USB 3.0 Header to USB 2.0 Header pinout signals @ PinoutGuide.com

at the 3.0 end

USB 3.0 contains normal USB 2.0 connections. This is commonly for PC cases that have ports that don't match the Available headers. Converting from 3.0 -> 2.0 is flawless, but converting from 2.0 -> 3.0 will make your 3.0 ports active, but will only function at 2.0 speeds.

USB 3.0 Header is a 20 pin 2mm pitch header using the less common ICC pin numbering. The header has a key slot on the pin 1-10 side if enclosed.

USB 2.0 Header is a 10 pin .1 pitch header using the standard IDC pin numbering. The header has a key slot on the pin 1-9 side if enclosed. (The 10-pin IDC male graphic shown has the keying on the wrong side).

Both headers contain two ports each, and have a missing pin for filled female connectors.

USB 3.0					USB 2.0
Pin Number (ICC)	Equivelent IDC Pin #	Pin Name	Description	Port	Pin Name	Pin Number (IDC)
1	1	VBus	+5V Power	1	+5V	1
2	3	SSRX1-	SuperSpeed recevier
3	5	SSRX1+	SuperSpeed recevier
4	7	GND	Ground for Power		GND	7
5	9	SSTX1-	SuperSpeed transmitter
6	11	SSTX1+	SuperSpeed transmitter
7	13	DRAIN	Ground for Shield Drain		Shared pin 10
8	15	D1-	USB 2.0 data		D1-	3
9	17	D1+	USB 2.0 data		D1+	5
10	19	NC
11	20	D2+	USB 2.0 data	2	D2+	6
12	18	D2-	USB 2.0 data		D2-	4
13	16	DRAIN	Ground for Shield Drain		S-GND	10
14	14	SSTX2+	SuperSpeed transmitter
15	12	SSTX2-	SuperSpeed transmitter
16	10	GND	Ground for Power		GND	8
17	8	SSRX2+	SuperSpeed recevier
18	6	SSRX2-	SuperSpeed recevier
19	4	VBUS	+5V Power		+5V	2
20	2	No Pin	Space of Filled Keying		No Pin	9

The standard USB 2.0 Header is missing pin 9 (for keying), but logically pin 9 is for port1's Sheild GND. The sheild is left unconnected if a single port cable is plugged in to port 1. Dual Port hear connectors, share port 10 for both sheilds

This is the most common USB 2.0 header (10 pin [2x5], missing pin 9) and it is pin compatable with the rare 8 pin [2x4] version (missing pins 9 and 10) and 10 pin [2x5] (no pins missing). It is not pin compatable with the very rare (10 pin [2x5], missing pins 10 and 2).

A new feature of USB 3.0 is the SuperSpeed bus, which provides a fourth transfer mode at 5.0 Gbit/s, this is simply left out of the 2.0 header.