: I just took a strand of copper from an electric wire and I stuffed it in to the hole of the compact flash memory that corresponded to the broken pin. It created kind of a small copper wire brush that makes contact with the broken pin once the memory is inserted. It is a cheap solution to the problem that I've found surprisingly good.

If you have several broken pins you may try this, but I am not so confident you'll get a decent contact for all of them at the same time.

Wireless missunderstandings

2011-04-22T15:02:00.004+02:00

Though we bring an iPad to China, we ended up not buying a SIM card for it as we were told we could borrow one. But then the card we borrow was to be returned and we could not cut it down to fit into the iPad. My new Samsung Galaxy S could not accept the card as it was SIM-locked so we ended up using the SIM on our Nokia E71. Thus, iPad could use the GPRS access of the phone thanks to JoikuSpot software.

Unfortunately, the access JoikuSpot provides does not seem to work for the Galaxy S.

Another problem I faced was that the few wireless networks I can access are protected by a captive portal that, once a valid username and password is provided allow clients to access the Internet. My Eye-Fi Geo SD card performs the geo-location for my pictures but only if pictures are downloaded wirelessly to the computer. But Eye-Fi firmware did not support captive portal authentication so I could not use these wireless networks.

Unfortunaltey the Eye-Fi card cannot work with JoikuSpot either. A potential solution was to use the Galaxy S in the wifi router mode as then it acts as an access point. But again, the problem was that Eye-Fi manager software needs to have an Internet access through that connection in order to be able to accept this new network into the Eye-Fi card configuration.

I did not want to enable data roaming for the Galaxy S as prices are just outrageous (even if my company is paying the bill). But eventually I was forced to enable it for a moment till the card configuration was in process. Finally I can download wirelessly the pcitures to my MacBook using the Galaxy S as the access point. For that operation I can keep the data roaming off with no problem.

I reckon that Eye-Fi should have made life easier for their customers and not more difficult.

The other Great Wall

2011-04-20T12:29:00.004+02:00

Being in China for a few days is an eye-opening experience: both the future and the past are mixed together here in a curious combination. There are many good things beyond the food: A taxi driver may return your missing phone and the waiter will patiently wait for you to order. Other things are not so nice: don't expect queues to be respected nor all cars to stop at pedestrian crossings, even if there is a red light.

Internet experience is also special: Many sites just don't work. Others work like if something was wrong under the hood and finally, the rest work like in the rest of the world. It is not a problem of network speed (though some links could use some extra speed) but of the control the government imposes upon what can or cannot be browsed by citizens and visitors of China.

For some visitors like me, showing some pictures on Facebook for family and friends is a common activity when we are abroad. Not being able to even open Facebook or to make a blog entry (like this one) feels odd. Of course the reason is the so-called Great Firewall of China.

But this did not come as a surprise as I was expecting to have to deal with this problem. The common answer to this problem is to use a VPN connection to a server outside of China and to use that VPN server as the default gateway for all your IP traffic. Performance may degrade but you are free from the limitations of the firewall. However, what was a surprise was that the campus network did not allow VPN connections. Without a VPN my attempts to use this as a way to overcome the firewall limitations were gone.

Given that my original plan was a no-go, I had another back-up plan: to use a ssh connection to forward web traffic to a proxy outside of China. This is the plan that is working nicely now. I guess that other providers in China do not use to block VPN connections though.

Chinese language

2011-04-04T13:15:00.005+02:00

I am honored to have been invited by Beijing Institute of Technology and I am visiting Beijing in a few weeks and I have no previous knowledge of Chinese language.

Human languages, as many computer languages, are based on the use of an alphabet. But what if, like APL, you are not familiar with that alphabet? That would be the case should I try to learn Persian or Urdu languages.

However, Chinese language does not use an alphabet to build words with its symbols, but each word is represented by a logogram (ideographic or a pictogram or a composition of both). Learning a different alphabet has to be difficult, but learning a language based on ideograms looks a huge endeavor to me.

Of course I'm not claiming "I am learning (mandarin) Chinese", but I'm just looking at some of the basic ideas behind the structure of the language and I get the impression the task is not something easy to achieve for the written language. The spoken word is also challenging, but with the help of Pinyin system it might be doable for westerners with tons of practice (as some features like the tones seem an extra challenge).

When I have been to other countries in Europe or America, I could read the signs and bus line names even if I did not understand their meaning. Not anymore in China. There I am going to be not only illiterated (because I can't read or write) but also kind of dumb as I cannot ask others for information (as I do not expect many Chinese citizens to speak either Spanish or English). It is going to be quite an experience.

Galaxy S: a few months later

2011-03-25T17:25:00.005+01:00

A few months of use have given me some perspective on Samsung's Galaxy S. What I have liked is how easy it was to get Gmail working and configuration of services in general. But several things have been confusing and not so nice: for example the use of calendars or the contact lists. It seems you can maintain several calendars and there are different places where you can store your contact list.

The initial contact list synchronization was not easy as Galaxy S won't work with Apple's iSync. I used SyncMate application but I did not like either. But I can recommend Dropbox as it is a great tool not only to get content onto your smartphone but also to upload pictures from it.

While a do like Android, the system has a lot of room for improvement, the worst thing is the variability on the response time. Sometimes the system is just not interested on what you do. You may get a call you cannot answer for a few seconds because the system is busy doing something else. I do not like that at all.

Another annoying security feature is that access to phone files via Bluetooth allows you to access they filesystem but all folders appear empty. You need to enable BT-visibility file by file. Not the best way to read your photos. And speaking about photos, I was not capable of pushing pictures via Bluetooth. Linux and OS X refused to accept any file from my phone using this method.

Multimedia support was good out of the box and the phone was happy with any AVI file I drop at it, and for that purpose, the microSD socket is the way to go, as it is to have an easy to replace battery.

Firmware upgrade from 2.1 to 2.2 showed some improvements in response time and battery duration. But I still need to charge the battery every single night (remember batteries have a limited number of recharge cycles).

On the plus side, I've found the phone to have good sensitivity (better than iPhone 4) and very good voice quality and an ok handsfree operation. I do not regret my decision and I would buy it again, but I will be happier when some of the not so nice details are gone.

By the way, the worst "demo effect" I experienced when showing the phone to an iPhone owner was that pictures taken did not show up in the media gallery. I had to reboot the phone for fixing this. My friend was, of course, not impressed about the Galaxy S.

The rise of plug computers?

2011-02-28T16:59:00.003+01:00

A while ago I invited an old classmate over to give a talk on campus. He is working on a new project called Amahi. It is a Linux-based server software. But instead of aiming at the regular PC --maybe the old computer you might have at home-- they are focussing a relatively new breed of computer that some have called "plug computer". But ... what is a plug computer? They are small low-power headless computers that are built inside a power supply. Usual connections are USB ports (to enable external storage or other peripherals) and Ethernet network. These computers do not have a hard-disk drive but a small flash-based storage on board.

What these plug-in computers really shine for is as home servers. They need a really small amount of power, usually less than 10 watts, so keeping them on 24/7 is not going to have an impact on your utilities bill. The compact size and silent operation open up many interesting applications (ie. media server, download server, personal website server, etc).

The unit I am testing is called guruplug and it includes Wifi and Bluetooth wireless connections. It is powered by a 1Ghz Marvell's ARM CPU and it uses 3.5 watts while streaming flash content over wifi. A JTAG interface can be used to write a new system image on the guruplug.

I'd say the future format of the entertainment system around the TV set is not clear (at least not at my home). Some modern TV sets do have an Ethernet socket enabling media streaming (ie. DLNA) and others may also handle YouTube or Netflix without additional hardware. Other manufacturers are selling Blu-Ray players that include plenty of streaming features (ie. LG BD570) to be connected to a [dumber] TV set using HDMI socket. Streaming companies operate only on certain countries (ie. Netflix is not available in Spain), so they are not always a choice. And both Apple and Google have their own offerings (ie. Apple TV and Google TV). It is going to be interesting to see how this market develops.

Annoying Java behavior

2011-02-21T19:55:00.007+01:00

A recent class exercise required students to create a program that handle a list of scheduled events. While I was not suggesting a specific approach, I used java.util.Date for handling the time.

Events happening in the future can be scheduled by adding a certain value to the current time. System.getCurrentMilis() gives you the value of milliseconds since January 1, 1970 00:00:00 GMT.

When creating a new Date object, the default value is the current time, but any number of milliseconds could be used to create any time into the past or the future. I was using this approach for scheduling future events. Later, I was checking, every second, if any of the future events on my list was already due. Unfortunately, I was using .equals() function for that but only a few times worked as expected.

The problem was that .equals() function works on a millisecond time base. If the two values compared are not exactly the same number of milliseconds since January 1, 1970 00:00:00 GMT then the answer will always be false.

If you are like me, you might be expecting two dates to be the equal if date, hours, minutes and seconds are the same. The simple solution is not to compare the two Date objects but the strings you obtain with the .toString() function of each one.

This site also seems not happy about Date class.

It is the Android year!

2011-02-03T20:45:00.005+01:00

Well, I might be wrong but apparently Android shipments just overtook Symbian platform during the year 2010. I have been using for quite a while a Nokia E71, which I can wholehearted recommend, but I was told by my carrier that it was time for a change.

Of course the question to iphone or not to iphone was raised. Owning five different Apple computers over the years plus an iPad seemed to make me the obvious iPhone customer. Did I tell you we have our own share of ipods, including a couple of iPod touch? However, after buying our iPad it became clear that the way Apple wants customers to behave and use their expensive devices was not very customer friendly. I really hate to have to use iTunes to just add a file to my iPad (thanks Dropbox to make my life a bit easier here). And I find despicable that once I have sync my iPad to a music library I have to lose everything if I ever dare to try to sync with another of my computers at home. I am sure that Apple can make a long case about how they worry on enforcing the copyright owners rights, but as the owner of my own iPad I strongly object against that. So much that I bought an Android phone instead.

Unfortunately, Google Nexus S is not yet available in Spain. I was having a googler from the UK office coming to my city for a talk and I was tempted to ask him to bring one Nexus S from London, but finally I settled with a Samsung Galaxy S from which I have heard several praises from some of my colleagues. In the last minute I double checked with another colleague who owned a Nokia N8 but he was not happy so I made my move.

After a few days of use I'm quite happy with the Galaxy. It is lighter than the E71 and quite slim too. The screen is large and I like it very much: colorful and bright. And, as most of the smartphones cannot stay away from a charger for more than a couple of days (though daily charge is the way to make sure you won't run out of juice unexpectedly). The use of microUSB charger is nice and I can keep the power mains charger at home and the USB charging cable at the office.

Both Google goggles and Google Translate apps are interesting enough to have at least some fun. But Skype app proved to be a disappointment as it refuses to work. The technology that I think it is missing in the Galaxy but present on the Nexus S and it is presumed to be on iPhone 5 too is the NFC (RFID) interface.

Update: One successful upgrade later, I'm running Android 2.2 on my Galaxy and it feels more responsive, battery lasts longer and Skype works. In the mean time I can see there is a new Galaxy S II from Samsung that looks cooler than Galaxy S and Nexus S (and it includes NFC interface too).

And regarding my Android experience, so far so good. I have found lots of interesting applications for my phone, including the Wifi-Analyzer. And the phone keeps on working no matter the way I hold it in my hand. But, as expected, you need to recharge every day.

Roomba: It does the work!

2011-01-30T18:44:00.004+01:00

This year we've got for Christmas our very first home robot. I was a bit reluctant to buy an expensive item just to figure out later it might work elsewhere but not at our home. This has not been the case. Since day one, our Roomba performed nicely and the only trouble we've got is that it does not like our low-profile doorstoppers.

We've made the comparison between them amount of dirt picked up by us and the one we remove from Roomba. I've to say the robot wins in the "who picked more dirt" game. The only extra work we're doing in preparation for Roomba to clean a room is to remove as many objects as possible that might interfere (i.e. chairs, trash bins, etc). I'd say it's been money well spent (as far as the robot keeps the performance level for a couple of years).

What is a plus is that the robot may return to the charge station by itself (sometimes) when battery needs to be recharged. I'd day this is not a feature to trust on, as I'm afraid it may not work in some cases. Apparently if it detects the proximity of the recharging station while the battery is low, then it will go to be recharged. But I won't say it will actively try to find the recharge station by roaming around the house. That means that sometimes Roomba may just power itself off somewhere in the house after doing its job for quite a while (I'd say it may run for more than an hour before battery is depleted).

We all find amusing just looking at Roomba do the cleaning and, even more interesting is the docking process (the return to the charge station to be recharged). The not so good point is that is noisy: You do not want to have in the living room when you're watching TV.

Geo-tagging with Canon Powershot S95

2011-01-18T21:00:00.005+01:00

No, geo-tagging is not a built-in feature on Canon Powershot S95. However, there is an interesting technology for doing that with your favourite camera. I was introduced to that three years ago by googler Mano Marks (of AppEngine fame) but I was not too impressed at the time (as I was not sure how to store that info). However, once I started using iPhoto I saw that application was aware of geo-location information and therefore it could be useful to have it in my pictures. This Christmas I've got a 2GB Geo Eye-Fi SD card as a present. I'm happy to report that it works nicely with my Powershot S95, where each image is shown as uploaded or not uploaded by means of an icon (Eye-Fi cards can wirelessly upload your pictures using wifi networks).

Uploaded images contain geo-location information, so when you import them into iPhoto they will include location information on where each picture was taken. This cards use the same Skyhook database used by other devices to pinpoint location based on the available wifi networks nearby. Therefore, you get no useful information when you are on the forest or dessert (as there are no nearby wifi networks there). This system is ok urban areas though.

And the beauty of it is that you can use it your existing camera as far as it supports SD memory cards (or compact flash cards, as there are adapters available for that too). Ranging from $30 to $190 these cards are more expensive than regular SD cards, but the extra features may come in handy. Please note that the feature set of each model is kind of tricky, so make sure the card you're buying performs as you expect (i.e. only Pro models will wirelessly upload RAW files).

Update: For reasons I did not understood all the pictures taken on a trip did not get any geotagging. In some cases I was positive it was an area rich of wifi networks. What was wrong? Well, eye-fi cards need to be powered on for a while before they can geotag. If you, like me, power the camera off as soon as you're done taking the picture and you do not power it on many seconds before the first shot there is a chance you won't get any geotagging at all. Card manufacturer says that the longer the card is powered the better chance your picture be geotagged (bump). Given the fact that eye-fi cards are much more power hungry than regular SD cards this "desired" usage pattern will have a big impact on battery time.

Powershot S95 has a good handling of this card, showing useful icons on the display to inform you when there is wifi activity and whether each photo has been uploaded or not. However, a second dissapointment has been the poor coverage of the Eye-fi card once inside the S95. I need to move the camera to the same room where my access point is for pictures to be uploaded to my computer. Transfer time could be better too but I'd say it is acceptable.

Yet another source of disappointment is the fact that location information is ignored if you take the card out of your camera and plug it in your computer. Location information is only ok if the image file is wirelessly uploaded to your computer.

Finally, the last nail in the coffin is the fact that Eye-Fi tells you to shell out more money if you want to upload your pictures to any on-line service (like Flickr or Picasa). It seems the 'x2' versions of their cards do include a lifetime free service but not the 2GB Geo. So the only free wireless upload is to your own computer and, while they say they are iPhoto compatible, uploads won't happen to your iPhoto library automatically. You need to import the pictures from the upload folder to iPhoto application.

Because all of the above I cannot recommend this product or technology. It is a good idea but I am not happy with the final result. The worst part is that you only learn location information is missing at the very end of the process (once you've imported the pictures to iPhoto).

Silhouette extraction algorithm

2011-01-05T16:29:00.009+01:00

As shown in the video above I have been working on an algorithm to extract a person's silhouette for an arts installation I am working on. The main idea is to use the depth map provided by Microsoft's Kinect so only a small range of distances are used to identify the person standing on a certain spot marked on the floor. By discarding those pixels that are too far away and those too close what is left is the person or other obstacles placed a that desired distance from the camera.

It is a bit tricky to make depth and RGB cameras to match exactly the same image (as they are located a few inches apart) so video shows some discrepancy between the dancing user and the drawn contour line.

Code was written in Processing using Daniel Shiffman's kinect library for Macs, OpenCV library and MovieMaker library to create an output video file of the action. In the mean time I was developing this, Daniel updated his library and some changes were needed. Unfortunately, OpenCV for Processing only includes some functions and simplifyDP was missing, so I was forced to implement my own version of Douglas-Peucker polyline simplification algorithm.

At last, Canon S95 RAW format supported on Snow Leopard

2010-12-18T19:14:00.002+01:00

It's been half a year since Canon PowerShot S95 appeared. Today I'm happy to learn that together with a software update to the "crashy" iPhoto '11 comes a software update for new cameras on Snow Leopard.

Playing with Kinect

2010-12-16T16:08:00.005+01:00

I was learning OpenCV for a new art project, but then I learned that the new Microsoft Kinect device had been hacked by a Spanish student after the bounty offered by Adafruit Technologies.

This news changed it all, as Kinect drivers for several platforms were made available. I needed to extract the silhouette of a person from the exhibit space and having a depth image as the one Kinect provides made my job ten times easier. The previous plan was to keep an image of the background and substract the current frame from it to detect changes. But handling changes in lighting conditions was a bit challenging.

What Kinect provides is a regular color (or infrared) webcam plus a second camera that measures depths (ie. each pixel brightness represents the distance to the kinect of that scene point).

If you want to isolate object from an scene that are at a certain distance from the camera, all you need to mark those pixels between a certain value range on the depth image. Simple, fast and highly effective.

Most of the work has been done using OSX and openFrameworks (an open source framework for interactive applications).

Untitled from Miguel Sanchez on Vimeo.

How not to buy from Dell

2010-12-01T18:41:00.011+01:00

I had some funds to kill and I thought a new small laptop running Windows 7 would help me not to be a total illiterate when it comes to whatever changes come with W7. I wanted to replace my old Acer Travelamte 3002 WTMi that served me well (though loudspeakers failed almost from day one).

A quick look around the web showed that Dell M101z model could be a good choice: good value, acceptable battery time, small and not too heavy. I've never bought from Dell before but I guessed it won't be difficult or unpleasant: I was wrong.

First of all, I wanted Dell to produce an invoice to the name of my employer. I contacted with Dell chat (sorry, not available over the weekend) and I asked them for help. I was provided an email of a Dell representative dealing with my employer. I sent her an email and waited.

After 24h with no answer, I contacted Dell chat again asking how long should I wait to get an answer, as this being my first time with Dell I was not aware of what the typical service delay figure might be.

I was asked (twice) for my phone number and email and a sales person rang me. However, when I informed him that I wanted this sale to be billed to my employer I was told only the person I emailed before could help me. The salesman [kindly] made some checks online and told me I would be getting a response by email that same day. He was right, a few minutes later I received an answer from my "designated Dell representative".

News were not good though. In a one-line answer I was told the model I wanted to buy was not in the representative's list. That was, perhaps, a model to be sold for home users but not to business customers.

I was surprised that no alternative was provided, maybe an alternative model with somehow similar features, or the advice of buying the unit not as a business customer. Well, maybe things are done differently at Dell.

Anyway, I had researched the topic quite a bit and I was still convinced that model was a good deal, so I emailed back stating that I had no trouble paying credit card (instead of my company being billed) as far as I could end up with the laptop and an invoice to the name of my employer.

Once again, I was told what I wanted was not possible. Ok, it seems it is time to give up. Maybe this is the way they work.

So then I went back to the web, and started searching for alternatives. I learned that Hewlett-Packard had a small laptop line called DM1-*. I saw several models on Amazon that looked ok.

But then I was surprised that, when looking at the same HP model in PC City, they were selling Dell M101z there too.

I've bought things in PC City before and I am positive they can produce an invoice to the name of my employer (although they will want me to pay cash or credit card). So, just by chance, I learned how I could buy a Dell M101z and get an invoice to the name of my company. Nobody at Dell figured that out for me, even when that was exactly what I was asking for.

Now I am not sure I'm buying that model from Dell as I try not to favor those companies that do not treat me well as a client.

In these times of economic hardship, it is difficult for me to understand how companies can be so insensitive about their customers needs.

Update: I ended up buying an HP DM1-2150ss laptop instead of the Dell one. It was available at the same price as Dell's but I was not happy with the way Dell had treated me as a prospective customer. HP model was lacking Bluetooth though.

I bought it in PC-City but I cannot recommend them either, as I went through a small nightmare trying to reserve it online. Just to find out later that my on-line reservation served no purpose once I told them I wanted an invoice to the name of my employer. They do not seem to care much about their customers either. I've got my invoice eventually, but it was not easy nor pleasant to deal with them.

OpenCV with Processing

2010-11-25T17:17:00.003+01:00

A recent art project requires to do some image processing. This topic is a bit away of what I use to do so I asked around what was available now. Some people suggested me to use OpenCV, which is an open library for Computer Vision projects.

I realized that Processing also had some basic features for real-time image capture. Even better, I learned that there was a version of OpenCV available for Processing.

The reason of using OpenCV from Processing instead of directly programming in C++ is the easy setup you have with processing. If you have a PC or Mac the use of the system webcam is very easy. For Linux systems it is slightly more complicated.

OpenCV makes very easy to do thinks like detecting faces on the image, which is quite funny. There is this book about OpenCV too.

Dropbox experience

2010-11-10T19:14:00.006+01:00

Once I realized I needed to sync my iPad to pass every tiny file to it though iTunes I was not happy. So when I learned there was a Dropbox version for it that was free I saw an opportunity. Later, I found out that there were dropbox versions available for Linux, OSX and, of course, for Windows.

A bit later, I learned that even there is an app for my trusty Nokia E71 so I can upload picture to a dropbox folder right away.

Since then I've almost stopped using a USB pendrive in favor of dropbox and till now, the server has been great.

In a nutshell dropbox is a shared folder on the web plus an app on each computer that syncs the content of your local folder with the copy held on the Internet. Any file you add or change is modified on the network storage. To put the icing on the cake there is also a web-based access to your data, so if you're visiting a friend or using a lab computer you cannot install software on, you still can access your dropbox account files.

Basic service is free (2GB storage) and there are fee-based accounts for larger data needs. If you don't have an account, you can use this link so you'll get 250MB extra storage and so will I.

Update: Today's system upgrade of my Ubuntu Karmic complained about the key of dropbox package, so it cannot be updated. Here is what you need to type to get it upgraded properly:

sudo apt-key adv --keyserver pgp.mit.edu --recv-keys 5044912E

Java and Javastript playing together

2010-11-03T17:56:00.003+01:00

One of the features that came with Java 6 is this neat trick: You can have a Javascript runtime on your Java program. You feed it with Javascript code and you can get the value of the variables.

It looks great if you need to use some logic already encoded with Javascript and you need to include it in your Java program. No rewriting is needed then.

I've done a sample program to evalaute a simple arithmetic expression as the first command line parameter of this Java program.

Save yourself some trouble with iLife'11

2010-10-25T12:30:00.005+02:00

Just for testing it I installed the new iLife'11 on one of my systems. I mostly use iPhoto and I was happy with iLife'09. What I can see now is that iPhoto look has changed to be more similar to iMovie on the user interface. Some floating menus (like photo adjustment) are not embedded on the application window and general look is worse IMHO.

But this is not the only problem. Calendars are no longer available on iPhoto, so it seems they will be back soon.

The worst thing, however, happened when I was using the new iPhoto: Suddenly my system stopped responding to mouse click or keyboard. Pointer still moved with the mouse but that was it. I suspend the system and when restarted I've just got a blue screen. I power it off by holding the power button for a few seconds. On the next power up they system asked me if I wanted to send a report to Apple, which I did.

Whether this was caused by the new version of iLife or not, I do not know. But my system has been running rock solid for several months, so I'd guess iLife'11 is the more likely cause.

The bad news is that you cannot easily go back, to the former version of iLife as your photo library has been converted to a new format. Apple: this is just insane. I'm not sure I want to use time machine to go back in time to get this as it was before (not sure if it will work nicely).

So my advice with iLife'11 is for you to refrain from updating till Apple irons out all the wrinkles of this release. I'm sorry I'm not mentioning other programs of the suite, like Garage Band that I guess has got an important face-lift, but it is not a program I use.

Update: A few days ago I've got a software upgrade for iPhoto'11. Since I reported my machine hanging once while using the new iPhoto I've got not the same problem again.

Update Nov 9th: I've finally got the update and calendars are back on iPhoto 9.1. No other freeze of my computer has happened besides my intense use of iPhoto lately. AVImporter errors with some movie files from Canon cameras have stopped happening, so there is an improvement here. Still waiting for Apple to support Canon Powershot S95 RAW format.

Update Nov 14th: After importing some pictures and browsing them on iPhoto my system stopped responding, again, no response to any keystroke while mouse pointer still could be moved around. I left the system alone for a while and when I was back it had a kernel panic sign. I'm afraid there is still something really wrong in the new iPhoto. We're going downhill the Windows way :-(

Multi-flavor remote access with TeamViewer

2010-10-23T17:46:00.003+02:00

Remote access is a cool feature, whether you are (still?) using telnet to remote desktop protocol it is something that is very useful. If you are like me, from time to time you get a phone call from a friend asking for help. Of course her explanations hardly match what you picture in your mind, so many times you cannot help them.

If you plan on supporting someone online you can install and configure the computer and networking gear (broadband router?) so you'll be able to connect to that system in the future when there is trouble.

Many different solutions can be used, but most of them are OS-dependent. You can do lots of cool things with SSH but mostly on a Linux or OS X system. Microsoft includes the RDP tool for remote desktop access to Windows computers.

I've heard about TeamViewer before from a client, but given it was a Windows-only solution I did not pay many attention at the moment. I've recently learned that many interesting choices were available: iPad & iPod version, Linux and OS X versions were developed.

Besides being a multiplatform remote access tool, it has another cool feature in its bag of tricks: It works through a firewall or a NAT box. That means you friend does not need to mess with her broadband router (huh?) anymore for you to be able to connect. Users get a client ID and a random password they can tell you over the phone/email for you to connect. You can see their screen and control the remote system, exchange files or use the built-in Voice over IP chat tool. Communication is encrypted too. And being free for non-commercial use does not harm. Client ID is just a nine digit number, no IP addresses that are weird for many users.

I just am not sure how useful the iPhone version could be.

Prototyping on the cloud

2010-10-14T17:56:00.003+02:00

I recently learned about an embedded design contest jointly organized by Circuit Cellar Magazine and NXP and mbed.

I signed in and I've got lucky as I've got one of the free development units. Having used Arduino platform before I was curious about how easy this thing would be.

Fear no more, I was setup in a moment. The funny thing developing with mbed is twofold: On the one hand, your computer will see a new flash storage drive when you plug in mbed. On the other hand, no compiler is installed on your computer. Instead, you use the mbed web. They host the compiler through a web interface. Once your code is compiled you just download the binary code to the flash drive and (now Arduino fans can smile) you manually press reset button for your code to be run.

I guess many complaints can be made if you dissect the service EULA, but definitely this way of working comes with many advantages too. Being multi-platform is not one of the least important ones.

Now I have to think about what could be a decent contest entry to make some cash :-)

Snow Leopard on your favourite virtual platform

2010-10-07T14:04:00.003+02:00

I've been using computers for quite a while and one of the things I like is to play with them. Since Apple moved away from PowerPC processors to Intel x86 processors many people thought we will soon have OS X on our PC hardware. Being Apple a hardware company, they have few reasons to make that happen (or so they think and act upon).

A few attempts from small hardware manufacturers of offering hardware that allows the install of OS X have faced a lawsuit that more or less kicked them out of business.

Some other people just made that same thing just for fun. What they call hackintosh computers are PCs running OS X that has been install after a more or less "hide and seek" game with several DVDs.

You need determination and the right hardware to get it working. Many times, a software update prevents your system to boot up next time. As a challenge it might be fun, but there is no fun on discovering your work is buried inside a system you can no longer boot-up. So the use of this hackingtosh computers may not be recommended (some even claim it might be a breach of OS X EULA, which does not allow it to be installed on non-Apple hardware).

As we have several Apple computers at home, I do not have a big incentive on running OS X on a PC, but I've always found it an interesting proposal. I've tried to install it on several old computers without luck. But yesterday I tried this simple steps to get it working on VMPlayer and it seems to work nicely (once I managed to change the locale to Spanish/English instead of the original Russian of the virtual machine image).

Any magic on the new Apple touchpad?

2010-09-24T17:36:00.002+02:00

I liked the idea of a new tracking device. I guess some time using the iPad gave me the wrong idea on what it could feel like to have a similar interface as a mouse replacement.

The same day I received an email from Apple stating the new Magic Trackpad was available I rang a local shop to see if they have it. I was told that because it was announced today they did not have it. That I should wait a few weeks before they would have it. Weird.

Anyway, after the summer holidays I wanted to switch one of our iMacs to wireless keyboard and mouse so after being turned down in one Apple shop (a different one), where again I was told I will still have to wait an unknown amount of time (not very helpful direction). Hopefully, I stopped by a third shop where I bought a Bluetooth keyboard and a Magic Trackpad.

Trackpad is ok but not magic. For the same money I would suggest anyone to go for a Magic Mouse. It is not that the trackpad does not work, but I've found much more convenient to use the mouse.

Bye S90, Hello S95

2010-09-07T13:45:00.005+02:00

The Canon PowerShot S90 I've bought a few months ago had a problem. I had to sent it back to Canon to be serviced. I was unlucky and after more than two months waiting I complained to Canon.

It transpired that a new part was needed for the repair. My long wait was rewarded with a brand-new PowerShot S95 instead.

Even the seller (I bought it on eBay) was so ashamed about me waiting that long that gave away a 4GB SD memory too.

Have a look at this analysis.

Plastic Logic bites the dust

2010-09-03T22:11:00.004+02:00

I was very excited by what this company was about to deliver. But unfortunately they have cancelled the launch of their QUE electronic ink device.

In the mean time, Amazon and Barnes & Noble get into price fight that drove down the prices of their entry-line ebook readers to around $140. This is around halve of the original price and what is better, more features are added to the new devices (ie: wifi).

I really like the new Kindle 3 and over the summer I've been reading a lot on my 6" Papyre ebook reader. I've come to the conclusion that 6" is more convenient than the larger size of Kindle DX for reading novels. I'm kind of disappointed with KDX as it is not good for letter-size documents (or A4-size) in my opinion.

I've used a lot our iPad over the summer but just for browsing and, more importantly, to use the Maps application to find where to have dinner or to look for the route to a destination (very handy when travelling). However I've read not a single book with it (though I loaded a bunch of them just in case). What is worse, I've learned that some of the PDF files I've loaded on iBooks completely crash the application once opened. And when this happens the only way to get iBooks to work again is to remove the offending (opened) PDF file from iTunes and to re-sync the iPad . If not, every time I open iBooks it goes to the same PDF and it crashes iBooks before I can switch back to the library view (Mr. Apple, please fix this soon).

In the ebook market in Spain, vendors seem to believe they still can keep prices as they were last year (around 250€-ish) regardless american vendors have halved the prices. Should I were about to buy a 6" now, I only would consider a Nook or Kindle (because of prices and features). While happy with my Papyre I can see the new Kindle has many improvements.

Kindle DX update blues

2010-07-27T20:17:00.005+02:00

A few days ago I received a letter from Amazon stating a new firmware was available for Kindle, and that those with coverage problems with Whispernet could get the update file from the web too.

Firmware update for Kindle is supposed to be quite a straightforward operation. First, update file is downloaded to your Kindle, either wirelessly or manually by the user, to the main folder of the system. Once in there, either because user request or automatically, update process starts.

I've done this before and no trouble happened then. This time was different, though. I mentioned on a previous post that I've played with the USB networking hack, that enables network access to the Linux system running in the Kindle. I did some tests, set the correct system time on my Kindle and forgot about it.

Now that I was trying to update from version 2.3.4 to the new 2.5.2 version I was stucked. Update process stated normally, and "stage 1 of 3" was shown on the lower right corner of the display, but a few seconds later the process stopped with an error message and the error code U006 was shown on the lower right corner.

Several minutes later it was clear the problem was due to a checksum error of one of the system config files. I vaguely remember I did some minor changes to several files, but months later I could not remember what I might have done and to what files.

Luckily there was a way to find out where the problem was. System logs are accesible by the debug command ;dumpMessages that will create a new "book" with the contents of the log file. A careful reading of which led me to discover the file causing the trouble was framework.mario.conf.

Again, thanks to Mobilread forums I've obtained the original file, that though did not have the expected MD5 sum, it worked flawlessly. It is a shame the whole process took me a couple of afternoons to figure out.

I guess the moral of the story is that if you fiddle with your Kindle´s internals, please backup any file before changing it and keep a clean record of what you did.

Prepaid data plans in Finland

2010-07-25T18:40:00.007+02:00

I've been researching the topic of how to get prepaid data cards for an upcoming trip to Finland. It is said that Finland is one of the cheapest and most competitive wireless communications markets.

Contrary to most people, I just need a temporary solution to get our iPad working while on the go. While most hotels and cities (i.e. Oulu) do have free wifi, I was looking for an alternative to the outrageous roaming cost of Movistar (from 4 to 10 EUR per megabit).

Saunalahti offers a seven-day 4 Mbps data plan for 6.90 EUR. I thought my problem was solved. But just in case, I asked customer service. I learned two things that were a problem:

In order to activate the card an SMS had to be sent. Unfortunately, sending an SMS is not one of the things Apple decided you're entitled to do with your iPad.
Saunalahti is reserving microSIM cards for contract customers, so if you want pre-paid and microSIM you're out of luck with them. (Apparently you might get lucky in an Elisa shopit, but this is uncertain).

It appears that my best shot is to get a regular SIM and to use this, for cutting the SIM once I've sent the SMS with the card using my cellphone. I've tested the cutting sheet with an old SIM and it seems to work ok.

If you think I'm missing anything, please let me know.

Update: Now that I'm back from Finland I can tell you that almost everything worked as expected (not that I was expecting that parking ticket though):

Saunalahti prepaid worked nicely, but there was a bit of misunderstanding on my side:

SIM cards are not data-only. You can buy the SIM card in R-Kioski in Vantaa airport for 6.70€. This card comes loaded with 4.90€ of credit (you can use them for phone calls, SMS or data service).
There is a weekly data plan for which you'll need to send an SMS. This plan will give you unlimited data for 7 days costing 6.90€. Please note in order to use this you'll need to add credit to your SIM (remember it comes preloaded with onlyt 4.90€). Again, you can easily add credit at any R-Kioski shop (very easy to find anywhere). Minimum credit increase payment is 10€.
Cutting the SIM worked nicely for my iPad. APM=internet, empty username and password.
No need to send any SMS unless you want to select a data plan. It was not point for me as there is a daily limit on the credit decreased each day due to data service of 1.80€. That means that you can have more than 8 days of service for your iPad for just 16.90€. (You can get eleven days of data service for the same money by sending one SMS message, but if you've already cut the SIM it may be difficult to fit it back on your phone unless you have an microSIM adapter).

Coverage was good but not perfect. Sometimes I lost connectivity while on the road, but it was not big deal for me. Having iPad's maps application on the go was great whenever we wanted to find a place to eat or as city map.

iPad and PDF magazines

2010-07-16T17:48:00.004+02:00

I'm a subscriber (and sometimes an author too) of Circuit Cellar magazine. I use to buy it in print format but a few years ago they made the switch to electronic format. Despite the well-know blues about piracy, they chose PDF files with no particular DRM built in. Since then I'm a paying customer.

While I was disappointed with the way the PDF was rendered on Kindle DX, I'm happily surprised that the magazine looks quite nice on iPad. And given the zoom capabilities and the instantaneous response of the device to pan actions I can say it is a very nice experience to read the magazine with it. The only caveat is that sometimes it freezes for a while when browsing the pages quickly. I guess it takes a while to render next page and iPad has limited both computing power and RAM memory.

How to get the PDF file on the iPad is also not obvious. Though there are several PDF viewers for iPad, the ones I've tried do not allow me to add the files I want to view. However, iTunes software will allow you to "Import to the library" PDF files containing magazine issues. One synchronization later the issue is available on the shelves of iBook application. (If you do not have iBook, just download it from iTunes store to your iPad). Happy PDF reading!!

Update: I've experienced several times a crash on the PDF reader while reading. iPad was not frozen, but I've heard complains from other people that their iPad froze while reading a PDF. Now I understand why there are so many different PDF reading apps for iPad. Still, I'd say iBook is kind of usable for me (mostly because it's free).

My wife has got an iPad

2010-07-11T17:45:00.005+02:00

I've been reluctant to give in to the latest Apple gizmo. I tried it out last week and it was ok. Web browsing was smooth and comfortable till you reach a flash based page (flash does not work out of the box). The best feature I noticed was that it dos not get hot. This is very nice when the weather is hot.

Writting tris entry using iPad keyboad proved not to be very convenient, as many words get replaced by others guessed by Safari to be what I want to write. Maybe it is causes by a mismatch between my localization and writing in English here. A simple post like this took me ten minutes and lots of backspace.

Getty Images Settlement Letters in Spain too

2010-07-02T10:22:00.003+02:00

Apparently, Getty Images is a company that sells stock photos. The same company you can accept on Flickr to represent your photo portfolio.

As such, it is believed Getty Images make they money by selling stock photos to their costumers, either end-users or designers that use them on their customer's projects.

As any other company dealing with intellectual property, they may have copyright infringement cases every now and then. But here is where the innovation comes: Instead of sending a cease and desist letter to those believed to be infringing upon any right owned by Getty Images, they will just send a "settlement demand letter". The whole purpose of that document is to (1) notify the alleged infringement, (2) to act as an invoice for the amount they claim it is worth the damages for the
previous use of the infringing images (3) to provide erroneous legal claims to confuse addressee (4) to rush recipient to pay without a second thought (5) to offer the licensing of the images to be used in the future.

A law firm contacted me a few days ago as they have received such a letter from Getty Images, London. As many other histories I've found on the Internet, this firm hired a web designer to create their website. That work was paid for and assumed to be correct and lawful. It seems Getty Images is sweeping the Internet with some software that collects images and checks whether they contain any of the images they license or not.

A 2.500 EUR invocice was attached to the letter as they claim the alleged "losses" where worth. My advice to that firm was to file that letter permanently in the trash bin and to remove the images from their website.

At no point in the letter were presented any proof of ownership of the "infringing" images to the recipient. For an asking price of 2.500 EUR I think they could do no less.

I won't be surprised if that were the work of a con artist. But as I have researched the topic a bit on-line I think it is actually Getty Images doing this to themselves, which I think it is unfortunate.

Unexpected treat

2010-06-22T13:28:00.009+02:00

Now that the classes are over and I'm thinking about a summer trip I've got myself a new camera. Two years ago I was impressed with Panasonic DMC-LX3 camera but I did not buy it as I've just bought a DSLR by then.

Last night I was checking prices on eBay and I saw a good deal for a Canon S90. I checked its features and it turned to be Canon's answer to Panasonic's LX3. It also has a nice F2.0 lens with more zoom than LX3 (28-105mm), a 10 Mpixel sensor and a nice 3" display. It has plenty of manual control and a myriad of shooting modes too. And it is compact, a bit more compact than LX3. I was not planning on buying it but apparently nobody else was interested on bidding and below $300 it was a steal.

My first experiences with the camera are good. Not really sure about the best way of holding it as it is quite small. The worst part is the wrist strap that does not seem to fit nicely.

She will explain all the basics better than me.

RGB color matrix project

2010-05-28T09:50:00.005+02:00

This project is a 5x5 RGB color matrix controlled by an Arduino processor. However, I've used my own RGB controller I mentioned on a previous entry of this blog.

Being controlled by serial communications I was able to develop the project on a computer and to try the different light patterns (I used Processing for this). Later, I transfer the code to an Arduino (Processing and C++ syntax are quite similar so it was easy to adapt the code).

Details can be found here.

Testing Chrome on Linux

2010-05-26T12:01:00.003+02:00

In case you didn't know, OS X and Linux now have Google's Chrome 5.0 browser available. My first impression was good till I was writing this post. Then, an oops screen was shown while editing this message with Blogger (I think it was when switching from HTML to preview mode).

Anyway, browser seems to work nicely. It seems fast, imported nicely my password database,bookmarks and digital certificates from Firefox. Flash worked ok too. I've only got a minor problem with Vimeo videos that do keep the browser window on top of the full screen video when switching to full-screen.

Optical tweezers

2010-05-25T00:47:00.003+02:00

Last time you used tweezers they were made of steel, weren't they? Well apparently there are "other ways". I think that a video will explain it better than my words. In the videos small (reflective) smoke particles are captured by the laser beam.

Google Code Jam 2010: Phew!

2010-05-09T12:49:00.004+02:00

I've just qualified for Round 1 on CodeJam 2010. I've found the exercises interesting but I was stuck with Fair Warning and I failed the large problem set for the Theme Park. Snapper Chain was the easiest (IMHO) as far as you saw the connection with binary numbers. One more year I'm ready to bite the dust on Round 1.

Update: Yep, as expected I failed to move beyond Round 1. I solved two first problems but failed the large data on the second because of my insistence to use int instead of long integers.

Animate the drawing of a SVG file

2010-04-29T17:40:00.007+02:00

Several times I've blogged about Inkscape vector drawing software and its many uses. Being free software there is nothing to lose if you want to try it out. I use it on Windows, Linux and OSX happily.

For a new project I wanted to get a given drawing animated and maybe with a soundtrack. My goal was to use this for explaining some topics of my lessons.

Long ago I saw LectureScribe and I liked it. But it was not exactly what I was looking for, though you might want to give it a try too.

What I am showing you below is a rough demo (no music so I won't get any damn DMCA notice; yes I know there are copyright free music). I've used a Python script by Ed Halley to get a sequence of photograms. Next I've used mencoder to combine them to create a video I later uploaded to youtube.

It's a drawing of an stepper motor interface.

In case you wonder, I captured this drawing using a Genius G-note board.

I lost my parallel programmer

2010-04-20T19:27:00.007+02:00

A while ago I wired a 25-pin parallel port socket with three resistors to build a parallel programmer for burning Arduino bootloader on brand-new chips. I used several times and it was great. However I do have the need to use it now and I cannot find it.

I've bought an ATMega328 as a drop-in replacement to have more memory available for a project involving the Ethernet shield and UDP networking. Unfortunately, Arduino Mega does not have the proper pinout for the Ethernet shield, so the ATmega328 is my best choice. But the new chip I've bought was empty and I need to burn the booloader.

I do keep my old PC available just in case, but my new iMac does not have a parallel port either. So I remembered that there was another way of burning the bootloader with some extra wiring on a Diecimila board.

And the wires go to the ICSP header ...

This way the FTDI serial chip can be used to burn the bootloader in the flash memory of the ATmega. However, it is not as easy if you are not using Windows. The problem is that in order to use this method, changes to avrdude program and FTDI driver are needed in OS X and Linux. The process is well documented but it is time consuming.

For those not interested on compiling away I'd recommend you to use a Windows virtual machine to make the process faster and easier. That's what I did and it worked nicely with vmplayer on Linux.

MicroRGB: A LED with a brain

2010-04-10T14:07:00.006+02:00

A recent project required to create a matrix of RGB leds. First prototype was set to a 5x5 matrix. For quite some time I've been thinking on the cheapest and more powerful way of doing this. Other people already answered the question in different ways. Either they put a micro controller on board, like BlinkM or they use a PWM shift register like ShiftBrite.

A while ago I learned of a website with several PIC-based projects in the same line, one of them it was a serial addressable RGB led controller.

One of the factors I was taking into account was cost. When you are using a large amount of units the unit cost becomes important if your budget is limited. I decided I wanted to create my own device. Should I chose a Microchip micro controller I could use the software mentioned above. My fist take was to use a 12F675 8-pin micro controller I found for $1 each on eBay. Unfortunately it seems too limited for the task of handling 3 PWM channels and serial communications as it lacks of a UART. Next stop was 16F628A that has more memory, timers and a hardware UART (and some code I can use is available too).

Next stop was to decide the format of the device: I was thinking of a small board that would hold a Superflex RGB led, the micro controller plus a programming interface (using SMD parts you program by soldering some temporary wires to the programmer is something I do not want to do very often). This way I am able to change the firmware to fit different applications.

Ok, so I have to create my own PCB for SMD parts. Well ... I've never done this before for SMD parts. After checking several software packages I settled with the free version of Eagle CAD that works happily with my Mac and Linux computers.

After some browsing I learned that Futurelc was making prototype PCBs at affordable prices. I sent them my Eagle files as they accepted that format too. Unfortunately something went wrong in the process as they remained unresponsive for two weeks. After that period of time waiting for them to ask me to pay for my order I decided I no longer wanted to deal with a company that treats you like this before getting your money (discovering this after you'd paid puts you in an even more difficult situation). I cancelled my order and I searched for another company. This time I selected PCBCART that also had good comments online and though more expensive than Futurlec hopefully would deliver my boards. Process run smoothly, they also accepted Eagle CAD files and a few days later I received the boards from China by Fedex. Please note that in order to keep my costs low I ordered a single-side board with no solder mask nor labeling. Therefore I cannot comment on how well they work in multilayer designs.

If you do not factor in your time, I'd say this thing can be built for less than $3 per unit. A typical setup just needs three wires (VCC, GND, TX) connected in parallel to all the units. TX line can be driven from a PC or an Arduino controller.

For programming the finished devices I used an old TE20X, which is based on the JDM programming interface for Microchip processors. The only problem is that you need a real RS-232 port on your computer (a USB adapter won't work).

Both schematic and board are available. And you can use Pete's firmware too.

Yet another laser cutter

2010-04-03T14:52:00.019+02:00

When my EPSON 830U decided not to work for me anymore (printing heads clogged) I thought I could make some use of the still working mechanics of the printer. It's based on a couple of stepper motors for both axis of motion (print head and paper feed).

So I replaced the original power supply and drive electronics for an arduino board and an stepper motor driver from Adafruit industries. Now I could move the printhead anywhere on a page. Next step was to add a laser on the printhead and to control it using a PWM output from arduino (so laser power could be modulated from the computer).

Though it only cut thin back color cardboard, it has may uses. I wrote a C program for arduino to control the stepper motors and laser. It receives data from the computer and interfaces with the old printer guts.

Data format is very simple: each line contains a sequence of integer numbers separated by blank space. Each pair of numbers represents one XY coordinate. Line ends with a CR (0x0d) character (that also shuts down the laser to stop cutting). First coordinate of a line sets the starting point (before reaching that location the laser is off).

I wrote some software running on my iMac that reads a Inkscape SVG file (only straight lines are supported though, use Flatten Bezier on curves to get a sequence of straight line segments) and translates it to the desired data format for arduino and it shows a preview on the screen. Data is sent through a USB port to the arduino. iMac code was written using Processing language (Java-based) so it can run on Windows or Linux too.

If you have an old EPSON printer, you may want to give it a second thought before putting it to the trash.

Video was shot by taping an iPod to the printer's head. That's why it looks laser is static and only cardboard moves.

Update: After I published the above version of software, I kept working on the next one. Now flow control works ok and the Processing code shows a red dot over the drawing while cutting. One click is needed to start cutting once the SVG file is shown and some minor changes make the code a bit better (SVG parsing code is very lame and failure prone, only straight lines are understood). SVG filename is still hardcoded in the Processing file.

The power of DVD lasers

2010-03-22T12:49:00.004+01:00

Next time you see a broken DVD writer unit, do not throw it away. It contains a powerful visible LED laser. Some lasers used for CD-ROM writers are infrared and, while powerful, the light emitted is not visible, making it both, staying safe and focusing it, more difficult.

In order to achieve some impact on a dark surface you need to give a decent amount of electric current to your laser LED (from 150mA to 300mA or more) and, besides, you need a lens to focus the beam. Focusing is important so as to concentrate the beam energy on a small spot (like you do with a lens and the sun light to burn a spot on something). If you are disassembling a DVD writer, you may look for the focussing lens too. If not, you can get one like this.

Some guys did make what they called a $50 laser cutter, sounds cool. I'm retrofitting an EPSON inkjet printer to do a similar thing.

Self-replicating machines

2010-03-10T22:21:00.006+01:00

You may have heard of Reprap, the 3D printer that prints itself, but if not, I'm sure it'll make you curious. The idea of 3D printers is that you can "print" 3D objects you've designed on a CAD program. Reprap printer or MakerBot are machines that can create 3D plastic objects by fusing plastic into small plastic spaghetti (that adheres itself while hot) over a movable table. Objects are created putting one layer on top of the other.

Given the fact that you can print 3D plastic objects, Reprap project went on to do design in such a way that a finished Reprap printer would be able to print all the plastic pieces to make a new one. Unfortunately metal parts and electronics still need to be bought elsewhere.

Care has been taken to provide open specification for all the components so anyone can build their own easily. Reprap first version was named Darwin (shown in the picture) but a new version is out, named Mendel, with many improvements, smaller footprint and better performance. The project however is a bit weak on detailing how to make your own Mendel if you do not have a friend to print you the parts.

Update: Well, maybe details on how to build Mendel are not so sketchy, but I failed to find them.

On addressable RGB LEDs

2010-03-01T09:11:00.004+01:00

I've been interested on the possible uses of RGB LEDs for quite a while. The underlying logic is pretty simple: Pulse Width Modulation can be used to control the luminosity of each color, giving as a result a similar system to how pixel color is controlled in any RGB display.

While creating a LED-based screen is possible and it's being done commercially, the size, power consumption and dot size make it only useful for large screens for sports or music events.

At a smaller scale this same technology seems cool for arts projects. The problem is that while many microcontrollers can do PWM, they have a limited number of outputs, and three of them are needed for each led.

Alternatively a matrix-like is possible for controlling arrays of RGB LEDs, but sacrificing its maximum luminosity.

Searching around the net several solutions pop up: serially addressable LEDs using one microcontroller for each LED, a serial-register-based RGB LED controller and an I2C-bus RGB LED controller.

Trouble on Googleland

2010-02-24T19:09:00.002+01:00

Just as Google seems to be facing some trouble with EU regulators, my (till now) trusty Gmail account started to give me trouble too.

I started a thread on Gmail help forums a week ago complaining of a sudden and weird problem. It turns out that many people are reporting a similar problem.

A cool feature of Gmail is that you can fetch emails from other accounts supporting POP3 access. It has been working great for a long time, with the added benefit of using Gmail's spam filtering on that other account's emails.

Unfortunately, starting two weeks ago, Gmail stops fetching emails from these other accounts for no good reason. While a fix has been posted: save the affected account settings again, this fix does not last long and problem eventually reappears.

While it might look like certain ISP is to blame, given the different and varied error reports it looks much more likely that trouble is in Gmail systems.

Wake on lan

2010-02-19T18:05:00.007+01:00

Recognizing the big amount of energy being wasted at my university, a system for waking up a computer has been set up. In the past many people, including myself, had no other choice but to leave the computer on if you might want access it remotely (as directed-broadcast is not allowed on campus' network, there was no way to send a Wake-On-Lan magic packet from outside of campus).

The new system put in place allows users to wake up their computer from the university intranet, which is a big plus. Alternative systems were available but only worked on certain subnets and you need to know you computer's MAC address (something I have to tell you I've never been able to memorize).

However, and there is always a catch, I realized my computer (an ASUS P5G33) did not seem to accept the wake-on-lan feature. I am quite doubtful about following the advice I read on a forum, even more if it requires reflashing my motherboard BIOS with a firmware many tools refuse to accept. However, I decided I'd risk my system this time to see if I can get WOL working.

In the process I learned that I need to boot up my system with MS-DOS. Not having an MS-DOS system boot floppy, nor a flopply drive in my system proved a problem. Luckily I could get the instructions to install FreeDOS on a USB pen drive. And because this install was bootable, I could finally got my system capable of running AFUDOS.EXE utility to re-flash my system.

Unfortunately some side effects showed up after the process was finished: now BIOS reports my CPU temperature is 4 degrees Celsius and Suspend has became non functional, as my system is non responsive after waking up from Suspend state.

But to make things worse I failed to see anything remotely similar to "Enable Wake On Lan" on the new firmware (though other people reported it solve their problem with WOL). And, of course, everything change I tried in the BIOS did not fix my problem.

Days later I read some advice on our computer center help info that turned my prevoius failure into a success:

sudo ethtool -s eth0 wol g

What this command does is to enable network card to be waiting for a magic packet to wake up the system. Apparently default startup configuration of my Ubuntu system does not enable the feature on the network card and so, the system looks dead (and not sleeping) to wake-on-lan.

In order to make this change permanent it is a good idea to include it somewhere in the adapter initialization process (i.e: if-up.d scripts).

Update: Once again, it happens you should not trust all what you read on the Internet. Out of curiosity, I reverted my motherboard to the original BIOS: Not only I've recovered flawless suspend operation and CPU temperature measurement but Wake On LAN works too. It turns out replacing BIOS was completely unnecessary, but I was fooled to believe the opposite due to both my failure to make WOL work and these reports I read on some forums.

What a disappointment

2010-02-04T22:17:00.004+01:00

As I mentioned a few days ago a talk by Richard Stallman was held on campus and I decided to go. The talk was along the lines of the four freedoms (kind of Stallman's version of Asimov's three laws of robotics). But almost at the end of the talk and before the questions he invited to another unannounced speaker who had some rants about the university.

Everyone is entitled to her own opinion but this was not the reason why I was there so I left. I cannot comment on that other speaker merits but it felt like a commercial in the middle of the talk (and keeping you there from leaving if you wanted to listen the question).

Should that individual have announce his speech people might have decided whether they wanted to attend or not, but the way it was done it felt like a trap. What it may be relevant here is that the university was providing a conference hall for free based on the idea Stallman's speech was of interest for our student and faculty.

As expectation was building up the event was moved to a larger hall, that was not free to have but our school assumed the cost based on the fact that one of our professors was named as the contact person on campus.

I felt someone was not playing nice here. Whether Richard Stallman was deceived or felt he had to step forward to defend someone's speech rights, I do not know.

Bottom line is that I left the conference hall with a bitter sensation. If Stallman's speech is all about ethics he should remember that action speaks louder than voice.

VMware did it again!

2010-01-28T12:15:00.003+01:00

I've upgraded my main desktop machine to Ubuntu 9.10 and one of things I need to get going is VMware's VM Player. I've been pleasantly surprised to discover that the new 3.0.0 version of wmplayer does include a new feature to create new virtual machines. While I had no complaint using easyVMX site I am extremely happy of having this new feature, previously only available on VMware Workstation product.

So, thanks a lot VMware.

University Talk

2010-01-27T13:30:00.002+01:00

Next week, Richard Stallman will give a talk at UPV campus (Conference Hall at building 1H) on Thursday February 4th, at 5:00pm.

Richard has already visited UPV before and can speak Spanish, so I guess that is what he'll use. His views about the software development and ethics are all but conventional. But now that the free sofware concepts have spread open wide many people share many of his points of view.

Not sure, however, if Richard still thinks the Copyright Levy (canon digital) we have in Spain now is fare.

Temperature logger needed

2010-01-16T12:04:00.005+01:00

Heating and air conditioning are the cause of much trouble on campus. Yesterday I was asked to make a decission as it was believed one of our buildings was too hot because of the sun. But, as I'd like to make my decissions based on facts I decided to setup a temperature logger. As heating is off on Sunday (but Sun is only off at night) I'll be able to compare the temperature profile of Sunday against all the other days when the heating is on.

Unfortunately no data logger was available so I set up my own one using three simple elements: An arduino board (actually it was an iDuino I had lying around) a Dallas Semiconductor (actually now part of Maxim IC) DS18B20 digital temperature sensor and a PC.

I adapted some code I borrowed from Nuelectronics to read the temperature and I transimted to the PC over the serial port. On the PC side (my office PC is running Windows) I had to program it using VisualStudio, so I created a simple VisualBasic program, whose only purpose is to add the time to the temperature received over the serial port. By redirecting the console output to a file I collect the measurements to a file. Alternatively you can use this code written in Windows PowerShell (remember to save it with .ps1 file extension).

I connected the DS18B20 using the two wires configuration, so an extra 4.7Kohm resistor was needed, but then only two wires are connected to the sensor (instead the three) as this was more convenient to get the sensor located on the right place.

Update: I've got some trouble with PowerShell as it outputs Unicode that some of my scripts are not happy with. In order to change the output I used the out-file cmdlet with -encoding UTF8 and -append parameters instead of the usual stdout redirection operator (>).

New year new toys

2010-01-13T12:15:00.003+01:00

During the last holidays I've been playing with a new Linux board that I've found quite interesting. It is an open project developed by a Spanish company which in turn enriched the Beagle Board idea with a lot of cool hardware: wifi, Ethernet, Bluetooh, RS-485, LCD controller, etc. They both share many other interesting peripherals as 3D accelerated graphics board featuring HDMI output, microSD memory socket, audio I/O and DSP,USB port, JTAG port etc.

The so called IGEPv2 (not sure it is a good name as I find it quite difficult to remember, maybe I'm aging) is a cool piece of hardware that comes with a Linux distribution name Poky and it based on an ARM Cortex-M8 processor running at 720Mhz that needs less than 3 watts for the whole system. It can run Ubuntu and many other ARM-based Linux distros. And it costs 140 Euros, which I reckon it is a sweet price.

Put it together with a large HD display and you have a point of information for the public. You may even hide the card inside the HDTV guts. And because it has both Ethernet and wifi it is going to be easy to be networked. Or you can add a hard drive to have a multimedia player box. Or just use networked storage for it.

Given the fact the processor has all the bells and whistles (memory management) it runs a normal version of Linux and not uCLinux. This basically means whatever you can develop on the Linux platform can run on it. Do you want an embedded server? Well, this can be a much better piece of hardware that SheevaPlug.

International version of Kindle DX

2010-01-07T22:05:00.003+01:00

It seems you can pre-order an International version of Kindle DX from Amazon. Same price as US version.

In another front there seems to be more players to the "larger" ebook format, the Skiff and the QUE showing off. But, while some demo new ideas, it seems Apple is about to surprise us (ok, maybe not) with a real device by the end of the month.

Happy New Year and other stuff

2009-12-31T10:30:00.004+01:00

This year has been an exciting one on the technology side but it is been a crappy year for most economies of the world. I keep my fingers crossed for a better 2010 on all fronts.

As you can see in the picture of the right, the Kindle DX has an annoying "feature" of showing the full media box of PDF files instead of the crop box. That means you have to recreate the PDF file if you want to get rid of these elements only useful for the print house. The problem they create is that some of the screen real state is wasted on them, making the rest of the page smaller.

My verdict about Kindle DX screen size is that it is too small for viewing A4 or US letter PDF documents comfortably but most PDF formatted books will be ok tough.

January issue of Circuit Cellar magazine will carry an article I authored. It is an Arduino-based project for a three axis stepper motor PC interface. Please note simultaneous use of several axis was not desired nor implemented. Popular stepper motor driving modes are explained and Arduino source code is provided. If you need simultaneous axis working at a time, you can check Reza's blog that contains a more professional approach.

From what I have read, it seems that Circuit Cellar magazine will join forces with Elektor magazine for a better worldwide coverage.

Hack-a-watch

2009-12-27T15:34:00.004+01:00

Latest development system for Texas Instruments "wireless" micro-controller comes in the form of a watch. Yes, a regular watch that can track several variables besides the time passing.

Besides the watch, the kit includes an USB RF interface and a USB emulator for software debugging. The watch itself includes a 3-axis accelerometer together with temperature, pressure and battery-level measurements.

At $49 it is a steal. No wonder they are out of stock. There is a wiki too.

Ultrasound ranging on Arduino

2009-12-17T20:14:00.004+01:00

I've recently bought a sonar circuit for distance and temperature measurements. Actually you need to know the temperature if you want to get an accurate distance measurement as it affects sound's propagation speed.

Less than $20 shipped, the URM37 unit is compact and full of interesting features: It has a dual interface as it can use RS-232 levels or TTL levels. Be careful because it defaults to RS-232 and these voltage levels can damage many 5V devices, including Arduino inputs.

It has several operating modes but I've used the serial interface. URM37 library comes with a modified software serial port library that allows you not to use any two available digital pins to interface with the sensor. This way arduino hardware serial port is free to be used for code uploading.

Another cool feature of the sensor is that it can control a RC servo so you can mount the sensor in a mobile platform to get the distance measurement at different angles.

Excellence in Teaching award

2009-12-15T16:31:00.006+01:00

I've been granted an Excellence in Teaching award from the local government. Among other things lecturing in English (or other foreign languages) and having high-marks on student surveys of teaching were topics assessed.

Now it is time to look around and thank all the people that made this possible: from my colleagues who share an interest on teaching to my students who keep on asking questions. From all of them I learn a lot every day.

I'm also grateful for my University and government that through various programs have supported different visits and stays at foreign universities.

And last, but not least, to my dear family and friends who have always been there for me.

For all of these I'm grateful.

Enable USB Networking on Kindle DX

2009-12-12T12:19:00.002+01:00

The first thing is why in hell you may want to do this? Or even what the hell is this usb networking thing?

The thing is that those who are outside of coverage of Whispernet wireless network cannot get some of the Kindle features to work. But even if you enable usb networking you are not getting back 100% of the functionality. Let me tell you some of the things I've learned:

Apparently Amazon will send you a client digital certificate to your Kindle through Whispernet (and only that way), so future orders from you Kindle can be properly authenticated as yours (so you cannot refuse payment I guess, among other things). That means that even if you get your Kindle to access the Internet (ie enabling USB networking) you won't be able to register it to your account (though no error message is presented to the user).

So what USB networking can serve for? Well, enabling USB networking allows you to connect to the Kindle as a network device and to access its Linux system for doing changes, checking what's inside and, if you are not careful enough, to brick it.

If you still are curious about playing this game let me tell you what you need to do:

Get a Kindle.
Get the binary from this thread.
Copy the proper .bin to the root folder of your Kindle.
Do a manual upgrade of Kindle firmware (you do this by pressing Menu/Preferences and the Menu again/Upgrade Firmware).
On the seach box of you Kindle type ;debugOn and `usbNetworking
Connect USB to your computer and you should get a new network interface (defaults to 192.168.2.1 and Kindle would be 192.168.2.2 device).
If you want Kindle to have Internet access you'll need to enable Internet connection sharing on your computing and to populate /etc/resolv.conf on Kindle with a valid DNS nameserver.
You can restore normal USB behavior on Kindle but restarting it (just make sure you delete /mnt/us/usbnet/AUTO file or you'll be running circles).

But at the end of the whole process the most useful thing I could achieve was to set the date on my Kindle DX. Browsing Amazon's Kindle bookshop is possible too but ... as you do not have a digital certificate you cannot download book samples nor you can get access to wikipedia. However, as you are connecting through your computer ... well, you can use your computer to do all these things faster and better than with you USB connected Kindle.

And, regarding my current experience with Kindle DX I would say that size matters and DX is lacking a couple of inches more. If I just could use one of the techniques I get on my mailbox to get a few more inches ...

Got Kindle!

2009-12-06T10:58:00.003+01:00

Though it's been one of the most difficult items to buy, I finally manage to get my Kindle DX. In a previous post I detailed the different failed attempts, but finally at the third one I've got my Kindle DX delivered.

Incidentally I discovered that my first buy from Amazon was stolen and being already used in USA. How did I learn that? Easier than you may think: When you buy a Kindle form Amazon (unless it is a gift for another person) it is registered automatically to you account. Next you can manage your Kindle from Amazon's website. One of the things you can do is to check the status of the documents that have been delivered through Whispernet and those that are still pending.

There is a default "Thank you letter" that is delivered to each customer. As Amazon sent me two Kindles (first shipment was lost, replacement shipment arrived) I had got two Kindles registered on my account. Each one had different email address and to my surprise I could see that that the "Thank you letter" had been delivered to my first unit (the one never arrived) on Nov 13th. This unit was shipped on Nov 10th but it was never received. The second Kindle (the one I received) had that same letter pending as I'm based in Spain now and Whispernet does not work here.

I notified this fact to Amazon and my first Kindle was removed from my account. I was warned that the did this to protect me: Those who stole it form the mail could buy books that would be charged to my account. I haven't thought about this but I'm glad Amazon did it for me.

My first experience about DX is that it is comfortable, the 5-way joystick works well but I wonder how durable it will be. A4-size PDF read well, though I expected DX to be slightly larger. Right now I'm upgrading it to the version 2.3 firmware.

Postgresql UTF-8 weirdness

2009-12-02T12:03:00.004+01:00

I was recently moving data from a Postgresql version 8.0 database to a 8.4 on a new server. The database dump was made on a UTF-8 system and it was moved to another system using the same encoding. However I was getting some errors when trying to recover the data. Several encoding errors where poping out. A closer inspection revealed that those were indeed a few encoding-rule violations. For some odd reason some data fields ended up with bad data, some double-byte characters had the first byte missing (it was 0xc2 in my case).

I solved the problem creating a small filter program to add the missing byte of these characters from the database dump. Not very nice but it worked. Why the problem developed in the first place I do not know.


#include <stdio.h>

main()  {
int a,c;
 while((c=getchar())!= EOF)
  {
  if(c>0xe0) continue;
  if(c>0xc0) { 
   a=getchar(); 
   if(a>0x7f) putchar(c); putchar(a); 
  } else if(c<=0x7f) putchar(c);              
 }  
return(0); 
}

Patience may be rewarded

2009-11-30T18:56:00.007+01:00

From Wikipedia: Patience is the state of endurance under difficult circumstances, which can mean persevering in the face of delay or provocation without becoming annoyed or upset; or exhibiting forbearance when under strain, especially when faced with longer-term difficulties.

When the delivery deadline was reached without getting my Kindle DX I was told to call Kindle Customer Support. Though I've insisted I was abroad I was given no other option that to get a refund.

Three calls later, and three extra waiting days, I was "rewarded" by a new shipment, this time One-Day Shipping at no extra cost from Amazon. I still do not want to start dancing till I get it home. However I hope this time delivery will happen (if not, I will find out quickly).

I am really happy I could use Skype to call Kindle Customer Support 800 line. If not it would have become an expensive enterprise as it took me more than half an hour at the phone to get this result. In fact, last Friday I was told a refund was my only choice, but thankfully today I've been offered a new delivery, fast shipping, no hassle. I would say this is the way of doing business right. Especially once first delivery has failed and I've been patiently waiting all these 22 days.

What it is particularly ironic is the fact that Skype is an eBay company (see two posts back).

Update: It arrived to my remailer address on time. Good job Amazon!. Now I'm sitting here waiting for my remailer to contact me so it can be forwarded.

Update2: Remailer worked as expected and my Kindle is flying home. I hope I'll receive it tomorrow Thu, Dec 3th. It was surprising there was such a thin difference (10%) on Fedex and USPS rates.

How not to get a Kindle DX

2009-11-24T09:32:00.004+01:00

Apparently I'm out of luck. Last Nov 8th I ordered a Kindle DX from one Amazon's associate. It was shipped Nov 10th and that's all I know since. As the estimated delivery date passed a few days ago I contacted customer service and I was asked to wait a few more days and then to claim for a refund.

As this is my second unsuccessful attempt of buying a Kindle DX, though I have not yet got the refund of my first attempt (still sitting there on my PayPal account) I reckon there is not going to be a third attempt. Whether there is some black magic involved or not I do not know. When I tasked myself with buying a Kindle DX I was not aware it would be so difficult.

Last time I could blame eBay seller, but this time I was buying from an Amazon associate (Warehouse Deals). I'm not buying a DR1000S as battery issues render it almost useless. Something that for a device costing double than a Kindle DX I cannot accept. So maybe I'll wait to see what Plastic Logic delivers in January 2010.

Fighting with shady eBay sellers

2009-11-10T22:05:00.005+01:00

I'm disappointed Amazon is not yet offering an International version of Kindle DX. I'm disappointed Plastic Logic is not delivering a product, just the name (QUE) is not enough to me. So I decided to get a U.S. Kindle DX and, as Amazon is not selling it overseas I thought eBay was a good place to get one.

After a few days I saw that, from time to time, some sellers offered refurbished units. I read good comments on Mobileread.com and Lectoreselectronicos.com about refurbished units (i.e. look brand new, 18% off) for $399 so I was sold.

I bought one DX from a seller named iRebates after contacting with a previous buyer who have had a good experience and was based in Spain too. That seller had a good reputation with more than three thousand successful transactions. It all looked ok. So I shelled out the dough and sat down and waited. And then waited a bit more and essentially nothing else happened. Three days later I asked the seller about my shipment. I was told it had not happened yet.

After more than one week without news from the seller I emailed him. Nothing happened. So a few days later I emailed again. Same result.

By that time seller still had listed items on eBay and feedback was coming in. However the amount of negative feedback started to show a steep increment. Things were looking really bad and still no news from the seller. Time to file a PayPal dispute.

When you file a PayPal dispute, PayPal contacts the seller/buyer to set the record straight. Later, if you're unhappy you can escalate the dispute to a claim. This time however, I was only allowed to file a claim (I guess something was already going on regarding this particular seller and PayPal).

Next day I've got a message from PayPal stating my money was refunded. Good, at least I'm not burned. However, I was left unharmed but without my Kindle. By then, iRebates had no more products listed for sale on eBay.

Things can always get worse, so next day I received an automated message from eBay stating that the seller had filed an Unpaid item case against me (actually it seems he did this with many customers). Two eBay customer representatives later I learned they could do nothing to help me at the moment. Though I was told to respond I never found out what I could do to respond. I think it is a loophole in eBay system what allows a seller who received payment to file such a claim.

Maybe the seller was trying to frighten customers with an eventual Unpaid item strike if they left negative feedback. However negative feedback was the only possible outcome of this shopping experience.

So I thought it was time to disturb some of my friends in the states asking them to forward a package from Amazon to Spain. But what if there is any problem.

Eventually I settled with a company doing the forwarding work. I reviewed both MyUS.com and Shipito.com and I used the latter. Now I now Amazon's partner seller has already shipped my DX to my address in California. Hopefully I 'll get it home in a few more days.

27" iMac itch

2009-11-09T21:02:00.010+01:00

It's been reported that many geeks are developing a kind of itch associated with visits to the Apple store. Unfortunately I went to a local dealer last week and I've catch it. The only cure I've found is to just go and buy a new 27" iMac.

While the display is awesome (I've got 17" before), I'm quite impressed with the new mouse. I really like it. If mouse battery usage is ok or not I can't tell yet.

Display works great even angled. Sound is ok. Desktop is tidier now. Only doubt is USB access, as being in the back I have a difficult access to it (but I might be moving to SD format instead for easier access to the slot).

I just hope I won't be reporting soon any trouble the system is giving me (as it has happened to me in the past).

Please remember I've warned you: Do not get close to an Apple shop!

Update: I have had this problem with my MBP before and it is one annoying error when using the shell in Snow Leopard. Every type your write a pipe, you have to leave the next command with no space from pipe bar. If you leave a space the shells cannot find the command. I was copying some files from another system using nc 1.2.3.4 1234 | tar xv - and I was getting an error as if tar command was not found. Of course tar command was installed and well.

Update2: Actually I was wrong: The error happened again when I was having a remote shell session with a Linux host. Then I realized the problem was not the shell command interpreter on Snow Leopard but something else. A bit of trial and error led me to the root cause of my problem. I had to press "Alt" to get the pipe sign. If I am not releasing the "Alt" key fast enough, it is still pressed when I type the space bar. This leads to a blank space on Snow Leopard terminal but apparently it is not a real space character but another one, so the host shell thinks this is part of the name of the next command and it fails to find it. The solution is simple: be careful not to press Alt while typing a space.

Just for the sake of curiosity I did this(second space is Alt-space):

$ echo " " | hexdump -C

00000000 20 c2 a0 0a | ...|

Yeah, 0xc2 0xa0 is not definitely a 0x20 space. Is it? Actually 0xc2a0 is a NBSP in UTF-8!!!

Merging PDF files

2009-10-28T09:24:00.004+01:00

I do love Inkscape program. However, there is one thing it is still missing (it's not the program's fault though), the ability to handle more than one page documents. I recently was producing some drawings at work and I wanted to make a single document package with all the drawings to be emailed to my colleagues.

As I can produce PDF output from Inkscape, I searched for easy ways to merge several PDF files. I do know Adobe's Acrobat can do that, but I was looking for a cheaper alternative. I learned that you can use command-line ghostscript to get this done (provided you have it installed) easily.

gs -sPAPERSIZE=a4 -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=outfile.pdf inputfile1.pdf ... inputfileN.pdf

I learned too that it can be done online, in fact there are several sites (mergepdf, joinpdf) you can use.

Though there are certain limitations (encrypted PDF files are a no go), it seems I no longer have to worry about creating multipage PDF easily (of course it will be even easier when Inkscape includes multi-page support).

From VMware Server to ESXi

2009-10-21T22:45:00.004+02:00

One of the cool features about some VMware products is that they are free. Both VMware Server and ESXi are free virtualization platforms. The main difference is that while VMware server is running on top of your computer operating system, ESXi is a thin software layer running over your hardware. That saves important resources that can be better used by the virtual machines you want to run on top. ESXi only uses 32MB of RAM. You can watch this presentation about ESXi. The main problem I've got at the moment to get ESXi tested is that I need to buy a SATA disk as PATA is not supported.

Kindle outside of U.S.

2009-10-09T15:26:00.003+02:00

I've just read today on Amazon.com website a Jeff Bezos letter announcing the availability of Kindle for customers outside U.S. Of course this also means that wireless access is going to work in your country.

I'd be buying one now if DX was available. Unfortunately only 6" Kindle is offered at the moment. However I guess they will be adding DX soon.

Update: There are a few things that do not add up well. Kindles are only sold from U.S. at the moment. That means you have to pay customs, plus overseas shipping plus an slightly more expensive version of Kindle.

Another source of trouble is that Wireless acccess to Wikipedia from Kindle International has "experimental" status, whatever that means. It is not so with US Kindle. And to me, wireless free access to Wikipedia is well worth a price premium. But ... if Wikipedia access is dropped then I do not see enough value on the wireless delivery of paid content.

H-index

2009-10-04T19:59:00.003+02:00

There are many ways to measure the "output" of a researcher. It is likely there are many ways to measure it because none of them is right for all the cases. While many consider citations of a paper as some type of endorsement of other person's work, there many ways to turn that into numbers.

And we want numbers so we can compare performance easily. I was asked the other day to provide my H-index. Problem was I have never heard about it before (only my fault). Just a wikipedia query later it turned out the idea was quite simple. H-index was proposed by Jorge E. Hirsch from UCSD and it is sometimes called Hirsch index or Hirsch number too.

This is how it is obtained: Take your publications list and sort it by the number of citations. Now start counting papers from the top (most cited paper) and continue down till the number of citations is lower than the count of papers. The current count (or one less) is your H-index.

So an H-index of, let's say, ten means that person has published at least ten papers with ten citations (or more) each.

The main problem with this index is that citations are not always counted the same. For example, Google Scholar use to report more citations than Scopus or Web of Science. Number of authors is ignored by H-index, and it somehow limits the maximum H-index to the number of your current publications, no matter how groundbreaking they are.

VirtualBox on Snow Leopard

2009-09-29T09:46:00.002+02:00

I've heard some news about troubles with VirtualBox when running on Snow Leopard. It was too late for me as I've just upgraded a couple of my systems. So I installed VirtualBox and I created a sample Ubuntu 9.04 system from scratch. Everything ran smoothly. Network and USB access worked as expected too. I have no idea if there is trouble running a VM you created before upgrading to Snow as I have none.

I used to be a fan of VMware's free VMplayer. Unfortunately there seems there is not a free version OS X. VirtualBox appears to do a nice job too. There is a quirk though, USB devices need to be registered to be used by the VM before you turn it on.

Dude, where is my C.a.R. ?

2009-09-20T20:21:00.004+02:00

While reviewing some of the answers to one of the questions of Code Jam Round 1C, I've learned about this cool software. It can be run using Java Web Start, so you don't even need to install it. What is it about? I reckon it will make some Math teachers very very happy. In short, it is a drawing tool for geometry-oriented drawings. It can export to SVG or EPS too. Mastering on the use of the program may take a while, but I see lots of potential on this tool.

Could not make it to the second round

2009-09-16T19:19:00.006+02:00

I've failed to make it to round 2 of Code Jam 2009 last weekend.

I failed on getting the first problem (All your bases) right and that ate most of my available time. I was able to get the third one (Bribe the prisoners) right (bruteforcing it, not very elegant).

So I used some time to get the first problem right after the contest :-)

By the way, I later learned that there was a hidden constraint, as output value could not be larger than 10^18. That meant that maximum base could be 16 (as 1023456789abcdefg is base-17 is larger than that, 49030176097150555672 in case you're wondering).

Here you have a simple solution in Java. And, yes, you can use Long.toString(String,int) instead of BigInteger, though the latter will cover a wider range than the problem statement requirements.

X11 on Snow Leopard

2009-09-11T08:25:00.004+02:00

A few days ago I've got a shiny new MacBook Pro. Instead of coming with Snow Leopard installed, I've got a rebate on the price for the cost of the update to SL. I've installed Snow Leopard now but the disc does not contain a version of X11. As GIMP and Inkscape software depend on that I'm searching for the right version to install. I could use some help if you already know where to pull it from.

Update: I'm happily running the GIMP on Snow Leopard. Contrary to my claim above, X11 is included on Snow Leopard, you'll find it in the Applications part of the optional install package.

SSH into my e-book reader?

2009-09-09T18:25:00.023+02:00

Yep, it does sound odd, so a bit of an explanation may be welcome: I've bought me an electronic book reader a while ago (a Papyre 6.1 from Grammata). It is the same device as the Hanlin v3, Bebook, LBook and many other brand names given by sellers on different countries.

The reading experience has been quite good. Actually it's been better than I expected. However, every now and then, like Windows 98, the system would refuse to turn page and freeze. After a few seconds [I suspect] the built-in watchdog timer quicks in and reboots the system. Total time is less than 30 seconds but the worst part is that you've lost the book page you were in.

After checking several forums where many users complain about the same thing but no real solution was offered, I learned that an "alternative" firmware was available for a wide range of devices, including mine. Even better, there was a live version you could try before flashing it on your device. Who could ask for more?

This firmware, known as OpenInkPot, is lacking of any kind of DRM support (which I do not need). And it also lacks of USB storage device emulation. That means that when I plug the USB port into my ebook it does not pop up to my system as a storage device (something the original firmware did) so I can add new files to system. This is not a big problem as I can easily take the SD memory out of the unit and plug it into my computer to add more books to my collection.

However, out of curiosity, I learned that I can use USB network shim so I can SSH my ebook system.

#as root user
ifconfig usb0 192.168.111.2 netmask 255.255.255.0

#later you can transfer by:
scp book root@192.168.111.1:/mnt/storage/

#or if you want to send it to the SD card
scp book root@192.168.111.1:/media/sd/

is the magic needed to be able to later connect to the device using Ubuntu.

Now I can use SCP to transfer files back and forth. But I'll have to wait for a few reading sessions to tell you whether the glitches have gone with this firmware or not. The picture on the right shows the looks of the new file selection menu.

There is a long list of supported devices, so if want to give OpenInkPot a go it can be fun. (But don't blame me if you brick your system!).

Code Jam 2009

2009-09-04T12:06:00.005+02:00

I've just passed the qualification round of Code Jam with the feeling that I'm getting dumber every year. I only passed the first problem (Alien) and I've got stuck on the second problem (Water Basins). Third one (Welcome string) looked like the Speed Limit problem on 2008, but I did not attempt to do it.

A plausible excuse is that I did not have the time ... Yes, I like that: I was busy working so I did not have time to waste playing this Code Jam thing.

BTW, It was me the guy who asked about the error message on the Q&A. The error message said my solution file did not start with the string "Case #1:" but that was not true. The correct error message should have been that my solution file did not start with the string "Case #1: ". The difference being the space after the colon.

Update: Here you have the three problems solved in Java.

Gmail down

2009-09-01T22:23:00.004+02:00

A the moment of writing this, Gmail is giving the usual Server Error message you get when things go wrong. I hope the problem will be fixed soon. I've learned that Twiter can be useful whenever this happens. You can check by yourself with this query.

There is also a reporting tool from Google that can come in handy.

Gmail's new feature

2009-08-04T19:16:00.004+02:00

As a Gmail user I've sometimes trouble with certain email alias unhappy of me sending from an SMTP server outside of our campus network. Another source of weirdness is the fact that while the From: field shows what I want, there is also a, sometimes not hidden, "On behalf of" that is broadcasting my gmail account even when I'm not interested on doing so.

It's great that Gmail has added a new feature that allows Gmail servers to use your organization SMTP server as the outgoing SMTP server for your corporate email address.

The two above mentioned problems are fixed then: You can send to email alias only intended for local users just right from Gmail (no nasty Outlook anymore, thanks). And secondly, there is only now the right From: mailbox.

Cool!

Technological jumps

2009-07-30T10:35:00.004+02:00

From time to time we witness significant changes on how things are done. In terms of how we listen to music in the last ten years I've seen several interesting changes.

Ten years ago I bought my wife her first MP3 player: It was Diamond Multimedia with 32 MB (yes, Megabytes) that could hold a couple CDs of 128kbps MP3 music. Since then on I've bought many other MP3 devices for my household. However, that marked the end of traditional media (CD-audio) for our portable uses.

While MP3 players have been around for quite a while, it seems that Apple's iPod is now the king. And while kingdoms do not last long in this market I guess Apple has done something right.

Many people (like myself) are device-centric. For quite a while I favored Creative players and while I've never bought music from iTunes, I've bought some software there. Meanwhile I've stopped buying from Creative after problems with several players.

And now that I have time I've played a bit with another thing that could change the way we listen to music at the computer. In the same line as Napster and Audiogalaxy helped people to download music from each other and later where shutdown for copyright infringement. Spotify presents us a compelling service that delivers music to us from a huge selection, I mean huge, over the Internet. Their service is not about downloading files but streaming on-demand music to your computer.

Spotify had a catch that prevented me to use it more: It only worked on Windows and OSX. However, it works over wine too. So that means Linux users can happily use the windows binary.

I know this is old news for many, but till now I did not have the time to learn more about Spotify. Whether you use the free service (that contains some ads) or the fee-based one (ad-free) the system is easy with a clean interface. It just works.

Apparently, Spotify is not available in USA. I'm sure the agreements for not being sued haven't been signed yet. I guess Spotify business is going to be based on the fees collected from subscribers and commercials (both on the UI and the audio of free service). So I really would like them to succeed as they seem to be offering yet a new way of doing a business that till now proved quite elusive: Recording Industry seemed to oppose to any change to the status quo. However, while doing that they are putting every time more and more on the edge of extinction.

Give Spotify a try and listen to some old or new music.

There seems to be an iPhone version coming soon.

Visit Norway

2009-07-19T16:43:00.004+02:00

It's been hectic times around here, mostly due to different changes at my workplace. Now it's time to start thinking on having some vacation. A summer trip seems a good idea but this year I've selected Norway: beautiful but expensive.

While there are tons of information on-line, I have found details are a bit sketchy. This is likely due to the fact I'm interested on cheap accommodation. Maybe the average wages in Norway are much higher than in my home country, Spain.

I've got some trouble getting things done online. There seems to be some odd behavior and this booking website, when browsed with Firefox on Ubuntu 8.04. The worst thing is that it was this the browser I was using when booking my flight with Norwegian.com and I was offered a very competitive car-rental price at the end of the airplane booking process.

Unfortunately when trying to go to book the car I was offered an almost empty page. I was wrong when I thought I could go back to the former page too. So I realized there was not way for to either book the car here nor to download the details about my flights.

To make things worse I had refused to create a user on Norwegian website as I wsa not planning to be buying more tickets anytime soon. However, lacking of a user login I had not clue on how to get my flight details. Email was producing no document either. I was expecting a bit more help after shelling out a couple of grands.

My wife, using her iMac, reported that airline website might allow us to get our flight details using the flight locator and lastname. Unfortunately, that didn't work either. No clue about why.

Frustrated I decided to go to check my flight on Amadeus system. I used CheckMyTrip website. I used the flight locator and my lastname (that included a dash) and voilà, I finally obtained my flight details. Good news.

Then I realized that the dashes on our lastnames have been erased in the booking process (maybe their online system does not like dashes). So armed with this new info I went back to Norwegian website and, finally, I was able to recover all the documents about all flight (pdf files with barcodes that can help you avoid the check-in if you fly without baggage). Of course the trick was not to used my lastname dash!

Even better, I was now able to book the car-rental at that best rate but only if I was using my wife's iMac with Firefox.

I guess the moral of the story is to be very careful when booking on-line using not the latest version of browsers, and, if possible, use the nasty Internet Explorer on Windows that seems to be what many developers consider the "standard".

iPhoto Books: be warned!

2009-06-23T09:49:00.004+02:00

No, I'm not going to complain about the output quality (at least not yet as I'm still waiting for my order).

What I want to complain about is the fact that your iPhoto Book orders do not show up on your Apple Store account. And apparently this oddity has been happening for quite a while.

That means that there is no way for you to know about your order status. Of course there is a confirmation email sent to your Apple ID email but, what if your .mac account has expired? (then you no longer have access to that email).

To make things worse, once 1-click order has been activated iPhoto will not ask you for an additional confirmation when issuing a new order (I guess that's the 1-click beauty once your Apple ID email account works nicely).

Calling customer service did not help much, as I was assured my credit card was not billed and somehow I had no pending orders. Calling my bank gave me another version: My credit card was billed (and apparently my order was taking longer than expected to arrive).

At this point I was no longer sure the "easy" route that iPhoto promised to get my photo book was actually easy. Even worse, once I realize customer service gave me the wrong information after forcing me to wait several minutes at the phone I was angry.

To make things worse, I had order a second photo book by mistake (thinking the customer service information was right and being unable so see the order on the Apple Store site). And I could not find a way to cancel that duplicated order.

Thankfully, the link provided above included a cool tip. You can visit this url to know your iPhoto Book orders and, if within 90 minutes from your order, you can cancel it. What this information is not clearly stated on Apple Store I do not know. However I have asked them to fix this as it's been this way for at least two years.

Apple Store's answer:

iPhoto is an Online service that does not belong to our Store.

For any query or issue with iPhotos, please, go to http://www.apple.com/es/support/photoservices/contact_us/ . You will find a rebate to fill out, and in the next 48 business hours, an agent will provide you full support by email.

E-ink experience

2009-06-20T19:00:00.006+02:00

Not yet very affordable, but better than I expected. This is my opinion after buying an ebook reader. Mine is branded Papyre 6.1 but it's named Hanlin v3 in other countries. It's manufactured in China (what a surprise!) and it runs Linux (it has an ARM processor).

Definitely worth watching at. However I have not used it for more than a few minutes so I do not have an opinion about the long term usefulness of the device. But if it delivers what I've seen in the tests it is more than worth it.

Now I'm sorry but I'm back to reading, please do not disturb.

Update:

The reading experience has been better than expected. And the availability of contents has also been better than expected.

What I have not find, however, is a shop with the latest books. But that only meant some books cannot be bought but they might be available somewhere ...

For example, I was reading a paper copy of this book in Spanish. And I had no trouble finding an electronic version.

There is a cheaper electronic book in Spain called iLiber, but it does not come with a cover, earbuds or MP3 support.

Online network doctor

2009-06-10T00:57:00.002+02:00

Years ago, in a distant galaxy, I was a member of ICSI. Now I've been surprised about one their offerings to the community: A network analyzer. It's Java-based so it won't work unless you have Java support in your browser and you're happy running digitally signed code.
You may learn a couple of things about your network connection.

Yann Arthus-Bertrand's HOME

2009-06-08T13:08:00.005+02:00

A succession of breathtaking sequences shot from the air is the newest release by this widely awarded photographer. It's really worth watching.

You can get the movie for free! Movie is available in theaters all over the world (but apparently not in USA) and also in YouTube in HD. Although the beauty of the images might be better enjoyed on the big screen, you can have a look at it on-line.

What amazes me is that it is the creators of the movie who decided to release it on YouTube at the same time than in theaters. The release details were given on a press conference.

The movie has been sponsored by PPR, a French multinational in the fashion business.

Two useful additions to your Iomega Screenplay pro HD

2009-06-01T19:50:00.003+02:00

I've found the network transfers to take forever on this device. Between 1 and 2 Mbytes/second is really slow by todays standards. It means around 4GB per hour.

I'm happy with the torrent download functionality I mentioned on a previous entry but there is a catch: What if your download contains a sequence of RAR files? Yep, it happened to me with a 16GB download. Moving this back and forth to a PC would took more than 8 hours!!

So the obvious idea is ... why not to have unrar command on the SPP? And this is what I did. I looked for the source code, and using a buildroot ext2 image file I compiled unrar command. Now I can telnet to my box and launch it without the need of moving files back and forth. It's not lightspeed but it's minutes instead of hours.

The other improvement was to add SSH functionality by borrowing dropbear binary from OpenWRT project. Please have a look at dropbear documentation so you can install in properly on your system (a few files and links need to be created to get it working). It also includes SCP file transfers.

Trouble is not only on the digital side

2009-05-11T22:33:00.004+02:00

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.

Digital pollen allergy

2009-05-09T21:31:00.003+02:00

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 do if you have the proper tool for the job. And no, you cannot use a common brushed air blower you use for your lenses. Sensor surface (or filter) needs to be extremely clean to render clean photos.

I'm still in the process of trying one (or more) of the above methods to get rid of my sensor dust. For the moment I think my camera just has Spring fever :-)