somewhere to talk about random ideas and projects like everyone else



Raspberry Pi 14 August 2012

As part of the shift between long multi-kiloword blog posts which are somewhat more like press releases back into a sort of more personal (i.e. blog-esque) format, I guess I’ll talk about my newly-arrived Raspberry Pi. Right now, there isn’t terribly much to talk about since I’ve only had it for about two weeks.

I’ve been planning on getting a Raspberry Pi for a pretty long time, and I was actually pretty excited about that. For the weeks preceding the official announcement, I built a tiny script which ran in a ten-minutely cron job which would basically download the purported Raspberry Pi store (, note the dot-com rather than dot-org, which their homepage is situated at) and compare the hash, notifying me via Ubuntu’s built in notification system.

On that sleepless night when the actual pre-sale announcement was being made, I was incessantly checking, which had suddenly morphed into a server maintenance message (which remains to this very day). The anticipation was intense, and some twenty minutes after it was supposed to happen was when I realized that the whole time I had been checking the wrong page. The announcement came instead on, their main blog, and by that time, it was certain that all the distributor’s sites were already collapsing under the crushing load of a million souls crying out for a taste of berry-scented silicon pastry.

On the next day, I checked the sites again, and all the order pages were already closed. Either way, it wasn’t terribly useful for me because most of them didn’t support Paypal. Fast forward a veritable eternity, on June 16th, I was notified via email that RS Components that I would be allowed to order the device some time in the near future. Sure enough, on the 22nd, another email gave me a link to the order form, which I promptly filled out and I began the process of waiting. Not really, since I had other stuff to do and most of my interest had already vaporized at the daunting 7 weeks it was supposed to take.

Another eternity later, it arrived in some rather nice packaging. It actually came as a bit of a surprise, because I had become so accustomed to waiting that I had never really expected it to materialize so suddenly. But when it did, it was everything I imagined and more. It came in this rather nice cardboard box, which I eventually cut in half with an X-Acto knife (which nowadays, I use for all my paper splicing needs) to build a makeshift case. I fumbled around in a closet and found a neglected 16GB SD card (probably back from the era when point-and-shoots were actually preferable to mobile phones) and installed that weird Debian distro (after having a little internal debate on what to install). But the first thing I had done was plugged it into a monitor through a HDMI-to-DVI converter. I took the charger from my Galaxy Nexus (I wasn’t using it for anything since I charge it in my room from my HP Touchpad Charger, and my Touchpad idly draining power from a cool inductive stand, the standardization of chargers is really pretty awesome), and used that as my Pi’s permanent power supply.

I also had a 2000mAh LiPo battery which I was going to use with my Arduino LilyPad for some cool foot-operated telegraph which I wanted to use as essentially a UPS for the Pi, but a bit of googling reveals that that might possibly entail actual electronicswork, so maybe that’s something for later.

I turned it on, and lo and behold it didn’t work. I actually never quite figured out why. Then, I tried plugging it into a really old 13 megaton CRT TV, which makes me realize how it’s sort of weird that the unit of megatons is hardly ever used for things other than atomic weapons, and now it feels oddly inappropriate for a hyperbole for the mass of a TV, but maybe it’s actually sort of appropriate because CRTs are terrifying. So analog seemed to work, except for this problem where my keyboard would keep repeating letters and not working well. That wasn’t a good start.

But after a little googling from my Chromebook, it turns out the keyboard issues came from the fact that I had plugged in my only spare USB keyboard which happened to be a Logitech Mouse+Keyboard+Speaker thing and my teensy Galaxy Nexus charger couldn’t eke out enough watts to power it. And the issue with the HDMI-to-DVI thing was just because I needed to restart with the cable plugged in. But neither of them posed a real material issue because I had been intending to use it as a headless rig from the start.

The first thing I really noticed was how surprisingly easy it was to install things. I had expected the ARM repositories to basically lack everything which might be useful, but it turns out that actually almost everything I wanted was available. I didn’t dare compiling anything, but Node (albeit a somewhat old version) was available from the repos, so I never really needed to. I had to manually update to a new version of npm, but that wasn’t that bad. I set up forever to run a few apps, but not much.

One of the main reasons I could justify getting the Raspberry Pi however, was to run my Facebook logging script on something other than my main computer, and aside from getting confused trying to use sendxmpp, it was fairly straightforward.

Chrome Multitask Mode for Real with Multi-Pointer Xorg 04 April 2012

Google’s multitask mode was only an April Fool’s joke, but inordinately amused among us (read: me) might even venture into attempting such an irrational feat. While watching the video, it evoked some memories of something which I had stumbled across a few years ago, called Multi-Pointer X. The rationale for creating that wasn’t nearly as insane as the Chrome Multitask video made it out to appear, instead I think it was just the framework to support multitouch and other sorts of alluring interactions on the Linux platform.

So I decided to look into that again and within a few minutes of Googling, it appears that Multi-Pointer X has now been incorporated into the mainline as part of XInput2. So what exactly does it take to conjure and insult the multitasking gods?

The first step is quite logically to plug in another mouse. I happen to have three mice plugged into my computer anyway (there’s a perfectly logical rationale for how this came to be, my keyboard is some wireless Microsoft keyboard+mouse set but I really hate the scrollbar on the Microsoft mouse, so I instead used another mouse for the longest time until it started failing and sheer lethargy prevailed over disconnecting that obsoleted peripheral) but regrettably, I don’t have an additional prehensile appendage to operate the third mouse.

Right now I’m using a pretty much unmodified version of the latest version of Ubuntu 11.10. I just opened up a terminal window and typed in “xinput list

antimatter15@antimatter15-desktop:~/online$ xinput list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ A4Tech PS/2+USB Mouse id=8 [slave pointer (2)]
⎜ ↳ Microsft Microsoft Wireless Optical Desktop® 2.20 id=11 [slave pointer (2)]
⎜ ↳ USB Laser Wheel Mouse id=9 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
↳ Power Button id=6 [slave keyboard (3)]
↳ Power Button id=7 [slave keyboard (3)]
↳ Microsft Microsoft Wireless Optical Desktop® 2.20 id=10 [slave keyboard (3)]

Use the command “xinput create-master Auxiliary“ in order to create a new input device, and try running “xinput list“ again to confirm that the command has done your bidding.

antimatter15@antimatter15-desktop:~/online$ xinput create-master Auxiliary

Now it’s time for the third (or is it fourth) and final step, to reattach one of those master pointers into the auxiliary pointer. To do that, pick out some mouse. For me, I picked my “A4Tech PS/2+USB Mouse“ which is was my mouse with a broken scroll wheel. You can see that it’s been given ID=8, so that’s the number I’ll be using for the next step.

antimatter15@antimatter15-desktop:~/online$ xinput reattach 8 "Auxiliary pointer"

And then I can now use two mice at the same time for whatever ungodly purpose I desire.

It’s hard to take screenshots since it appears that every screenshotting or screencasting app which I can find seems to make the wholly unwarranted assumption that a desktop computer only has one cursor, but it does actually work. Though I don’t think I’ll ever be able to multitask through this scheme, it’s mentally jarring in far too many ways.

ShinyTouch/JS 28 August 2009

Yay for yet another demo that strives to mix an mash almost everything HTML5 related! ShinyTouch in JS dumps the stuff from a <video> tag with ogg encoded video (well, almost all video from linux is ogg encoded so it’s just whatever format i got first from cheese). It gets dumped into <canvas> and getImageData does it’s magic.

Interestingly, if you don’t use the video and just do data from a raw image, you get upwards of 125fps on V8. Adding the video, it ceases to work on Chromium (maybe a linux thing? this tells me it’s just linux, but you can never be so sure).

//At this point, run away as the algorithm gets messy and hackish

So the thing just searches from right to left up to down within the quad. When it finds a column of something that fits the rgb range of the finger that is larger than a certain threshold, it checks for a reflection from the point. If it detects a reflection then yay! it throws the data at the perspective warper (based on a python one which is based on a C# one and though it would probably be easier to port from C# to JS making long chains of derivative work is fun). If there wasnt a reflection then it logs that and if that number is larger than some othe rthreshold then it kills the scanning and goes on with it’s life. The reflection algorithm just takes the point 5 pixels to the right and assumes that would be a reflection if there was one and a point 15px above and 5px to the left (nasty stuff) and takes the hue value from their RGB values. It takes the absolute value of the difference of the hue values multiplied by 100 (or 200 in the python version) and compares it with a preset configuration variable.

So now that that horrible algorithm which was just whatever came to my little totally untrained mind first. But it works semi-decently, at least for me. But you can hopefully see how nasty it’s inner workings are and it inspires people to clean it up. It’s quite a bit more readable than the Python version and only 200 lines of JS so it won’t be too hard to understand.

But since HTML5 has no Video capture thing for webcams, and my webcam doesn’t work with flash so I can’t use that canvas<-flash webcam bridge i built, uh, almost 2 years ago. So now you just get to gaze at my finger moving for like 20 seconds!

Python Ports! 12 April 2009

I’m porting the multitouch concept to python. Why? Because i’m on linux now, mono sucks, and PIL is pretty awesome.

I’ve set up a mock-rig where there are 2 mirrors on the side angled by erasers with a crappy Creative NX webcam mounted on a textbook over it. It seems like the only practical use of this is for a multitouch-table sort because gravity makes it otherwise pretty hard to calibrate.

So after I rewrite the software I need to try getting it to parse an actual image. Then I need to somehow hook it up to streaming webcam data, and somehow do something else.

I'm A Linux Idiot 04 January 2009

So I needed to install phpMyAdmin, and having those epiphanies on how simple it is to install crap on Debian/Ubuntu, I typed in sudo apt-get install phpmyadmin and it worked fine. Mapped out all the dependencies, installed them all, and then popped up a nice user-friendly config window where you select which server to install it in.

I had Apache2, so i just hit enter. Opened up my browser and went to /phpmyadmin. hmm. 404? tried /phpMyAdmin, and same.

So I googled it, and there were all these success stories. I went and tried sudo dpkg-reconfigure phpmyadmin, that same window popped up, this time i tabbed over to the ok button. and pressed enter. Checked again, still broken?

So i found this guide, and it turns out you have to press space to select it -_-

Export to Silverlight 20 July 2008

You can export your animations to silverlight, almost flawlessly (though i’m on a linux box so I never tested them, they’re hopefully close to the Silverlight 1.0 specs).

The only problem, is that I have no idea how to put an animation in silverlight. Right now, it’ll squish every frame’s data together. into a merged display of every frame.