Hardware Reference
In-Depth Information
But, as I've mentioned previously, the CPU required for most of your HA tasks is so minimal that these are perfectly
suited to it. They also make good secondary servers in cases where the building itself doesn't allow for a single
machine in Node0 to reach the entire house, as can be the case with X10 messages and wireless communication.
Furthermore, because the power usage of these devices is often 10 watts or less, they are efficient and add very little
overhead to an existing setup.
The specifications of these machines differ wildly, because many include custom hardware to improve on the
apparent capabilities. The Fit-PC2, for example, includes only a low-powered Atom processing but is able to play back
HD 1080p H.264 video by incorporating hardware acceleration. 3
The biggest downside with these machines, however, is the lack of bravado when demonstrating your HA setup
to friends. After showing how you can e-mail your light switch, send a text message to your video, and have your own
home web server, opening a cupboard to show a small box that fits inside your hand is often a letdown for the male ego!
Custom Embedded
This group features both system-on-a-chip (SoC) machines and single-board computers (SBCs), of which there
are many, including the Mini-ITX machines you saw earlier and the NSLU2 from Chapter 2. There are as many
combinations of devices as there are uses for machines, so each needs to be considered on its own merits as the
various components one often considers standard on a PC, such as a keyboard, mouse, and monitor, are not available
on all SBCs such as the Gumstick. 4
Also, some machines, such as the NSLU2, can have issues with seemingly normal peripherals, like USB hubs,
and refuse to work with them. Consequently, these types of device are usually better suited to client machines in
confined areas of the house, rather than servers, because the server will be running a wide range of software where
any annoyances of hardware incompatibility will generally outweigh the benefits of size.
Raspberry Pi
Although the Raspberry Pi is conceptually no different to any of the custom embedded devices you might have
discovered form the section above, it is not quite the same. Primarily, the fame and market acceptance of the Pi has
ensured a solid user base which other platforms can't manage. Having now reached critical mass in the marketplace
means that any problems you might find will have be solved by more than one person, and will have (at least) one web
page, or forum thread, dedicated to the solution.
This mass of users has also meant that the main physical problem of using a Pi as a server has be solved—the
case! It is possible to buy several different types and styles of case from the various sites on the Internet. This
includes the list at http://elinux.org/RPi_Cases that also details some you can build from LEGO, wood, and with
3D printers.
Power Consumption
For many, home automation is likely to be the first time you need to consider the total cost of ownership (TCO) of a
machine by factoring in its power usage. This can be computed empirically by using an electricity usage monitor, like
Kill-A-Watt ( www.p3international.com/products/special/P4400/P4400-CE.html ). Such a device can be plugged
4HEDRIVERSFORTHISARECLOSEDSOURCEBUTAVAILABLEFOR,INUX
4HESEINCREDIBLESMALLMACHINESMEASURELESSTHANASTICKOFCHEWINGGUM3EE www.gumstix.com
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