Day: September 19, 2018

Braille On A Tablet Computer

September 19, 2018 by 14 Comments

Signing up for college classes can be intimidating, from tuition, textbook requirements, to finding an engaging professor. Imagine signing up online, but you cannot use your monitor. We wager that roughly ninety-nine percent of the hackers reading this article have it displayed on a tablet, phone, or computer monitor. Conversely, “Only one percent of published books is available in Braille,” according to [Kristina Tsvetanova] who has created a hybrid tablet computer with a Braille display next to a touch-screen tablet running Android. The tablet accepts voice commands for launching apps, a feature baked right into Android. The idea came to her after helping a blind classmate sign up for classes.

Details on the mechanism are not clear, but they are calling it smart liquid, so it may be safe to assume hydraulic valves control the raised dots, which they call “tixels”. A rendering of the tablet can be seen below the break. The ability to create a full page of braille cells suggest they have made the technology pretty compact. We have seen Braille written on PCBs, a refreshable display based on vibrator motors, and a nicely sized Braille keyboard that can fit on the back of a mobile phone.

Continue reading “Braille On A Tablet Computer” →

Learn To Loop The Python Way: Iterators And Generators Explained

September 19, 2018 by 17 Comments

If you’ve ever written any Python at all, the chances are you’ve used iterators without even realising it. Writing your own and using them in your programs can provide significant performance improvements, particularly when handling large datasets or running in an environment with limited resources. They can also make your code more elegant and give you “Pythonic” bragging rights.

Here we’ll walk through the details and show you how to roll your own, illustrating along the way just why they’re useful.

Continue reading “Learn To Loop The Python Way: Iterators And Generators Explained” →

Final Fantasy Exploit Teaches 32-bit Integer Math

September 19, 2018 by 18 Comments

One of the fun things about old video games, besides their obvious nostalgia, is that some of the more popular games have been pried apart and tinkered with for years, leading to a lot of new “development” within the games. This often uncovers some hidden gems that gamers might not have had any knowledge of during the game’s heyday, like this coding oddity found in Final Fantasy 7 that illustrates a lot about how 32-bit processors do math.

The original PlayStation used a 32-bit RISC processor, but the most significant bit could be used for integer signing. This means that if you have an integer that has a value of 2,147,483,647 (01111111111111111111111111111111 in binary) and you add one, the value is suddenly negative 2147483648 because the most significant digit is also an indicator of the integer’s sign. In this situation, the integer is said to “overflow”. In Final Fantasy 7, if you can somehow get a character to deal 262,144 damage in one hit (much less than two billion, due to the way the game does damage calculations), the game has a little bit of a meltdown.

[4-8Productions] had to do a lot of work to show how this glitch can be exploited in the game as well. Usually damage in this game is limited to 9,999 but under certain configurations (admittedly obtained by using other exploits and tools available for FF7 like a savegame editor) two of the characters can deal more damage than this critical value, exposing the 32-bit processor’s weak spot.

Even though integer signing is a pretty basic concept for most of us, the video is definitely worth a watch especially if you’re fans of the classic game. Of course, Final Fantasy 7 isn’t the only classic that has been exploited and reverse-engineered to the extreme. You can use a Super Mario World level to implement a calculator now, too.

Continue reading “Final Fantasy Exploit Teaches 32-bit Integer Math” →

Visual Schematic Diffs In KiCAD Help Find Changes

September 19, 2018 by 11 Comments

When writing software a key part of the development workflow is looking at changes between files. With version control systems this process can get pretty advanced, letting you see changes between arbitrary files and slices in time. Tooling exists to do this visually in the world of EDA tools but it hasn’t really trickled all the way down to the free hobbyist level yet. But thanks to open and well understood file formats [jean-noël] has written plotgitsch to do it for KiCAD.

In the high(er)-end world of EDA tools like OrCAD and Altium there is a tight integration between the version control system and the design tools, with the VCS is sold as a product to improve the design workflow. But KiCAD doesn’t try to force a version control system on the user so it doesn’t really make sense to bake VCS related tools in directly. You can manage changes in KiCAD projects with git but as [jean-noël] notes reading Git’s textual description of changed X/Y coordinates and paths to library files is much more useful for a computer than for a human. It basically sucks to use. What you really need is a diff tool that can show the user what changed between two versions instead of describe it. And that’s what plotgitsch provides.

plotgitsch’s core function is to generate images of a KiCAD project at arbitrary Git revisions. After that there are two ways to view the output. One is to generate images of each version which can be fed into a generic visual diff tool (UNIX philosophy anyone?). The documentation has an example script to help facilitate setting this up. The other way generates a color coded image in plotgitsch itself and opens it in the user’s viewer of choice. It may not be integrated into the EDA but we’ll take one click visual diffs any day!