This cable enables access and data exchange between PC/Mac and Raspberry PiÂ/Microcontroller via a terminal program. Furthermore, the cable also provides a power supply. Thus, no additional power supply unit is required. Construction of the cable Inside the USB connector is a USB serial conversion chip (PL2302HX) and at the end of the cable are four wires - red for power, black for ground, white for RX into the USB port and green TX out of the USB port. Power supply via USB The red power supply pin supplies the 500mA directly from the USB port - so no separate power supply is necessary. The RX/TX pins have 3.3V levels for connection to the most common chipsets with 3.3V logic levels.