Although proprietary systems and protocols abound in Home Automation, the open source movement is alive and well. xAP and xPL are open source protocols designed specifically with Home Automation in mind. Both are ASCII protocols designed for low bandwidth. It's important to note that although these two protocols are similar, they are actually different from each other and are led by different groups.
The concept is to create a protocol which can act as the glue for other proprietary protocols. Typically, a PC is used as an xAP or xPL hub and software is written to translate existing protocols such as Z-Wave or X10 to xAP or xPL. This allows messages to be sent to the PC Hub, which relays them to the intended target. The PC Hub listens on a TCP/IP port and broadcasts data on another TCP/IP port which allows multiple devices to connect to the hub at the same time.
Some hardware devices, mostly custom home-brewed devices currently, also use the xAP or xPL protocol directly and don't require software translation.
The best way to get started in Home Automation is to take "baby steps", using one of a good selection of inexpensive Starter Kits available. These kits typically come with a couple of plug-in lighting modules, a controller, and some even come with software.
Here is a short list to get you started.
Figure 11: Intermatic Z-Wave Starter Kit
After you're up and running, you can then get one of the inexpensive software controllers. HomeZix by AutomationVista.com is a Windows-only product that provides an advanced logic engine and is extensible using a C# scripting language. Currently it sells for less than $25 and supports several protocols including X10, Z-Wave and Insteon.
If you are looking for an open source cross-platform (Windows/Unix) controller, then MisterHouse is for you. It supports xAP and xPL as well as X10. xAP and xPL allow it to also support Z-Wave and Insteon along with several other protocols.
An alternative open source project to MisterHouse is HomeDaemon. HomeDaemon recently added support for Z-Wave and also supports the X10 protocol.
There have been major advances in home automation technology over the last 5 years. We have seen the introduction of many new protocols and systems and they are all fighting it out for market dominance right now.
If the past and present are any indication, we have a lot to look forward to in Home Automation's future. A recent white paper publish by Parks Associates shows the home control market as being a $3.5 Billion market in 2007 and predicted to expand to $6 Billion by 2012. Also noted was in 2007, 10% of households in the US had some type of lighting control system. Probably a much larger number than anyone would have suspected, including me.
History tells us that there is likely to be great innovations in the years to come, but at the same time there will be many disappointments. As with consumer data networking products, companies all too often announce new products and product ideas only to never deliver the goods. And when they do deliver, they are typically one or two years behind schedule.
So you need to take this into account when selecting the products you will be using. Don't count on designing your home automation network around a piece of hardware that is due out in 6 months, because chances are you will still be waiting 18 months from now.
Similarly, if you plan to use a protocol that does not currently have the device you need, find another protocol that does have what you need and make it work.
So jump in and get started! I'm sure you'll soon find Home Automation to be an interesting hobby, and lots of fun, too.
There are several online forums which are very active and may be used to get quick answers to your questions.
www.cocoontech.com prides its self for being an ad-free, independent site with no direct ties to any products or manufacturers. This site is a great resource as it does not restrict conversation and allows users to speak their mind.
www.avsforum.com is the go-to place for answers to all of your home theater questions.
Although you can get great ideas for DIY project from any of these sites, keep in mind that some opinions may be biased. Home Automation users typically have a personal preference for a protocol that is usually determined by their own situation, which typically requires a unique set of devices.
So keep that in mind when seeking advice about the "best" system to use. Just because one person has a bad experience with a product, does not mean you will too.