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You’re throwing a party for the Game Developers Conference and you think it would be cool to have a custom game. What’s the natural response? How about Pong that adapts its difficulty based on how drunk you are!

Among my numerous interests is custom hardware for games and interactive art. When my friend and coworker Matthew Wegner suggested the idea of making a breathalyzer peripheral for a party game at GDC, how could I respond with anything but, “Hahahaha, Hells YES! I am ON that!”

I started by researching the various consumer breathalyzers. In the end I decided to hack the Alcoscan AL2500. It provides readings within a reasonable error tolerance and costs about $30 on Amazon — much cheaper than fuel cell meters. Upon opening it up, I found that it’s set up pretty simply. It’s driven by an ATMEGA48V-10AU microcontroller, with the semiconductor sensor connected to an analog input, and digital outputs that drive a simple seven-segment style LCD.

As I saw it, there were basically two options for obtaining the data from the breathalyzer and sending it to the computer. On the one hand, you could read the analog value from the breath sensor, or on the other hand, you could reconstruct the LCD digits from the digital outputs. Since the analog circuit driving the sensor was a little complicated and beyond my expertise (and I’d procrastinated enough that learning more before GDC was out of the question), I decided to reconstruct digits. I first followed traces on the PCB to find which pins on the microcontroller were driving the LCD. I then systematically grounded each pin while turning the unit on to determine which pins drove which LCD segments.

I then soldered wires to the relevant LCD outputs on the board (the connectors were nice and big compared to the microcontroller pins). I spent a bit of time determining which outputs from the LCD I wanted to read. As it turns out, you only need five segments from a seven-segment digit to determine the numerical value of the digit — the bottom and bottom right segments are superfluous (see Matt Mets’s recent post, who solved the problem independently). I ran a total of eleven wires — two digits for the BAC level and one wire for the “Wait” indicator — into digital inputs on an Arduino Diecimila. The Arduino code ended up pretty simple — it reconstructs two digits and the status of the “Wait” indicator and transmits these serially via USB.

I then read the serial data in using the Java RXTX library and spit it into a text file, which I then read in from Unity. The game then makes the paddle size larger the drunker you are!

The hardware is of course begging to be used in other ways — how about a program that locks you out of Ecto and your forum accounts when you’re right trashed? No more embarrassing comments that you can’t take back! I may go back and make a more sophisticated game in the future — Pong was about the right scope for the single day of development time I had left after handling the hardware and serial transmission!

I’ll have the game up for play at the 9Bit indie games party Tuesday night — if you’re at GDC just find folks from Flashbang, Gastronaut, or ThatGameCompany to get an invite and drink tickets! I’ll post an Instructable and some more information about the software when time permits. Extra special thanks to Becky Stern and Matt Mets for their advising on the hardware interface!

Ever since I replaced my laptop with a MacBook in January of this year I’ve been impressed with Apple’s OS X - in fact I’ve moved over to using it entirely, having replaced my desktop with a Mac Pro in July. It has a very snazzy interface and overall good user experience, and underneath all that prettiness it’s running on BSD so I can hack away via terminal all I like. However, coming from a Linux background, I’ve found the color options for the default BSD ls command lacking. With the GNU ls, you have a very large degree of control over how things look by using the .dir_colors file in your home directory. With that in mind, I decided to replace the default ls using this simple method.

First, install XCode Tools, found on the original OS X disc. Alternatively, you can download it from Apple, though it’s about 1GB. There are a number of useful developer tools included, but what you really want is gcc, the GNU C Compiler. (If you do much programming, you’ve probably already installed this) The idea here is we’re simply going to compile the GNU ls and dircolors for our Mac. If you’ve used Linux much, you’ll recognize the steps exactly.

Next, download the newest version of coreutils from the GNU FTP. Pop open a terminal and make a temporary directory, then decompress the archive - for instance tar -xvjf coreutils-6.9.tar.bz2

Enter the directory created from decompressing coreutils. Now we’ll compile for our system. Simply run ./configure and then make when it’s done. If either configure or make gives you any guff, you probably just need a new version of XCode Tools/gcc.

Presuming that all went well, we’ve now got a new ls binary ready to go. To backup your old one (and its man pages) and replace it with the new, simply run:
sudo mv /bin/ls /bin/ls.bak
sudo cp src/ls /bin/ls
sudo cp src/dircolors /bin/dircolors
sudo mv /usr/share/man/man1/ls.1 /usr/share/man/man1/ls.1.bak
sudo cp man/ls.1 /usr/share/man/man1/ls.1
sudo cp man/dircolors.1 /usr/share/man/man1/dircolors.1

Don’t forget to trash the coreutils directory once you’re done with it.

Now all you need to do is run ls --color=auto to get colored output. I suggest adding the line alias ls='ls -hF --color=auto' to your .bash_profile file. This makes ls color-code output, as well as giving helpful symbols to indicate executable/directory/etc status and displaying file sizes in a human-readable format.

To get the full benefit of the color system, you’ll also want to create a .dir_colors file in your home directory, and have dircolors run when you start a shell. Add a line to your .bash_profile such as eval `dircolors`. You may download my .dir_colors and modify it if you like. With all that done, you can get pretty results like this: