arduino

Mercury-bound space craft, adding MIDI to everyday objects, and the software running ludicrously-complicated automated painting machines. Dorkbot DC doesn't fail to bring interesting stuff. Tom and I had a great time seeing these projects.

It started off with a talk about the MESSENGER probe. Katie Bechtold is a software developer who works on the X-Ray Spectrometer, some other sensors I can't remember the name of, and some day to day behind-the-wheel space probe driving. She brought along a 1/10 scale model of the probe and did her best to point out where the various sensors and crucial parts are. The model was probably two feet tall, if you want an idea of how big it is.

Her explanation of everything was great for those lacking a background in astrophysics (hint: me). I won't say much about the actual workings of the probe, as I don't think it's appropriate to do so until Echoditto is in the business of slinging extremely complicated computers off to distant planets. Here's what was really neat to me:

I really liked that movie Sunshine. Mercury is pretty darn close to the sun, and MESSENGER has to be protected from it at all times. That means there's a big sunshade the majority of the craft lives behind. It isn't even to Mercury yet and it already hits 700 degrees Fahrenheit on the surface of the shade! Bonkers.

On Wednesday Ben and I headed over to the monthly meeting of Dorkbot DC and soldered our little hearts out. I've only been to one Dorkbot before (well, unless you count the one at SXSW — but that was mostly an opportunity to buy t-shirts and drink free beer). My previous experience had been enjoyable, but maybe a little dry. It's inevitable that the speakers won't pique everyone's interest every time, I suppose.

This meeting was a lot more fun, and a lot more hands-on. The organizers did a fantastic job, preparing instruction material, assembling kits and even pre-drilling jigs for the rest of us in an effort to introduce the extremely large crowd to soldering by way of MAKE Magazine's LED cube weekend project, slightly modified to work with an Arduino.

Sure, it's a simple project, but we've never claimed to be electronics gurus. Besides, it was a great opportunity to refine our soldering skills — something I'm in sore need of after nearly trashing my Wii during a botched modchip installation.

Wow. For the first time in my life I've undertaken an electronics project and had it immediately work. I'm still a little shaken by the experience.

As you might recall, in my last post I discussed loading the custom, Linux-based DD-WRT firmware onto the Fonera router. I left off with some thoughts about using that environment to achieve serial communication with an Arduino.

Getting the Fonera to talk to my Arduino turned out to be shockingly easy. The 2200 Fonera model has a four-pin header exposed. The pin closest to the ethernet port is ground; next is serial receive; then comes serial transmit. I scrounged up a female pin header connector from a USB break-out bezel I had lying around (already half-cannibalized — last year I'd used the USB end to make the cable necessary for softmodding the office Xbox). That makes the photo to the right look a bit messier than it needs to. In truth I simply connected ground to ground, then the Fonera transmit pin to the Arduino receive pin.

The Arduino software environment's serial monitor only displays transmitted data, so I whipped up a quick program to read incoming data and echo it back out on the transmit pin (which wasn't connected to anything, but the Arduino's serial output is picked up by my macbook through the USB connection). You can see the program in the picture below. You can also see the result I got when booting up the Fonera:

It worked! First you see the bootloader, then a bunch of garbage. That's nothing to worry about, though. The bootloader runs at 9600 baud, which is what I had the Arduino serial link configured to expect. Once the bootloader is done, the DD-WRT environment takes over, and it ramps the serial port's speed up to 115200 baud, producing the cloud of gibberish that follows the bootloader.

Fortunately, that's easy to fix with the stty command:

All of us at EchoDitto are big fans of the FON project — we run a FON access point here at the office, and I run one at home even though my primary router is a much-more-capable WRT54G running an old version of the Sveasoft Linux firmware. I got my Fonera router from Phil, so I assume he's running a FON AP, too. We're trying to support the project — honest!

I say all this out of guilt. Last night I hacked a Fonera. I know, I know — they sell these things for next to nothing only so that they'll get distributed and the project will grow. But I don't have any more WAN pipes available to share! So I hope the project's sponsors will forgive me for succumbing to the siren song of $10 Fonera routers on eBay. I couldn't help myself from checking out what a spare unit can do.

"Kind of a lot" turns out to be the answer. The La Fonera is based on the Atheros chipset, which is found in a number of other commercial routers and supported by both the DD-WRT and OpenWRT firmware projects.

Sveasoft kicked off the custom router firmware scene, but the author's controversial attitude toward the GPL made them fall out of favor rather quickly. Besides, truly open efforts quickly outpaced the project. OpenWRT is the king of functionality, but also the most intimidating — they seem to have a general "GUIs are for chumps" sort of attitude. While I aspire to similar levels of snobbery, I'm more comfortable sticking with projects that have support forums filled with posts that are comprehensible to someone just getting started with the project.

Besides, I've had great luck with DD-WRT in the past, using it to successfully repeat a neighbor's faint wifi signal through my girlfriend's apartment (with permission, of course — but without having to do anything to his router, i.e. no WDS).