somewhere to talk about random ideas and projects like everyone else



Handwriting Recognition with Microcontrollers 30 June 2015

For my final project in 6.115, a microcomputer electronics class which I (and apparently nobody else) affectionately refer to as “leeblab”, I built a simple gestural input system. At its core lies an ordinary 8x8 LED matrix hacked into a low-res CCD and display coupled with a gutted expo dry erase marker used as a light pen. And per class requirements, it used a rube goldbergian cascade of TTL logic, an 8051, Cypress PSoC 5, an Arduino Pro Mini to process and massage the signals into USB HID compliant form, so that a computer might be able to use the contraption as a keyboard.

I had an 8x8 LED matrix laying around, and ‘twas the season that I had to come up with a final project for 6.115, a microcomputer electronics lab class. I vaguely recalled that an individual LED would generate a potential difference if you pummel it with enough photons. So I figured a cool and somewhat clever thing to do would be to create a display which could simultaneously act as a camera (pretty orweillian in retrospect).

I'm not totally sure about this, but I think this was the pinout of the LED matrix that I had. Notice that there doesn't seem to be any sensible mapping between spatial position and the corresponding pins

The LED matrix was something like this one. It’s wired using a technique called charlieplexing, where there’s a long wire along each row that connects the anodes of the LEDs, and another long weire along each column which connects the cathodes (modulo dyslexia).

You can imagine taking a battery and a few clips and touching one point along the row wires and another point on the column wires and see a single pixel light up at the intersection of those columns and rows.

Automatically Scanning on Lid Close with Arduino 30 May 2013

Arduino Scanner

Before the 29th of January, I had a rather irritatingly Rube Goldberigan scheme for using my CanoScan LiDE 80. It didn’t have native Linux support, so the only way I could scan documents was through a Windows XP (Technically MicroXP) installation inside a VMWare virtual machine extant for the sole purpose of indulging my blue moon scanning requirements. But after that fateful day, I had a new scanner which- in its matte black glory could reasonably produce bitmap reproductions from pieces of paper on its surface, notably sans the convoluted meta-computing.

Ubuntu ships with a nice Simple Scan app, which as the name might suggest, allows you to scan things rather simply. But for some reason I thought that getting a scanner was a good reason to start scanning every one of the numerous pieces of paper I get from school. Naturally, there’s a problem of course which arises from the fact that I have to open up an app (usually with the absurdly slow unity launcher) and then use my mouse to click buttons, all of which happens on top of the already undue burden of opening the scanner lid to put papers inside.

Obviously this system would be untenable for a mass scanning addiction. Maybe a reasonable person would at that point take a deep introspective about the end goal of such an endeavor. Maybe wasting the 5 Gigabytes a year needed to archive some 8,000 school papers (assuming that the files are stored at a fairly reasonable 200dpi as jpegs averaging around 5MB per)- most of which illegible chickenscratch anyway, plus the ten minutes or so per day at minimum to shuffle papers around. Well, a _reasonable _person would take into account the cost and relative benefit of such a scheme and decide that this really isn’t worth it.

But of course, I couldn’t be so overtly dismissive if I had that same reasonable sense. Obviously this setback was not a serendipitous invitation from providence to investigate the social, ethical and utilitarian merits of the goal (I say this of course with a great deal of sarcasm, but there are many less trivial opportunities that technologists ignore). Instead, ignoring whether or not it was a good idea in the first place, I decided to fix it.

The first step was trying to get the buttons to work. Canon scanners, and presumably all other scanners, have little buttons on the device that you can push to accomplish certain easy tasks. On Windows, it’s pretty cool because it’ll automatically launch whatever app it is that scans things and start it automatically. There’s a set of four: PDF, Auto, Copy and Email, pretty self explanatory at that (and if that fails to suffice, they’re coupled with cute monochrome icons).

The problem is that it doesn’t work automagically, at least on Linux. I found little project called scanbuttond, or something to that effect, and tried patching it in some way that would fix it, but after investing an hour or so- I pretty much gave up.

The thing is that having button isn’t even the most efficient system for document scanning. So what physical cues are there to indicate intent-to-scan? The first and most obvious one is the presence of a document in the bay. It’s a bit difficult to divine when a document is placed on the surface, though it’s probably possible with some fancy arrangement of lasers or light sensors exploiting ftir or precisely measuring the weight of the entire scanner or monitoring the butterflies in proximity for fft’d wing flaps. Plus, chances are that immediately after a document’s been placed, you probably want some time to adjust the paper’s alignment and get your fingers off the paper (before the intense searing beam of panchromatic LED light reduces your fingertips to burnt crisps).

For flat documents, most of the time when that happens, you close the lid so that the foam white lid insert will press down on the document (flattening out the wrinkles endemic to a haphazard backpack-paper-shoving technique) after making adjustments to ensure proper alignment. The only problem with this scheme is if you’re scanning some thicker document (a book- whatever that is) or don’t feel like lowering the lid (now, why would you want to do that?).

So with a piece of folded up aluminum foil and foam and some judicious application of tape (in a setup eerily similar to that door alarm that I built from a kit from the Discovery Channel store when I was 7) I crafted a little switch mechanism that activated whenever the lid was closed. Then the two prongs of the foam switch were attached to a voltage divider on and Arduino Leonardo board so that it could measure when the thing closed or opened. A tiny piece of code ran on the Arduino which would do exponential smoothing on the voltage between the pins and send a signal over serial.

On the computer-side of things, there’s a little python script which listens on the serial device for whenever the lid has closed. It uses the pySANE bindings to scan the document and then using PIL compares it to a blank scan in order to figure out if what we scanned was actually empty. If it isn’t empty, then it saves it to the disk as a file named after the current date.

Twenty lines of Arduino C, and a hundred of Python later, I have a scanner which makes it exceedingly easy to digitize my paper trail. Too bad I haven’t used it in four months. I reinstalled Ubuntu at some point and never quite bothered setting it up again (even though it would only entail like two lines to attach it to the startup applications list). Even when it was working, it took some amount of work and offered almost no immediate benefit- it didn’t integrate any form of OCR or fancy visualization which could potentially make this interesting from a scientific perspective. But school is winding down, I mean literally graduation is a smidgen more than a week away, so I’m not exactly going to have much more paper to digitize. So I guess this marks the end of a failed experiment, the pre and post mortem- interesting in that it succeeds in just about everything I set out to do, but I never quite got it into using it.

Maybe you’ll find it more useful than I did.

Introduction to the Pedant 07 October 2012

Recently, I’ve been racking up on hobbyist electronics components from Sparkfun. Actually, this has been going on for quite a while, and most of that spending was justified by this project, which currently has the working name of the “pedant” (which is like at least a three-layered pun). I won’t say that it’s my very first foray into building some actual piece of hardware, but it’s probably the biggest and most original hardware project I’ve ever attempted.

I probably won’t be able to sell you on what it is, because it’s actually quite simple and uninteresting in principle. So instead of selling you on the cynical summary of its functionality, I’ll gild the concept with buzz words and try my very best to instill the same kind of enthusiasm I have for this project (which might just be because I haven’t done anything before with e-textiles or other electronics stuff).

The pedant is my foray into augmented reality, hopefully that means that it’s, at least some ways, original. It’s cheap, though actually in retrospect, not nearly as cheap as it should have been. And probably the most interesting aspect is that it skips through the whole perceived evolution of augmented reality from some bulky extremity into something sleek and unobtrusive. That’s not technically untrue, because the actual device will be fairly bulky, but it would exist in an already considerably bulky device (a shoe), so the net effect is that it’s sleek and unobtrusive.

I can’t say I was into that whole augmented reality thing before it was hip and cool. I only got interested in it fairly recently, likely due to somewhat high profile forays by Google and others. In mid-to-late 2008, I had just gotten my iPhone and I was deeply attached to it. At one point, I was on a vacation and at one point there was some arbitrary fact which came into question, at which point I pulled out my glorious first generation iPhone with its pristine anodized aluminium backing and loaded an app which searched an offline copy of all the textual content in the English Wikipedia (a concept which I had become so attached with that I ended up making Offline Wiki for the same reasons). And as the question was settled, the new subject of conversation was how incredible it is to keep all the world’s knowledge in a palm sized device.

But that’s not just an anecdote about the marvels of technology, it’s also a sad tale about how distracting it was. Somehow having access to that information allowed whatever pedantic instincts to prevail, shifting the conversation from a meaningful discussion into an artless digital query. And even forgiving that fact, it was slow and distracting, destroying the asynchronous exchange of ideas by creating this handheld bottleneck. Yes, we got an answer, but at what cost?

And I think that is a beautiful way to frame the argument for augmented reality. That whatever reality we have now is already being corrupted by the influence of the virtual world, and that only by willfully acknowledging that they both share the same space, can we start in the right direction of fixing it. That’s the direction Google’s Project Glass is headed, and I think that’s the right way.

The approach taken by the SixthSense project and by Google Glass mainly interacts with the user in a visual manner. And for the latter, there isn’t any really “good” and unobtrusive way to interact with that information. Both of the projects have extremely high output bandwidth (conveying information by projecting it into the user’s eye in one way or another), but limited input bandwidth and still fairly non-discreet (waving hands around to form shapes and sliding a bar on the frame, respectively). The Pedant takes a different approach by focusing on tactile input and output. This places the project more in the league of people who implant magnets under their skin by hijacking the sense of touch to convey information about the surroundings.

It’s going to be a tiny device which fits within the dimensions of a shoe insole including an Arduino Pro, a Bluetooth Mate, an Accelerometer, 2000mAh LiPo battery, and three or more vibration motors. By tapping the foot (or by orienting it in slightly different ways) the user can input data in a manner similar to the telegraph. However, nothing necessarily restricts it to being sent through a single “stream”, so it could end up more like a chorded telegraph (a la chorded keyboard). The great thing is that with chording, it becomes much more practical to receive information at reasonable rates.

Just like how a cell phone can vibrate to signal that the user has been left a message, the pedant would be used primarily to handle notifications, but rather than indistinguishable general sensations on the thigh, it’ll portray the type of notifications as well as the content, and the user even has the possibility to respond without changing the environment.

Without weird tactile abstract character sets, the Pedant could be interesting just as a sort of social network where users can feel the presence of other users in their general vicinity. It could monitor the footsteps of all nearby Pedant wearers and as it’s connected via a cellular data network and a smartphone GPS to trigger the specific vibration motors to evoke an awareness of how fast they’re walking and what general direction they are. In a sense, a social network of pedometers.

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.