Because of the separated pin plugs, this cable is ideal for powering and connecting up to the debug/login console on the Raspberry Pi or BeagleBone Black. Connect the pins as shown to power the Pi or BBB and establish the RX/TX link. Then install the Windows XP/Vista/7 or MacOS X PL2303HX drivers on your computer and connect with a terminal program at 115200 baud.
There are four wires: red power, black ground, white RX into USB port, and green TX out of the USB port. The power pin provides the 5V @ 500mA direct from the USB port and the RX/TX pins are 3.3V level for interfacing with the most common 3.3V logic level chipsets.