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April 20, 2008

64HDD - PC hard drive for your Commodore 64

I've been searching for a way to resurrect my old C64 in all its glory, so I can someday try to introduce my son to programming. The two problems I've run into is that I've lost most of my software, and I've only been able to find a couple of blank floppies. It's only an assumption they will still hold data reliably.

I came across the 64HDD project. It's a promising looking solution to my problem, and looks like it's been actively developed since 1999. Using a DOS PC with a parallel port and a xe1541 cable, pictured above, you can supposedly use the PC as a mass storage device for the C64. Essentially, it turns your PC into a 1541 floppy drive emulator, so you can load and save files on your C64 without trying to track down a working 1541 or disk media.

It also means that you could presumably download a bunch of disk images using your broadband connection, shove them onto a hard disk, and then access everything without having to rifle through piles of disks to find the program you want to run.

Has anyone used this before, or do you have any other recommendations or ideas for bringing a legacy system back to life?

64HDD

April 19, 2008

Manipulating Mac keyboard LEDs through software

Amit Singh, the Google Mac Team hacker who taught us all how to use the Mac motion sensor as a human interface device and manipulate the keyboard backlight on the MacBook Pro, wrote a short program that demonstrates how to control the LEDs on your keyboard through a user space program:

If you have an irrepressible urge to turn these LEDs on or off through software, here is a program that shows you how. (Note that the program only manipulates the LEDs -- it will not actually cause caps lock or num lock to be engaged.) The program also serves as an example of how to do user-space Human Interface Device (HID) programming through the I/O Kit.

I'm not sure what you could use this for, but that's for you to sort out, right?

Manipulating keyboard LEDs through software
Reading and manipulating the keyboard backlight on the MacBook Pro
Hacking the sudden motion sensor

April 18, 2008

Tresling - arm wrestling game controller

Meet Tresling, a newfangled competitive sport which combines the physical challenge of arm wrestling with the mental intensity of Tetris. This video has been making the rounds. It's so over the top, I can't help but appreciate it:

The site is scant on details, but as far as I know, this represents the first arm-wrestling human computer interface. The NES brought us guns and running pads. The Wiimote a tennis racket, fishing pole, and boxing glove. If you can get past the initial craziness of Tresling, it's actually an interesting hack in that it's a completely new category of game play made possible by a clever homebrew controller.

Tresling: Arm Wrestling + Tetris

April 17, 2008

SwashBot - robot from a helicopter

CrabFu's latest project, the SwashBot, is a 3-legged radio controlled robot built from RC helicopter guts. The three servos that would normally affect the swashplate control the position of the three legs. Instead of tilting or raising the swashplate, the control inputs move the robot from side to side or up and down in a surprisingly organic-looking way. Here's a video:

I think what I like best about this is its simplicity. You could make one of these guys in an afternoon using the parts from a standard RC helicopter, some hot glue, and a few extra servo horns. I'm not sure how the helmet was made, which is arguably what makes this little bot look so bad ass, but the guts would only take a few hours to put together. Pure genius.

CrabFu's SwashBot [via Makezine]
More of CrabFu's Steam Toys

April 16, 2008

HOWTO - fix a broken NES

If blowing on the Metroid cart and shimmying it carefully into the system isn't working for you anymore, don't start looking to replace your old NES just yet. Retro Gaming Hacks author, Chris Kohler, published this video howto on repairing an old NES.

The 72 pin connector that the game cartridges plug into are notorious for becoming corroded and eventually failing. Thankfully, you can pick up a new connector for a few dollars and replace it easily using a phillips head screwdriver.

How to Fix Your Broken NES
Retro Gaming Hacks

April 15, 2008

Turn an ATX power supply into a lab PSU

With a couple hours of work, it's pretty simple to pull the power supply from an old PC relic and turn it into a pretty decent bench system for powering your electronics projects. The standard ATX power supplys that you find in desktop computers have regulated 5 and 12 and 3.3 Volt outputs with sufficient power for most small project needs. You probably have a few of these just collecting dust in the basement, which means you could have a test bench PSU for quite a bit less than the 80 bucks you'd drop for one on
eBay.

WikiHow and Instructables both have a decent howto on the subject. As always, be careful when working with high voltage electronics. Nobody wants "almost saved $80" on their epitaph, so mind those capacitors.

Convert a Computer ATX Power Supply to a Lab Power Supply
ATX -> Lab Bench Power Supply Conversion

April 14, 2008

Second Life on an Apple II

InexorableTash wrote an Apple II program in assembly that receives streaming video from a Windows PC over a 115kbps serial connection. Why? So his nautilus avatar could wander about in Second Life on hardware:

For another fun example of new software on the Apple II, check out this video of a Wolfenstein-like game called "Escape from the Homebrew Computer Club 3D". In this game, the Apple is doing all the work, no external PC needed:

Some people might say that this sort of stuff has no real practical purpose, but it seems to me it's an important tribute to personal computing history. It puts the last 30 years of technology in perspective.

I can't help but wonder about what we've got in store for ourselves in the next 30.

Second Life on an Apple II [via BoingBoing]
Escape from the Homebrew Computer Club 3D

April 13, 2008

Nice overview of the YouTube API

I caught this self-referential tutorial on YouTube today which walks you through the basics of the YouTube API. It appears to be quite simple to develop Javascript or Flash applications that can control or interact with the YouTube player, or even completely reskin the interface.

What I didn't know until recently was that the API has provisions for allowing your application to upload videos and post comments. You can even authenticate users and allow them to interact with the YouTube backend through your private application. It looks like you can do just about everything programatically except remove the YouTube watermark on the video.

YouTube Developer's Guide
Developer API Blog

April 12, 2008

Javascript Super Mario

CupBoy from the Nihilogic blog wrote a Javascript Super Mario engine which compresses down to just 14K. This includes all of the audio and sprite data for the little demo, which are both encoded within the single Javascript file.

The sprites are stored in custom encoded strings in a format that only allows 4 colors for each sprite but in turn only takes up around 40-60 bytes per sprite.
We also have MIDI music embedded as base64-encoded data: URI's. No music for IE, though, and it seems all the other browsers each have different, minor problems with it, but it sort of works.

It is by no means a complete clone or anything, it's not even an entire level and several key things are missing, such as mushrooms, Koopas and stuff. It was merely done as a sort of proof-of-concept and to see how small it could get.

Granted, you're not going to fit an entire, completed Super Mario in 14KB, but just think about what was accomplished here. The image at the top of this post is probably about 30K. In half the size, CupBoy has a rudimentary side-scroller rendering engine, music, simplified physics and collision detection, and most of the artwork for the original's first level.

Super Mario in 14kB Javascript
John Resig's dissection of the game's encoded data

April 11, 2008

Automatic outbound link analytics with jQuery

I had the challenge of adding Google Analytics tracking code to all the outbound links on a site I've been working on. There are hundreds of these links scattered around the site, so rather than try and edit a bunch of links, manually adding onclick handlers in an error-prone fashion, I decided to get lazy and write some code to handle it for me.

First I was thinking about doing some sort of regular expression search and replace throughout the site and database, but that reminded me of CSS3 selectors and their ability to do simple pattern matching. I've seen people apply a special style to outbound links this way, so after a few minutes of monkeying around with things, I now have a chunk of jQuery that will automatically track clicks on all outbound links.

Here it is, in a nutshell:

jQuery(function($){ // Match all anchor tags in the "maincontent" div with // urls that begin with "http" but don't contain the // string "yourwebsite.com" $('#maincontent a[href^="http"]').not('a[href*="yourwebsite.com"]').click(function(){ try { // Get the href url and toss out the "http://" var href = $(this).attr('href'); if ( href.indexOf("://") > 0 ) { // Track the page in Google Analytics as // "/tracking/outbound/www.somesite.com/foo" var outbound = '/tracking/outbound/' + href.split("://",2)[1]; pageTracker._trackPageview(outbound);
} } catch( e ) {} } }

With this running, all of my internal pages get tracked as usual, and any external links will appear as pageviews that look like "/tracking/outbound/www.somesite.com/foo".

If you link out to many different pages on several sites, keeping the full site url in the tracking code and building these deep paths is particularly useful. Google Analytics will allow you to drill down into the tree like it was normal content and quickly pull numbers on how many total outbound clicks you received (/tracking/outbound), how many went to www.somesite.com (/tracking/outbound/www.somesite.com), and how many people clicked out to a particular page on the site.

This saved me quite a bit of time and is immensely more flexible than any other outbound tracking method I've used. I hope this helps someone else. Drop me a line in the comments if this works out for you.

Update: it looks like I wasn't the first to do this. An article by Rebecca Murphey shows how to do something similar, while also adding the referring post title to the tracking code. Pretty cool stuff, I must say.

April 10, 2008

Silence your hard drive

For a buck's worth of materials, you can quiet your PC by damping your hard disk's vibration:

As the pictures show, the drive is essentially suspended on the stretched elastic. The resilience of the elastic stops all vibrations from passing from the drive to the case -- or vice versa, for that matter.
...

When I showed one of my suspended drive systems to my favorite local dealer, it was the complete absence of vibration in the case that amazed them the most. They could not tell when the PC was turned on by the usual vibration of the case. They found it eerie.

Keep in mind that you'll loose some of the conductive cooling that you get when the drive is mounted to the case, so it'd be smart to do this in cases where there is decent airflow or find a way to attach some sort of heatsink to the bungeed drive.

Hard Drive Silencing: Sandwiches & Suspensions

April 9, 2008

Air on the EeePC

There's a good post on the O'Reilly Rich Internet Application blog about running Air under Linux on the EeePC:

Adobe recently released the first public alpha version of the AIR runtime for Linux on labs. This is great news! I felt compelled to "geek out" with it, and was able to get AIR running on an Asus EeePC, although with a few minor issues.
The Asus EeePC runs a derivative of Xandros with KDE, which is not a supported Linux distribution for AIR. I got it working with a little help from the Adobe forums, and I'm very excited about it. I have never gotten into Linux desktop application development, but I think that's could soon change.

There's a thread on the Adobe forums that has guidance for running Air on Linux machines. It's a simple matter of downloading the SDK and running your applications from the command line using the adl command like so:

~/AIR-SDK/bin/adl -nodebug ~/app/META-INF/AIR/application.xml ~/app

The AIR runtime for Linux release notes are pretty clear that this is still a pretty alpha product with some unfinished features, but it's something, and if you do a lot of AIR or traditional Flash development, this would be a cool way to include Linux as a build target for your next desktop application.

AIR + Linux + EeePC [via Lebon Bon Lebon]
Adobe AIR for Linux
Running AIR on Linux (Adobe forum)

April 8, 2008

Relational database using jQuery and HTML tables

Here's a novel use for the HTML <TABLE> tag: storing client side database tables. Nick Kallen came up with a slick hack that uses the jQuery syntax to perform simple selects and joins on HTML tables. By using CSS3 selectors, you can easily target fields which match or contain your search terms, and Nick's jQuery-based API provides a simple query language, similar to a rudimentary SQL:

Today I was thinking aloud about Tree Regular Expressions and how they might make a nice query language for document databases like CouchDB. Someone pointed out that CSS3 selectors might make a great concrete syntax for this. One thing lead to another and I thought, why not build a relational database in HTML? So I did. I even got inner joins working.
Let's start with a few tables:
<table class="users">
  <tr>
    <td class="id">1</td>
    <td class="first_name">amy</td>
    <td class="last_name">bobamy</td>
  </tr> 
  ...
</table>
<table class="photos">
  <tr>
    <td class="id">1</td>
    <td class="user_id">1</td>
    <td class="url">http://www.example.com/foo.png</td>
  </tr> 
</table>
Now we can express some queries:
$('.users')
  .where('.id:eq(1)')
  .select('*')
This is equivalent to SELECT * FROM users WHERE id = 1
$('.users')
  .where('.id:eq(1)')
  .select('.id, .name')
This is equivalent to SELECT id, name FROM users WHERE id = 1

How cool is that? Check out Nick's blog post for an example of text search and an inner join. The API in his jquery.db.js is quite straightforward and only about 50 lines of code. Adding a sort function shouldn't be too difficult.

I'm pretty much convinced now that jQuery is black magic.

Building a relational database using jQuery and <TABLE> tags
Download the jquery.db.js library

April 7, 2008

Javascript marker clustering for Google Maps

Everyone who works with large data sets in Google Maps has come across the problem of displaying a bunch of markers in a small area. Not just an eyesore, displaying anything more than a hundred marker icons at a time can bog the browser down on a lot of platforms, Safari on PPC Macs delivering the most pain.

The solution is to cluster nearby markers into an aggregate marker when there are too many markers being displayed, or when markers are so close at a particular zoom level that they completely overlap. For extremely large datasets this is most efficiently done on the back-end, with successive AJAX calls refreshing the marker set from a PHP script that filters out the visible markers from the set.

You can also handle the clustering on the client side, using javascript to scan the entire set of locations and dynamically determine what's visible and what should be clustered. The downside is that you have to download the entire set and store it in the browser's memory, but unless you start getting well into tens of thousands of markers this isn't a big deal. The benefit to the client side method is that it's less complex, it lets you work around large result sets from back-end APIs that you can't control, and with ACME Labs' Clusterer javascript library it's extremely easy to code.

To use Clusterer, first download and include the Clusterer2.js file from the link below in your maps page. Then you need to instantiate a Clusterer object, passing your map object to its constructor:

var clusterManager = new Clusterer(map);

From there, you use it in place of the traditional MarkerManager or any addOverlay calls by calling the Clusterer's addMarker method. It takes two parameters, the marker to add, and a text string that will be listed in the cluster's contents when it is clicked:

clusterManager.AddMarker(marker, "Marker Description");

The cluster manager will take care of all the dirty work, only displaying items when they are within your view, and dynamically clustering them appropriately when there are too many on the screen at once. When one of the clusters is clicked, it will display a list of the locations inside of it. Most of what you'd want to tweak, like the threshold at which to start clustering and the icon used for representing a cluster, are all adjustable through the API via some self-explanatory methods such as SetMaxVisibleMarkers(n) and SetIcon(icon). Follow the link below for more information, or read the source for a few of the less-documented options.

Clusterer documentation
Clusterer source

April 6, 2008

Windows Mobile del.icio.us plugin

If you're a del.icio.us power user and you use Windows Mobile, you've probably missed the del.icio.us plugin that's available in desktop browsers like IE and Firefox. Dale Lane took this problem as a challenge and coded a nice little Pocket IE plugin that adds a del.icio.us submittal form to the browser's menu.

This is not as trivial as I expected - it took hundreds and hundreds of lines of code just to get a new entry in the Internet Explorer's menu that gets me access to the web browser object as an IWebBrowser2. And (perhaps especially so for someone who has been getting a little lazy with Java and C#! ), some of it is a little intricate and complex.
Still, once done I could use my access to the browser to launch my "post to del.icio.us" form and prefill it with the URL and page name of PIE's current page. From there, the form uses the public del.icio.us API to send all the info off to my del.icio.us list.

It's written in C++ and he's zipped up the full Visual Studio project. Based on the difficulty and lack of great documentation for doing something like this, this is actually a pretty solid find. If you want to make a PIE plugin, this would be a good place to start.

A del.icio.us plugin for Windows Mobile (or C++ is a pain)
Pocket IE del.icio.us plugin and source

April 5, 2008

HOWTO - Encode any string into a trigonometric function

Following Poromenos' nifty "Hello World!" function, Jan Krueger posted a great explanation for why it works along with a general method for producing a trigonometric function for _any_ string you like:

The magic behind Poromenos's function is the Fourier theorem: any "mostly" continuous and periodic function can be expressed as a sum of sines and cosines. I'm not going to bore you with the details; suffice to say that this also works for sampled functions, i.e. discrete series of values.
There's an algorithm called DFT (Discrete Fourier Transform) that takes a series of N complex sample values and generates a corresponding Fourier series which encodes the various sine/cosine coefficients in N complex output values. In the special case of real input values (which is an extremely common case), you can effectively throw away half of these output values and take the remaining N real/imaginary components, do a bit of magic, and end up with coefficients for a function of the form:

f(t) = x0 + x1 cos(t) + x2 sin(t) + x3 cos(2t) + x4 sin(2t) + ...

Now, f(2 pi n/N) returns exactly the (n+1)th character of the original string.

Follow the link and you'll find a nifty C program that will produce a trigonometric function for any string you like.

HOWTO: encode a string into a complicated-looking trigonometric function

April 4, 2008

Add keystroke user verification to Gnome

Nathan Harrington amended the GNOME Desktop Manager to include keystroke dynamics in the user verification process. When the user enters their username, the timings between key press events are measured and compared against a stored pattern. The theory is that there is a significant difference in timings for words typed by different individuals, so the way a username is entered provides a bit of extra "fingerprint" information that can be used to help authenticate a user.

I'm not sure how immediately useful this will be, since this particular example won't affect other login methods, such as an ssh session. Nevertheless, the idea is pretty cool and the code is all there for you to monkey around with.

Identify and verify users based on how they type [via slashdot]

April 3, 2008

Practical fluid mechanics

Mick West from Cowboy Programming posted a two part series to his blog titled Practical Fluid Dynamics. Originally written for Game Developer Magazine, it covers a number of clever (and down-to-earth) techniques for simulating the movement of fluids in games and other software environments where real-time speed and visual authenticity matter most.

Special attention is paid to the simulation of particulate matter being carried around within a fluid volume—think effects like smoke, fire, and bubbles. I know I've seen a number of people using particle systems to do this sort of thing, but the methods Mick describes are all based on a grid model where you represent the system with a velocity field and a density field. Unlike a particle system, these fields represent a continuous fluid surface, allowing you to measure the density and velocity of the fluid at any location on the surface by interpolating the values from the nearest cells in the field array.

Practical Fluid Mechanics

April 2, 2008

Poromenos' hello world curve

Take a peek at this curve. If you take the rounded y value for every integer x from 0 through 11, you'll have yourself the ascii values for the string "Hello world!".

Well, I have a computer architecture exam in six hours and can't be bothered, so I figured I would realize a lifelong dream of mine, and make a program that prints "Hello world!" using curve fitting techniques. Enlisting the help of a good friend with numerous mathematical papers under his belt (ostensibly because he could not afford a tighter belt), MATLAB and a longing for procrastination, we embarked on this perilous journey. After many, many hours of fitting and discarding data, I can finally present to you my masterpiece.

It's 12 characters summed from 10 sines and cosines:

96.75 - 21.98*cos(x*1.118) + 13.29*sin(x*1.118) - 8.387*cos(2*x*1.118) + 17.94*sin(2*x*1.118) + 1.265*cos(3*x*1.118) + 16.58*sin(3*x*1.118) + 3.988*cos(4*x*1.118) + 8.463*sin(4*x*1.118) + 0.3583*cos(5*x*1.118) + 5.878*sin(5*x*1.118)

Poromenos' blog has the full Python script which evaluates and renders the famous words. Hands down, this is the best math to happen to me all day.

Printing "Hello world!" using curve fitting techniques

April 1, 2008

USB CapsLocker and Sun keyboard simulation

Of all the April Fools pranks that I came across today, the Stealth USB CapsLocker was my favorite. The tiny AVR-driven USB device sends random caps lock keypresses to a PC via a USB interface. The user will see their caps lock light come on from time to time and think they've accidentally hit that most useless key on the keyboard.

Then they might see the Caps Lock light turn on by itself. Next is a sequence of reboots, bashing the keyboard on the desk, clicking through the Control Panel, possibly even replacing the keyboard. Unless they notice the tiny little device sitting in one of the USB ports on the back of their computer, nothing will help.

Equally as cruel, but slightly less technical, would be to switch someone's keyboard mapping to be like the old Sun keyboards (with the control and caps lock key positions swapped).

Be careful, though. There might be some cranky old unix guru who actually appreciates this configuration.

Stealth USB CapsLocker
EasyLogger - example AVR USB keyboard input device
Remap Caps Lock