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Understanding USB Port Pinouts



USB wires and cablesWhether we’re connecting digital cameras to our PCs or sending print jobs from our computers to desktop printers, Universal Serial Bus technology has found its way into an incredible number of our daily activities. Universal Serial Bus – or USB, as it’s more commonly called – is a hardware interface that allows peripheral devices (like digital cameras, PDAs, MP3 players, keyboards, computer mice, printers and scanners) to connect to – and interact with – a host device (i.e. a personal computer).

USB serves two main functions: to provide a path for data transfer between the host and peripherals, and to deliver electricity to low-voltage peripheral devices (a perfect example of the two actions combined would be the simultaneous “syncing” and charging of an iPod). USB cable connectors and ports are based on a 4-pin arrangement, which means that data and power transfer take place over four distinct wires, which are integrated within each USB cable.

Of these 4 wires, two are dedicated to sending and receiving data, one is used to carry electricity (up to 5 volts, or 500mA) to low-power devices, and the last one serves as an electrical ground. Each wire has a designated color for easy identification.


Standard USB Pinout Chart:

Pin Wire Color Name Description
1 Red VCC +5V
2 White D - Data -
3 Green D + Data +
4 Black GND Ground


Mini USB is a newer form of USB technology that makes use of smaller, more compact connectors. Because of its space-conscious design, Mini USB is often used for smaller peripheral devices like cell phones, PDAs and MP3 players, and can have a pinout arrangement of either 4 or 5 pins. The 4-pin Mini USB wiring scheme is the same as the Standard USB pinout detailed above, but the slightly different 5-pin setup follows the layout shown in the chart below.

Mini USB Pinout Chart:

Pin Wire Color Name Description
1 Red VCC +5V
2 White D - Data -
3 Green D + Data +
X   ID Varies *
4 Black GND Ground


*Pin “X” can vary by cable or application. In some cases, Pin “X” isn’t connected at all. When it is connected, this wire can either be attached to the ground, or used to identify and/or indicate the presence of an attached peripheral device.

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Wonderfully simple

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