Skip to main content

Interactive OLPC XO Display Simulation


Many people still have not seen the innovative display of the OLPC project's "XO" laptop. It has twice the resolution of a regular LCD (200 dpi), and works in bright daylight in gray-scale reflective mode. It's impossible for me to increase your screen's resolution by software, and I cannot make your display reflective, but here is an interactive simulation of the backlight mode with its interesting color pattern. This pattern is the source of a lot of confusion about the "color resolution" of the display. The LCD has 1200x900 square pixels, but the backlight puts a full color through each pixel. It is not made of red, green, and blue sub-pixels like a regular LCD, but the first pixel is full red, the second green, the third blue, and so on. The DCON chip (Display CONtroller) selects the color components from the full-color frame buffer.

My simulation of the DCON achieves the same effect by selecting either the red, green, or blue color component in each pixel. Just move the mouse pointer around to see how different colors are reproduced. You'll notice strong diagonal patterns, but remember, on the actual display the pixels are only half as large. Note that the actual DCON optionally applies a bit of anti-aliasing in hardware which is not simulated here. It helps reproducing fine structures and depicts colors more accurately. Additionally, the simulation shows a magnified image to better illustrate the principle, but it is not accurate because the reflective area of each pixel is not depicted. Maybe I can add this in a later version.

I made the simulation using Squeak / Etoys, which is one of the programming environments on the OLPC machine, but also works on Windows, Mac OS X, Linux, and many more systems. If you run the simulation on the actual laptop (download the project, place it in /home/olpc/.sugar/default/etoys/MyEtoys, run Etoys, choose Load Project), then you should close the small simulated screen and just leave the magnified view open.

For the interactive simulation, download Squeak (this version installs both, a regular application and a browser plugin), then click here to run the simulation in your browser, or download the project file, launch Squeak, and drop the project into it.

Intel-Mac users
beware, the plugin is not supported directly yet. To see the project in Safari, you have to quit Safari, set it to open in Rosetta (select Safari in the finder, press Cmd-i), and reopen. Or, use the download method, Squeak itself is running fine on Intel Mac, it's just the browser plugin that's making problems.

Comments

Unknown said…
Thanks for the tip to Intel-Mac users! I have been very frustrated with failing to run project files on the web but yours worked flawlessly, even popping up directly in my running non-Squeakland image. Great!
Darius said…
Great idea to post eToy simulations. I read blog entries complaining that XO isn't user tested. An eToy simulation might get more useful feedback, and at least, quite the complainers.

Best of Luck,
Darius
Anonymous said…
Could you please post a youtube version as well? I really dislike installing plugins just to watch demos...
Vanessa said…
Hansi: That would defeat the whole purpose of an interactive simulation, wouldn't it? Besides, you really need a 1-to-1 mapping of simulated pixels to screen pixels, not a blurry scaled video.

You can probably tell I dislike the couch-potato TV nature of youtube. Besides, to watch a video on youtube you need a plugin, too. And I actually described how to run the project without a plugin - just download Squeak from squeak.org and load the project.
Well from this we can clearly see the evolution of technology. I mean to have something upgraded So much from its original prototype model is simply amazing! What I also like about it, is since this has actually been around for a while, it gives its company higher authority since its company has focused on this specific product for quite a while already. Technology as we know it today has gone beyond advanced and to some of us, beyond the knowledge that we may even grasp!! But, to the younger crowd or to those who are still computer savvy, technological advances are really impressive

Popular posts from this blog

Frontend-only Multi-Player. Unlimited Bandwidth. Or: What is Croquet.io, really?

A multi-player web app needs a backend, right? What if I told you, it doesn’t? Read on for how Croquet gets rid of servers running your multiplayer code. No, really . Instantaneous Shared Experiences  is how we describe Croquet on our website. And while that excellently describes What Croquet does, as Croquet's Chief Architect, I wanted to share a bit about How we do that. So I wrote a Twitter thread . Here it is in blog form, slightly extended. Click the animation above if it does not play automatically Croquet lets you build completely client-side multi-user web apps. Read that again. Client-side. Multi-user. No I’m not kidding. I built it, I know it works. 😁  Croquet apps run completely client-side: are hosted as a static web site no server-side code needed no networking code needed  Croquet is literally virtualizing the server: Instead of running code on a server (or in a serverless function) we run it as a virtual machine (VM) on each client.  Croquet carefully control

Deconstructing Floats: frexp() and ldexp() in JavaScript

While working on my  SqueakJS VM, it became necessary to deconstruct floating point numbers into their mantissa and exponent parts, and assembling them again. Peeking into the C sources of the regular VM, I saw they use the  frexp ()   and ldexp () functions found in the standard C math library. Unfortunately, JavaScript does not provide these two functions. But surely there must have been someone who needed these before me, right? Sure enough, a Google search came up with a few implementations. However, an hour later I was convinced none of them actually are fully equivalent to the C functions. They were imprecise, that is, deconstructing a float using frexp() and reconstructing it with ldexp() did not result in the original value. But that is the basic use case: for all float values, if [ mantissa , exponent ] = frexp (value) then value = ldexp ( mantissa , exponent ) even if the value is subnormal . None of the implementations (even the complex ones) really worked. I

Smalltalk Bindings for Minecraft Pi

The Raspberry Pi is a cute little computer. Quite cheap at $35, you plug in USB keyboard+mouse and a TV as monitor. And it is surprisingly capable, even for running 3D games. One particularly interesting game is Minecraft: Pi Edition . As in other Minecraft versions, the main goal is to create a world. But unlike other versions, you can not only use the tools provided by the game, you can make your own tools! That's because it comes with a programming interface. The Minecaft world is made of little cubes, and you normally place or remove these blocks by hand, one after another. This is fun, but for larger structures also quite cumbersome. For example, this rainbow here might take a long time to construct manually: But I did not make the rainbow by hand. I programmed it, using the Smalltalk programming language. It's just these dozen lines of code in the Squeak programming environment: Squeak is already installed on the Raspberry Pi, because Scratch was made in Squeak