BeagleBoard Hardware Interfacing
This page is meant to help anyone who wants to create an expansion board to interface with the BeagleBoard. It summarizes some of the commercial options, and includes some recommendations for components for a custom board.
There are several commercial boards that may work without the need to create a custom board.
A few more options can be found on the here.
It is very important to remember that the I/O on the BeagleBoard is 1.8V I/O. Level shifting must occur to interface with 3.3V or 5V devices.
Powering the Beagle
The BeagleBoard is typically powered through the barrel connector or the Mini-USB connector. When adding an expansion board, the option is available to power the BeagleBoard from a power supply on that expansion board.
There are several expansion connectors available on the BeagleBoard, depending on the revision. All revisions have J3, a 0.1" spaced header. This is not populated by default, it is left up the user to decide which gender header is desired, and where is should be placed. There have been some indications that newer versions of the BeagleBoard will come populated with a female header oriented facing downward. It may be wise to design with this decision in mind to allow for future expandability.
There are two other headers available (J4 and J5). These are 0.05" spaced headers, and are usually used only for interfacing with and external LCD. Headers and connectors are more difficult to find. It is probably best to stick with using the main expansion header unless these signals or the additional I/O is required.
Some general information about I2C and a few compatabile devices can be found on Interfacing_with_I2C_Devices.