Ian Lesnet sent in a link to his Bus Pirate project, a universal bus adapter that lets you interface with most standard integrated circuit serial protocols at different voltages – all from you PC’s serial port. The idea is that you can debug, test, and prototype ideas a lot faster if you don’t have to breadboard an interface circuit every time you work with a new chip.
the bus pirate is a serial terminal bridge to multiple ic interface protocols. we type commands into a serial terminal on the computer. the commands go to the bus pirate through the pc serial port. the bus pirate talks to a microchip in the proper protocol, and returns the results to the pc.
all pins output 3.3volts, but are 5volt tolerant. on-board 3.3volt and 5volt power supplies are available to power the connected chip. software configurable i2c pull-up resistors complete the package.
the serial terminal interface works with any system: pc, mac, linux, palm pilots, wince devices, etc; no crapware required. we considered a usb device, but usb isn’t compatible with the huge number of hand-held devices that have a serial port. we also wanted a 3.3volt device with 5volt tolerant inputs, but most popular through-hole usb microcontollers were 5volt parts (e.g. the pic18fx550).
The device supports i2c, spi, uart/serial, and raw 2-wire and 3-wire. It looks like a pretty handy little tool, and Ian has included all the information you need to build one of your own.