Programming Jabber

What We’re Going to Do

Everyone knows that one of the virtues of a programmer is laziness. We’re going to extend this virtue (perhaps a little too far) and enhance it with a hacker’s innate ability to combine two favorite pastimes—programming and playing with LEGO—to build contrived but fun devices.

Often being a key part of a programmer’s intake, coffee figures highly on the daily agenda. It’s important to have a good cup of coffee to keep the brain cells firing, but it’s even more important to know whether there’s actually any coffee left in the pot. Going over to the coffeepot to find out is time away from the keyboard and therefore time wasted. So let’s put the RCX to good use and build a device to tell us, via Jabber, whether the coffeepot has enough for another cup.

In building the device, a light sensor was connected to the RCX to “see” the level of coffee in the pot. Since the coffeepot is made of glass, light passes through it unless the coffee gets in the way, thus creating a simple binary switch:

• No (or a small amount of) light measured: there’s coffee in the pot.

• Some (or a larger amount of) light: there’s no coffee in the pot.

We want to be able to send the availability of coffee to all interested parties in a way that their off-the-shelf Jabber clients can easily understand and display.

Figure 9-2 shows the LEGO MINDSTORMS device in action. The brick mounted on the gantry is the light sensor, which extends to the glass coffeepot; a wire runs from it to the connector ...