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SitePlayer
The most common interface at the moment on MisterHouse systems seems to be X10 followed by RS232. There are dozens of RS232 interfaces for serial, parallel, and special input/output, such as the Weeder Boards.
It is also possible to hang some input/output on the Ethernet, it doesn’t just have to be other PCs that you attach to your LAN. At a price there are LAN connected Cameras, and of course there are always Printer servers which you expect to be on the LAN. However there are now some devices marketed as mini WebServers which can be attached to the LAN. The cheapest is the SitePlayer at www.siteplayer.com with a UK supplier at http://www.totalrobots.com/siteplayer.htm
The SitePlayer is advertised as a webserver but it is much better to think of it as the equivalent of a UART (a stand alone RS232 to parallel converter chip) but for the Ethernet rather than serial interface. This is somewhat like WeederBoards or even iButton but instead of having a device address, like A, B, C as used for the WeederBoards you use a private IP address such as 193.123.23.200. It has 8 I/O lines plus a serial port, and 3 of the I/O lines can be configured as an SPI bus of which more later. For example to turn on I/O line 3 you might send it this http://193.123.23.200/demo.spi?io3=1 which tells it to set I/O line 3 to 1 and then serve you a web page called demo.spi which you have programmed into it. It is important to remember that the SitePlayer cannot execute code, it is an interface chip, but it can store and serve up lots of web pages, up to 48k total memory, which effectively makes it seem like it can execute code. By serving up eg javascript the client PC can can do the code executing for a lot of things.
A normal serial I/O chip might well have some registers which are read/write to control the I/O. In the SitePlayer the web pages effectively are used to provide a customised GUI interface instead of the registers, and this can include html, javascript, jpegs, and presumably even a .exe which would all run on your PC not on the SitePlayer.
It is just as easy to run RS232 wires to the washing machine as CAT5. However RS232 would connect to a specific computer. That computer might then have a program to interface to other computers or onto the web, but if the program isn’t running the washing won’t get done. However with a SitePlayer the washing machine is connected to all the computers on the LAN and via a router / cablemodem it can be connected to the whole world. Then using its IP address it can be contacted by any computer, not just one, and with its web page serving feature will present an interesting control interface allowing it to be turned on from anywhere in the world. Note that the SitePlayer does not actually work the different bits of the washing machine cycle because it cannot itself execute code, all the SitePlayer does is use a relay to turn it on. Remember it is just an interface chip.
The standard chip has RS232 & 8 programmable pins. Apart from the usual I/O 4 of these lines can be programmed as pulse width modulated PWM outputs which can be smoothed to effectively give D/A which can be used for lamp dimming, eg with http://www.velleman.be/kits/k8003.htm A wide range frequency can be produced from a 16 bit counter, and pulse counters are possible.
For added communication the SitePlayer is able to send and receive data using the UDP protocol over the LAN/Web. ( Sorry no more explanation here as I don’t understand UDP).
To expand the I/O, 3 of the lines can be designated for a SPI interface. This uses clock, data in, data out plus individual enable lines per chip to send serial synchronous data to special I/O chips. This bus was invented by Motorola and has similarities to Microwire and I2C. There are a lots of chips that use this simple bus, such as 8 line relay drivers, 28 line LED drivers, memory, clocks, A/D and D/A devices right up to a multiport 24 bit A/D converter made by Linear. Lots of chips can be connected, but each needs a separate enable line. That is no problem as one SPI chip could provide 32 enables for other chips, with the complication that you need to send a selection command to this chip first. Also the LED drivers can be daisy chained to give say 112 lines using just 3+1 pins from the SitePlayer.
There is a forum at http://groups.yahoo.com/group/siteplayer/
The core of Siteplayer is a tiddly board, one inch square, which needs an Ethernet connector, and maybe other connectors. The development kit is a good starting point as it also provides a couple of LEDs and switches aswell as these connectors.
Here are some SPI chips, I haven't tried them yet, just surfed the web to get you started. If you find one add it to the list. MAX6957 28 LED driver http://pdfserv.maxim-ic.com/arpdf/MAX6957.pdf LTC1598 13bit 8 channel A/D http://www.linear.com/prod/datasheet?datasheet=126&product_family=atod MC33880 8 way driver with PWM http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=MC33880&nodeId=02M0ylfWcbfM0ywyWrRn