Author: Elliot Williams

1502 Articles

Reverse Engineering Galaga To Fix The No-Fire Cheat

April 11, 2015 by 13 Comments

We didn’t know there was a cheat to Galaga, but [Chris Cantrell] did. And so he did what any curious hacker would do — reverse-engineer the game to diagnose and eventually fix the bug.

Spoilers ahoy! Go read the website first if you’d like to follow [Chris]’s reversing efforts in the order that they actually happened.

The glitch is triggered by first killing most of the bees. When only six are left, they go into a second pattern where they swoop across the screen and wrap around the edges. While swooping, sometimes the bees will fire a shot when they’re at coordinates with X=0. Now two facts: there’s a maximum of eight missiles on the screen at any given time, and the position X=0 was reserved by the software to hide sprites that don’t need updating.

The end result is that eight missiles get stuck in a place where they never drop and don’t get drawn. No further shots are fired in the entire game. You win.

So that’s the punchline, but everyone knows that a good joke is in the telling. If you’re at all interested in learning reverse engineering, go read [Chris]’s explanations and work through them on your own.

And here’s our generic plug for Computer Archaeology:

Ancient video games run on MAME or similar emulators are the perfect playground for learning to reverse engineer; you can pause the machine, flip a bit in memory, and watch what happens next. Memory was expensive back then too, so the games themselves are small. (It’s not like trying to reverse engineer all however many jiggabytes of Microsoft Office.) The assembly languages for the old chips are small and well-documented, and most of the time you’ve also got a good dissasembler. What more could you ask for?

A walkthrough tutorial?  We’ve just given you one.

Oh and PS: If you get past level 255, the game freaks out.

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Even More Emulated Microcomputers: 8080 On A Stellaris Launchpad

April 10, 2015 by 9 Comments

[Steeeve] just sent us his work on emulating a handful of 8080-based microcomputers on a Stellaris Launchpad, including the bare-metal to run Space Invaders. We know what you’re thinking: Is that all you folks are doing these days?!?!? There must be something in the water.

[Steeeve]’s build is based on the Launchpad with an external 64kB of SPI RAM, a nice little TFT display, and a built-in SD card for all of your storage needs. Add in an 8080 emulator and a keyboard and you’ve got a tiny microcomputer. (Is that redundant?)

What’s really neat about [Steeeve]’s project is that he’s cloned not just one target computer, but a whole bunch of computers including (GitHub links follow) the 8080-based UK101/Superboard, the CPM/80, and the machine that ran Space Invaders, as well as the 6502-based Commodore PET and Apple-1.  And as a bonus, you can save the state onto the built-in SD card so that you can hibernate the microcomputer and pick up right back where you left off at a later date. Snazzy.

He’s also built a library which provides an emulation framework if you want to build on this work yourself. And did we mention he can play Space Invaders? Bravo [Steeeve]!

Logic Noise: More CMOS Cowbell!

April 10, 2015 by 23 Comments

Logic Noise is an exploration of building raw synthesizers with CMOS logic chips. This session, we’ll tackle things like bells, gongs, cymbals and yes, cowbells that have a high degree of non-harmonically related content in them.

Metallic Sounds: The XOR

I use the term “Non-harmonic” in the sense that the frequencies that compose the sound aren’t even integer multiples of some fundamental pitch as is the case with a guitar string or even our square waves. To make these metallic sounds, we’re going to need to mess things up a little bit, and the logic function we’re introducing today to do it is the exclusive-or (XOR).

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TV Broadcasts From Outer Space

April 9, 2015 by 19 Comments

According to ARISS (Amateur Radio on the International Space Station), the ISS will be sending us images using slow-scan TV on April 11th in honor of Russian cosmonaut Yuri Gagarin’s birthday. Tune in and you’ll get to see 12 different commemorative images from space, and of course bragging rights that you directly received them with your radio setup.

For those who aren’t Ham radio types, slow-scan TV (SSTV) is a radio mode where the pixels in an image are sent by encoding the brightness and/or color as a tone, a lot like a modem, fax machine, or the data cassette tapes of yore.

The ISS uses PD-180 which is a color mode where each pixel’s red, green, and blue values are encoded in a pitch between 1500 and 2300 Hz. Each image takes just over three minutes to transmit, meaning you’ll have to track the ISS pretty well as it travels across the sky. But don’t fret, they send each message for around an hour, so you have a good chance to receive it. (We’ll be the first to admit that a frame rate of one frame in 187 seconds isn’t really “TV”, but that’s what they call it.)

SSTV’s use in the space program goes back even before the moon landing, but with modern software-defined radio setups, it all becomes a lot more convenient to receive. The ISS folks do this periodically as a service to the amateur radio community, so it’s a good time to try out your chops.

We’ve covered ARISS before, but Yuri’s birthday is always a good reason to celebrate the folks out there. And if you need a reminder of when to look up, this hack right here has you covered.

If you do receive some images, you can upload them to the ARISS Gallery.  Or you can just hit refresh to see them as others post them up.

The Dan64: A Minimal Hardware AVR Microcomputer

April 7, 2015 by 26 Comments

[Juan] sent us his writeup of a microcomputer he built using an Arduino UNO (AVR ATmega328p) and some off-board SRAM. This one’s truly minimalistic.

Have a look at the schematics (PDF). There’s an Arduino, the SPI SRAM, some transistors for TV video output, and a PS/2 connector for the keyboard. That’s it, really. It’s easily built on a breadboard in a few minutes if you have the parts on hand. Flash the Dan64 operating system and virtual machine into the AVR and you’re good to go.

Now we’ve seen a few 6502-based retro computers around here lately that use a 6502 paired with a microcontroller for the interfacing, but they’ve all been bulky three-chip affairs. [Juan] wins the minimalism prize by using a 6502 virtual machine implemented in the AVR to reduce the parts count down to two chips for the whole shooting match.

Using a 6502 virtual machine was a crucial choice in the design, because there are 6502 cross compilers that will let you compile and debug code for the microcomputer on your macrocomputer and then load it into the micro to run. This makes developing for the micro less painful.

How does it load programs you ask? The old-fashioned way of course, using audio files. Although rather than using the Kansas City Standard as in days of yore, he encodes the data in short and long pulses of square waves. This might be less reliable, but it sure saves on external hardware.

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Arduino IDE Forked

April 6, 2015 by 110 Comments

As if it weren’t confusing enough in the Arduino world these days, now we’re going to have to deal with conflicting version numbers for the IDE. Yup, it’s been forked. Arduino LLC is offering a recently-updated version 1.6.3 at arduino.cc, but Arduino SRL has bumped up the version number to 1.7.0 at arduino.org. The conflict in naming and versioning has not gone unnoticed.

For those of you who’ve been living under a rock lately, the company that developed the Arduino (Arduino LLC) and the company that’s been manufacturing most of the hardware (Smart Projects SRL, now Arduino SRL) have stopped cooperating, filed a bunch of lawsuits, and now maintain separate websites.

According to this article (Google translate here) the versions don’t differ by much, and the 1.7.0 IDE may even be a step backwards versus 1.6.3. It certainly seems to us that the majority of the active developers in the Arduino project have been sticking with [Massimo Banzi] and the Arduino LLC camp. Of course, everything’s open source and there’s nothing stopping Arduino SRL from porting worthwhile IDE changes across to their version of the codebase.

It doesn’t take a clairvoyant to sense that this may be in response to the warning about non-licensed boards that was included in the “official” 1.6.1 release. Nor does it take a psychic to foresee confusing times ahead.

If you’re interested in doing some code-sleuthing, have a look at the two versions and leave a comment below letting us know of any substantive differences you unearth.

Thanks [Kai], and via [Golem.de].

Arduino SRL To Distributors: “We’re The REAL Arduino”

March 28, 2015 by 200 Comments

Arduino SRL (formerly known as Smart Projects SRL) sent out a letter to its distribution partners yesterday. If you’ve been following along with the Arduino vs Arduino story (we’ve previously published two installments), the content isn’t entirely surprising; it’s essentially a tactical move to reassure their distribution channels that Arduino SRL is the “One True Arduino”. That said, there’s still some new tidbits buried inside. You can skip down to read the full text below, but here’s our take.

The Business History of Arduino

arduino_vs_arduino_tnA quick summary of the legal situation. Arduino LLC was formed in April 2008 by the original five founders to provide a corporate entity behind the Arduino project. Smart Projects SRL, controlled by one of the founders, was tasked with the actual production of the boards. It turns out that Smart Projects had trademarked the Arduino brand in Italy in December 2008, before Arduino LLC got around to filing in April 2009 in the USA. But everyone was friends, right? As long as the licensing fees keep flowing.

Fast-forward to September 2014, when Arduino LLC filed a lawsuit in Italy against Smart Projects claiming that they had infringed LLC’s trademark and that they had recently stopped paying licensing fees on their use of the Arduino name. In October, Smart Projects filed with the USPTO to revoke Arduino LLC’s trademark. In late 2014, Smart Projects changed its company name to Arduino SRL (a “Società a responsabilità limitata” is one form of Italian limited-liability company) and hired a new CEO, [Federico Musto].  Around the same time, Arduino SRL opened up the website arduino.org (different from long-existing arduino.cc) but with nearly identical style. In January 2015, Arduino LLC filed a lawsuit in the US, claiming their right on the Arduino name.

The Gist of it

In short, Arduino LLC has been working on developing the Arduino platform, software, and community while Smart Projects / Arduino SRL was the major official producer of the hardware for most boards. Both are claiming to “be” Arduino, and going after each other in court. So it’s not strange that Arduino SRL would like to try to keep its hold on the distribution channels. Which brings us to their letter to distributors.

March 27 Letter

Arduino-Distributor-Update-0A good portion of the letter reads to be a very carefully worded defense of why Arduino SRL is the true Arduino:

“Arduino Srl (aka Smart Projects Srl), as you know has been from the  beginning of the Arduino® project, the place where the ideas were turned into reality and into a business.”

This is of course strictly true — Smart Projects was certainly the largest manufacturer of Arduino boards. But it sidesteps the issue at hand in the trademark suits: whether they were simply a licensed producer of the boards or whether they’re “Arduino”.

Similarly, in the questions section of the letter, they ask if there are actually two “Arduino” product manufacturers, and answer “not really”. Of course, that’s true. Arduino LLC doesn’t manufacture boards, but exists to license their trademark out to fund development.

The only real news in the letter is that Arduino SRL is replacing its old distribution and logistics company, Magyc Now, with a new one named CC Logistics. Both Magyc and CC Logistics are named as defendants in the US lawsuit filed by Arduino LLC, so it’s unlikely that this change is due to legal fallout.

What this Means

In conclusion, Arduino SRL’s letter to its distributors seems to essentially follow the line of reasoning in their trademark lawsuit in the US against Arduino LLC: since Arduino SRL is doing the manufacturing and using the Arduino name, they’re the true Arduino. Whether or not this will stand up in court, or whether Arduino LLC can make its case that SRL was simply a licensed manufacturer, remains to be seen.

We’ve embedded the contents of the letter after the break. You can also download the original PDF.

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