Arduino Duemilanove in 3.3v
This page explains how to build a modified USB cable, of which the 5V power is forked to be injected into the external power connector of the arduino. When you inject 5V power into the external power connector, the board runs in 3.3v. If you want to run the ATMega328p at 3.3v, some changes in the bootloader might be needed (10Mhz instead of 16Mhz???).
- Serial port 3.3v: Since the TX and RX pins are in 3.3v, you can use the Arduino Duemilanove FTDI FT232RL chip to communicate with embedded devices in serial TTL 3.3v, such as for example routers running OpenWRT. For this purpose, the ATMega chip has to be disabled by connecting the RESET and the GND pins. You can also remove the ATMega chip to disable it.
- JTAG pinout detector: Since most of the JTAG pins on embedded routers are at 3.3v, you can use the Arduino Duemilanove to detect JTAG pins on those devices.