MobZombies Sensor Board Assembly

Wow, what a bit of a learning experience this was. That chip is an Invernsense IDG300 gyroscope. $35 a pop. And its one of these “QFN” (quad, flat, no leads) style packages which basically makes it a pain to work with. I thought I could use this technique of dabbing a bit of solder on each of the pads on the printed circuit board and then put a bit of heat to the board with hot air or an iron on each pad. It “took” but there was no electrical continuity. What I think happened is that the big center ground pad took hold, but the other leads didn’t. It seems like it should have. The alignment was good after eyeballing it. Anyway, it didn’t.

So, after taking the thing on and off a few times because of some shorts I found across a capacitor and crap, I decided to have a go with a bit of solder paste. That was something I was trying to stay away from because the paste is messy and difficult to apply to such small leads (.25mm or .01 inch). This is what you really need a stencil for, I guess.

I dabbed a bit, messed it up, dabbed some more, cleaned up, etc. I basically just put paste on the leads that are actually connected to something. There are lots of non-connects, evidently for factory calibration of the device. With the solder paste on, I placed the chip, messed with it for a bit to try to get it aligned good, which is a bit nerve wracking because I’m trying to avoid accidentally spreading the solder paste around and everything. Finally, it looks good and I put some hot-air to the area. It sort of works when I check the electricals, so I try again, finally getting something. One of the devices seems a bit out of kilter — the rates on one axis when its static seems off, but maybe that can be compensated. We’ll see.

Power, but who knows how well it works? The MCUs are fine, power is fine, the Bluetooth radios there are fine. Haven’t had the nerve to check the gyros though..Those things came on and off so many times, I toasted the board a bit.

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Human Joystick Interface

Aaron Meyers deployed this turn of phrase “human joystick” during his final presentation for the course I taught this semester — “Design and Technology for Mobile Experiences.” He’s been working hard mostly on his thesis project, Torrent Raiders, but for my class he worked on programming a J2ME version of the MobZombies game that’s been percolating around the Interactive Media Division since 2002.

I’ve been interested in expanding the kinds of interfaces we have to digital worlds, and doing so to explore what computing can mean, besides the kind of computing we assume computing means. My speculation is that, to a significant degree, the “point of entry” defines and shapes what we imagine computing is, and it will not become much more than what it is so long as our point-of-entry are a flat visual display, a small squares of plastic that we push about 2 millimeters, a ball of plastic we swish around a flat surface. It boggles me when I think that this basic setup has been around, little changed, for 15 years, and much longer if you factor the computer mouse out of the framework. Boggles me.

And it’s not for lack of effort. The Wii-style wand concept has been bandied about at any number of professional/academic research contexts. Ten years ago a music conductor’s baton was the concept behind a project that, initially, was designed to control electronic music using conducting gestures. The researcher, Teresa Marrin, became so enamored with the possibility of gesture as a computer-human interface that she saw it not only as a device that could be used as a “new instrument on which to perform computer music” but also as “a model for the design of new interfaces and digital objects.” The interesting thing is that it’s more than a 3D mouse in many regards — it’s usage context is explicit in the object. The hardware is remarkably prescient:

The sensors on the baton include an infrared LED for positional tracking, five piezo-resistive strips for finger and palm pressure, and three orthogonal accelerometers for beat-tracking. Both the infrared sensor and the baton send separate data streams (including values for absolute 2D position, 3-axis accelerometer, 3-axis orientation, and surface pressure) via cable to the tracking unit, which converts the signals to the computer.

Over the last month or so, I’ve been constructing a sensor prototype that would turn the human into a human joystick for the MobZombies game. It combines a 2-axis gyroscope and 3-axis accelerometer, a microcontroller and a Bluetooth radio to transmit the data to the game display device, a mobile phone. The motivation here is two fold. First, investigate what a mobile game can be, that evokes both traditional playground style pre-digital action. Second, set up a baseline experiment for how computing can move away from the fixed office desk and make use of human body movement as an interface.

If you haven’t seen the “trailer” for MobZombies, I recommend checking it out.


(I’ve always wanted to make one of these specimen style graphics, with the ruler and callouts? You know?)

DIY Wearable Sensor

When I first cobbled the sensor together, I was hoping to use a magnetic compass like the previous version of the game controller used. It was a bit too sensitive to the RF energy created by the Bluetooth radio and I couldn’t easily find a way to separate the two without making a large design or diminishing the capabilities of one or the other. So, I turned to a MEMS gyroscope by InvenSense — the IDG300, which is a fast little gyro. I ran some quick tests which pretty much showed me that it was plenty fast. In fact, I could probably even go slower and maybe use a lower-end unit and save a few scheckles. I quickly cobbled together a bit of code bolted onto Aaron’s J2ME prototype. Turning motion is spot-on, which was a welcome surprise.


The MobZombies human joystick style interface is fun and suggestive more than it is a tectonic shift in how we interface with our devices. But, this style of interface is coming — it’s already here in some contexts. Nokia has introduced the 5500 Sports Phone with integral tri-axis accelerometer. I’ve heard tell of mobile phones that use the camera to detect and interpret motion by computing changes to the visual field. Etc.

MobZombies is a baseline experiment because I’m actually somewhat more interested in how very broad movement can become an interface to what I imagine would be a very different kind of computing than what we have today. Broad as in extended gestures beyond semaphore antics. Why? I would like to re-interpret human activities as fodder for computational expression. But this requires shifting the general notion of what computation is, which will require more than words. It will require some designed objects that express this shift through perhaps what some will see as peculiar usage scenarios.

Why do this? Why shift what computing means? Part of that answer comes from a sense that there must be much more to what “computing can become” than smaller or faster or cheaper. But, specifically in this case, my reason for thinking and doing this is because of this thing that boggles me — that the interface for the instrument that dramatically refashioned the ways in which humans make culture — whether entertainment, leisure, maintaining and acquiring social relationships, waging war, circulating knowledge, knitting together the fabrics of societies — the whole smash..that interface is set up to make you sit down and punch little plastic best. At worst, just sit down and look at a screen. I feels incredibly protozoic. There must be something beyond that computing can become. Why hasn’t that next bit come to pass? Why is “computing” so instrumentalized and so sedentary in this way?

I like to think about an entirely revitalized notion of “mobile computing” that isn’t about a small phone with a relatively powerful computer on which you’re able to run spreadsheets while you’re out and about. I’m wondering about a kind of mobile computing that puts more emphasis on the “mobile” part of that framework, where motion, in the broadest sense, is the computational activity.

1. Teresa, M. Possibilities for the digital baton as a general-purpose gestural interface CHI ’97 extended abstracts on Human factors in computing systems: looking to the future, ACM Press, Atlanta, Georgia, 1997.

A Gyroscope Game Input Control

I’ve been playing with a gyroscope lately as a game input control element for MobZombies. The challenge is to come up with a less cumbersome sensor rig, and less expensive. The sensor will need to communicate with a mobile phone because no one’s going to buy a $2000 tablet pc to play a game. The sensor should also be able to capture forward and backward motion.

The IDG300 gyroscope seemed decent, albeit “expensive” in the context of trying to make an under $100 sensor rig. But, you know..modern times and all.

I ran a few tests to see how well it captured tight and wide turns. I think it will require lots of moving average calculations. The graphs below are 20 sample averages which have also had a 16 point moving average calculation applied to them to smooth out the rough bits.

Tight left turn, basically a slow Whirling Dervish

Forward several steps, turn left, forward several steps, turn right

So, with lots of smoothing, the data looks clean enough to be able to translate turning motion into the equivalent of pressing the “A” or “D” keys to turn your guy left or right. An accelerometer will take care of forward or backward translational movement, I’m pretty sure.

The goal here really is to get to a point of capturing enough embodied movement sufficiently to use physical action as direct input into a game. This is different from the “offline gaming” idea, and closer to the “whoosh” style input.

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MobZombies on and New Kinds of Physical Electronic Play


No, that isn’t an historical photo of children playing MobZombies..but it may as well be. MobZombies is being featured on the web site..that’s pretty cool. I’ve started helping out on the project’s evolution, mostly in the area of lowering the cost of the device. This is important. I think it’s a very simple and pretty brilliant kind of user interface that really strongly suggests one way in which electronic games can get out of the Protozoic and into something much more like traditional playground-style play. I also think it could be a great test-bed for research in that area of physical electronic play or whatever you want to call it. Play that mixes the idioms of the playground and the world of digital screens. This isn’t quite Offline Gaming, but something in between the Wii and Offline Gaming.

Why? Not because I hate regular normal video games. I like to grumble about them, and about 90% of them aren’t particularly interesting to me. But so is about 90% of most media I’d say, so it’s not like I’m hating on games in particular.

No, it’s because there are a kind of electronic game I would really enjoy playing and, like..I figure I may as well think about and build those, if only to sate my ambition to create something that I find fun and that I think would actually produce some real impactful change. Physical play is not only fun, it’s generally agreed by everyone to be important for reasons of social development and to have a healthy, fit body.

So, related — I heard David Elkind on one of LA’s local NPR shows yesterday. He had some things to say that weren’t surprising based on his thorough-going arguments about childhood development. But, still — I found it interesting to hear his emphasis on a balance of activities that are about play in the traditional, skinned-knee variety, as well as those of the new 2nd life world of networked social interaction. His new book is “Power of Play”, which I’m looking forward to reading.

For a recent paper submission, I came across this from the President’s Council on Physical Fitness and Sports, which I thought was long defunct after I stopped hearing about that fitness test we did in 5th grade where you could win a cool patch if you got up in the whatever..95th percentile. (I never made it, although I tried as hard as I could.) It’s called Taking Steps Toward Increased Physical Activity: Using Pedometers To Measure and Motivate (President’s Council on Physical Fitness), which resonates with all of the step-counting programs out there. It’s cool. Step-counting and pedometers still feel a bit like..low res. What are kids going to want, that’s cool and vibes with their sensibilities around high-res electronic games?

By the way, the Robert Wood Johnson Foundation is committing $500 million over the next five years to fight childhood obesity. Their initial grant calls in the first two years are not quite appropriate to the kinds of projects described here — more instrumented research that gives something to people to try and does measurement of results and such all. But, the topics for which they’re soliciting proposals is still pretty interesting for anyone doing research in this area, such as perception of facilities for fitness and exercise, e.g. playground and recreational facilities.

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