Stokes' ProjBlog

Buttoning down security November 1, 2015

My employer recently rolled out new security policies, including stricter requirements for passwords. As often the case, strong passwords using the new scheme can be a bit difficult to remember, and the unnatural mix of symbols makes them slow to type. A system with less strict password rules paired with a physical key (the “something you know/something you have” combo) would be more secure and convenient, but it is usually something that needs to be rolled out at a company level. I came up with a compromise.

iButtons are kind of a cool technology, albeit one that never made it out of certain niche markets. Basically, iButtons are 1-Wire chips in ruggedized packages similar to coin cell batteries. They only need two connections — combined data/power and ground — so the battery form factor works well. iButtons have unique 64 bit IDs and can join a 1-Wire “MicroLAN” with just a touch to a reader. I’ve had an assortment of 1-Wire and iButton hardware for a long time but never found a good use for it… until now.
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My brain made me build a robot. June 1, 2015

A while back, I was held hostage by my own brain: it refused to let me sleep until I got out of bed and built a robot.

What prompted this was the delivery of some cheap ultrasonic range finders I’d bought. I wanted to try them out in a project; something more interesting than just displaying the distance measured, but not so complex that the range finders became secondary to the rest of the project. Eventually, I came up with an idea for a robot which was both simple and interesting. Unfortunately, this idea came to me while I was on the verge of sleep. The idea was a little too interesting: my brain refused to stop working on it, ultimately issuing its ultimatum. No robot, no sleep.

As usual with these spur-of-the-moment projects, I hacked the robot together from materials I had on-hand; the majority of my time was spent digging through my junk bin for suitable parts and matching screws. The final robot is a combination of random bits including PC case hardware, vintage Erector Set pieces, and a small bit of furniture-grade hardwood, atop a set of toy tank treads and powered by a twin gear motor. All in all, the robot’s body is somewhat unremarkable, other than having been assembled from junk by someone half asleep. The robot’s ‘brain,’ however, is much more interesting.
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Hanging on the Telephone September 25, 2013

With the Atari keypad working, I want to adapt another old input device to work with modern machines. I’m going to set my sights a bit further back this time.

When I was in my single-digit years, I was given a broken telephone to play with: a standard Bell desktop model with a rotary dial, nearly identical to the other phones in the house. I discovered that a flashlight bulb and battery could be wired to the dial so that the bulb would blink when a number was dialed. Not just blink, I noticed: blink the same number of times as the number dialed. I also noticed that the bulb was normally on, and would wink off when dialing — the opposite of the way I expected a switch to work. These observations lead me to discover that a real phone could be dialed by quickly tapping the switch hook. I suspect I dialed a few wrong numbers during my research, but I was so thrilled by my discovery that I can’t remember them now. I may not have noticed them then, either.

My new project: create a USB rotary numeric ‘keypad.’ I know this has been done before, but as a tribute to my early experiments, I’m going to do mine without any research from the ‘net. This will be a purely experimental venture.

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Check out my (Atari key-)Pad, Part 1: Hardware Archeology September 2, 2013

A while back, a surplus electronics catalog was offering vintage Atari numeric keypads. Specifically, it was the Atari CX85, introduced sometime around 1982, intended for Atari 800 computers*. I have a thing for input devices, so of course I picked up a couple. It’s a hefty unit, housed in 70s/80s earth tones, with the ubiquitous Atari unshielded female DB9 connector. Its 17 keys have a nice, chunky feel to them. My goal: get this keypad attached to a modern computer — without any permanent modifications.

One thing leapt out immediately: 17 keys. I had to recount them to make sure I wasn’t seeing things. 16 keys is typical of a keypad, with keys wired in a 4×4 matrix. Having a prime number of keys is kind of bizarre. My initial thought was that maybe it contains a 4×5 matrix and some number of possible keys are just left out; that would fit a 9-pin connector, but I realized that the keypad has to be compatible with the Atari joystick port. In addition to +5V and ground pins, the joystick port has only five digital and two analog pins: the four cardinal directions, the ‘fire’ button, and paddle inputs. What’s more, the pins are input-only, so unless the keypad switches are DPST (unlikely), there’s no way the computer could scan the keypad (supplying power to each column or row to see which button is pressed). There had to be some logic in there.
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Introducing MusicMover! July 15, 2013

The situation: I wanted to keep the music collection on my phone fresh. I use iTunes since I have a Mac and an iPad, but my phone is Android-based. This wouldn’t be a problem if my phone had enough storage for my entire library — I’d just copy everything and be done with it — but I have many times more music than my phone has space. iTunes will do some stuff to randomize the subset of music on an iOS device to fill available space, but there’s no simple bridge to Android.

The solution: MusicMover. I put together a moderately simple Python script that reads the iTunes library XML and copies tracks (to a specific total size or minimum free space) to my phone when I mount it as a USB drive. It doesn’t just copy, though: it replaces (by default) a third of the music already on the phone with fresh tracks.

It’s a fairly bare-bones, but it gets the job done. As it stands, it’s a command-line utility, with an optional Tk progress bar display. Since it may be of use to others, at least as a starting point for their own projects, I’ve put it on GitHub. I’d like to see what other people can do with it.

A display of character(s) December 8, 2009

As the W&B soda machine has been unplugged for the winter, I am putting the soda machine hack project on hold for a couple of months. In the meantime, I’m returning to some past projects, several of which I never wrote up in the blog. One such project is a system for handling and displaying an ultra-tiny bitmap font on a little graphic LCD, the sort that were on nearly every 90s cell phone and are currently popular with hobbyists.

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Blatant Fabrication October 2, 2009

I made my first tentative steps into the world of desktop manufacturing last night. Having a couple of small servo motors, I thought it would be cool to make a tiny pan/tilt rig with them. I also thought this would be a good first 3D printing project. A couple months ago, several of us at W&B got together and built a Makerbot*, a small hobbyist’s 3D printer based on the RepRap project. Like RepRap, the Makerbot fabricates objects out of extruded ABS plastic, the same stuff of which LEGO blocks are made.

The Makerbot fabricates things by laying down a thin bead of molten plastic onto a small platform. The platform moves in two dimensions beneath the extruder, creating a cross-section of the model being built. After one cross-section is complete, the extruder rises and the next cross-section begins. It is a little like creating something from cake icing — I wonder if that’s the origin of the Cupcake name.

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Random idea: unique IDs on the Arduino September 23, 2009

I was thinking about ways to create multiplayer games/toys using the Arduino platform and realized a key difficulty: telling different Arduinos apart when there are more than two. Optimally, the system should not depend on one Arduino being the ‘boss’ and should be as simple as possible for the programmer. I think I have a solution.

This is the idea: modify the pre-compiler (or, more specifically, the IDE code that calls the precompiler) to automatically include a #define statement, defining MY_UNIQUE_ID as the last sixteen bits of the build time in milliseconds. The chances of two Arduino builds being done in the same thousandth of a second are extraordinarily low, effectively making the ID unique for all practical reasons. In the code, all the programmer needs to do is use MY_UNIQUE_ID as a variable.

I’ll have to take a look at the Arduino IDE source.

Update (9/24): A couple of people have commented on this on Facebook (where this appears via RSS), suggesting some dynamic, real-time solutions. These are good ideas, but the situation I was imagining isn’t one in which all the points would have access to each other simultaneously; instead, temporary connections are being made between units, probably by physical contact.

‘The Soda Machine Hack Project’ September 4, 2009

Willoughby & Baltic has acquired a vintage soda machine; if I were to guess, it dates back to the late 1950s or early 1960s. It’s a massive steel box with a wood veneer front, its sides an industrial non-color. In contrast to more modern machines, its only text is the words Cold Drink in small, white-on-black, sans-serif lettering above a narrow, horizontal window displaying a representative can of each beverage within. I should have thought to photograph it, but I was distracted by the interior. Inside, the machine is a wonder of space-age technology: as you can see from the schematic, everything operates on 110V AC line current, and its works are almost entirely electromechanical relays and solenoids. Frankly, it’s pretty cool.

Of course, the first thing that needs to be done to the machine is connect it to the Internet. Why? I don’t know. I’m only interested in the ‘how’ at the moment.


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‘The Control Panel Project’ September 2, 2009

I’ve long been interested in UI and usability; I took some courses back in school and I’ve pursued it on my own since then. A couple of months back, I performed a thought experiment: what would be the worst (plausible) user interface hardware? It occurred to me that bad interfaces keep the user from performing an activity, but what if the interface itself was the activity? In such a case, the regular rules no longer apply.

From that came my idea for a modular, expandable control panel composed of banks of toggle switches.

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