Sub Ubi

Sadly, my Roomba arrived dead-on-arrival. I’m waiting for a UPS label to mail it back (along with the bits that fell out of its innards upon opening). Given our timeframe, I don’t think I’ll order another before going back to England.

And it looked like such a good toy, too. I had visions of plugging my Gumstix into it, and writing my own vacuuming algorithms on the Transterpreter.

This kind of email used to get me all kinds of excited:

Not any more; I’m all done with school now. (I’m still pleased that’s the case… perhaps it will wear off in a few years.)

A few weeks ago we had a Cool Stuff in Computer Science session dedicated to Greenfoot. Cool Stuff is an extra-curricular “course” open to students at the University of Kent where we explore… well, things they think are cool. Sometimes, we focus on things we think they’ll think are cool. (Did I get that right?)

Anyway, what I like about using Greenfoot in the classroom is the unpredictability of what students will do. I started things out by showing them “termites”, which is a world I created based on a world in StarLogo/NetLogo.

Termites! (~400KB MP4, click to play)

Then, I introduced them to the (mostly empty) Hippo world.

A hippo world

Now, I think the introduction matters. I sold them on hippos on the (false) belief that hippos are kind, friendly creatures that love nothing more than to wallow about in the water. Now, in truth, hippos are cantankerous creatures that are not to be trifled with. And, I think (but am not sure) that they are omnivores. They eat meat. I think.

Regardless of whether it is true, in my world, hippos eat sheep. Poor, defenseless, dumb-as-rocks sheep.

And that was it. Some introduction to how Greenfoot works, and how you actually add behavior to an Actor, and they were off. “Do something cool” was the extent of our instruction that evening.

The first world I’d like to share with you is Rage Lemons (hippos-ragelemon.zip). Below is a 2MB movie (MP4 encoded as well) of the hippos in action.

Rage Lemons! (click to play)

You see, in this world, Hippos and Sheep live together, peacefully. Until, of course, a Hippo eats a Rage Lemon! At that point, the Hippo goes bezerk, eating any and all Sheep it comes across. Eventually, the powerful effect of the Rage Lemon wears off, and the Hippo resumes its normally peaceful life.

In my last post, I talked about how we have some new documentation available for people interested in porting the Transterpreter. This documentation is, primarily, about how to use C and occam-pi together to configure hardware devices for working with the Transterpreter.

However, writing programs that involve two languages does not necessarily make life easier. Which is why I’m glad to say that it is possible to talk to hardware directly from occam-pi. In our porting documentation, we demonstrate the use of C and occam-pi to control the LEDs on a Texas Instruments MSP430-based device. What’s nice is that we don’t need C at all!

In occam-pi, we can declare a variable PLACED. Normally when you declare a variable the compiler decides on where, in memory, that variable will go. However, when working with memory-mapped I/O, you might want to place a variable there, and know that whenever you set that variable’s value, or read from it, you are reading from a particular location in memory. The PLACED keyword allows you to choose exactly where in memory that you want a particular variable to live.

You can do the same thing in C, of course… but you can’t guarantee the safety of that memory-mapped location in the context of many threads. occam-pi, on the other hand, guarantees at compile time that your program is free from race hazards.

Currently, you can see my explorations with this in the trunk of the source tree in the tmotesky wrapper. Things will move, eventually; for now, the Native subdirectory contains my explorations in configuring the Tmote Sky entirely from the interpreted language. Right now, I’m working on the SPI bus and radio configuration.

I decided that I should get a Roomba to experiment with.

The Roomba is a floor vacuuming robot; it is capable of detecting walls (with bumpers), stairs (by detecting when its wheels “drop out”), how dirty the floor under it is (with magic), and a bunch of other bits. What interests me most is the serial port on the back of the robot—you can plug in a PC or other device and control the Roomba yourself.

When controlling the Roomba, you can read from the sensors and direct it using your own control code. I’m pretty psyched about this—it’s a quick-and-dirty platform for experimenting with robotic control. By purchasing a refurb unit, using a coupon code for 20% off on robots, and using Google Checkout, I managed to get the bot for $78. I haven’t decided if I’m going to bounce it against my hardware budget or not.

Carrie said I can leave it at home when I’m not experimenting with it…

Perhaps we should have let “Intelligent Design” fly by… now, it’s just a frontal assault on science carried out by the USGS.

I wonder when DARPA, DOE, and NSF funded work will fall under similar rules?

WASHINGTON (AP) — The Bush administration is clamping down on scientists at the U.S. Geological Survey, who study everything from caribou mating to global warming, subjecting them to controls on research that might go against official policy.

New rules require screening of all facts and interpretations by agency scientists. The rules apply to all scientific papers and other public documents, even minor reports or prepared talks, according to documents obtained by The Associated Press.

It’s been a while since I’ve posted anything; this mostly has to do with the theft of my Powerbook a few months back. Since I lost ecto, I wasn’t really able to easily keep on top of weblog posting.

I’m in the States from the 6th of December until the 11th of January, and will be working remotely for some of that time. I’ll take some time off around the 25th-1st-type dates, but will generally see my email (read: SPAM inboxes) as it flies by.

The occasional post (here and elsewhere), with the purchase of new MacBook goodness is now likely. For those of you who are spec-hungry, it’s a 2GHz Core Duo with 2GB of RAM and 160GB of disk. It is quite tasty, and I like it. As the insurance company was kind enough to cover the iPod loss as well, I picked up a 1GB iPod Shuffle as well. I’m happy with that replacement as well.