USB (Universal Serial Bus)

What is USB?

• Universal Serial Bus (USB) is a serial bus standard to interface devices to a host computer

• It was designed to allow many peripherals to be connected using a single standardized interface socket

and to improve the Plug and play capabilities by allowing hot swapping or hot plugging

Why?• Ease of adding peripherals to PC

• Low cost, supporting transfer rates of up to 480 Mbps

• Support for many configurations of OS and PC’s

• Standard interface for peripherals in general

• Plug and Play technology

• No need for external power

Overview

• Multiple peripheral devices connected in a tiered-star topology up to 5 levels

• Up to 127 devices, including the hub device

• USB 1.0, 1.1 and 2.0 use a "speak-when-spoken-to“ protocol

• Offers limited power

How was it created?

• USB was developed by a consortium of large companies, such as:

- Microsoft;- IBM; - Apple;- Hewlett-Packard;- NEC; - Intel;- Compaq;- Digital;- Northern Telecom;- Philips;- ...

• Obviously it was very difficult for these companies enter into agreement

• Intel - UHCI - Universal Host Controller Interface (transfer part of the protocol processing for the software (driver), simplifying the electronic controller)

• Compaq, Microsoft, National Semiconductor – OHCI - Open Host Controller Interface (transfer most of the effort to the electronic controller, simplifying the driver software (driver))

• 2.0 – EHCI - Enhanced Host Controller Interface (combines quality of the two models with a greater bandwidth)

Curiosity about the consortium

Device Classes• USB defines class codes used to identify a device’s functionality

and to load a device driver based on that functionalityClass Usage Description Examples

00h Device Unspecifiedclass 0 (Device class is unspecified. Interface descriptors are used for determining the required drivers.)

01h Interface Audio Speaker, microphone, sound card02h Both Communications and CDC Control Ethernet adapter, modem, serial port adapter03h Interface Human Interface Device (HID) Keyboard, mouse, joystick05h Interface Physical Interface Device (PID) Force feedback joystick

06h Interface Image Digital camera (Most cameras function as Mass Storage for direct access to storage media).

07h Interface Printer Laser printer, Inkjet printer

08h Interface Mass Storage USB flash drive, memory card reader, digital audio player, external drives

09h Device USB hub Full speed hub, hi-speed hub

0Ah Interface CDC-Data (This class is used together with class 02h - Communications and CDC Control.)

0Bh Interface Smart Card USB smart card reader0Dh Interface Content Security -0Eh Interface Video Webcam0Fh Interface Personal Healthcare -DCh Both Diagnostic Device USB compliance testing deviceE0h Interface Wireless Controller Wi-Fi adapter, Bluetooth adapterEFh Both Miscellaneous ActiveSync deviceFEh Interface Application Specific IrDA BridgeFFh Both Vendor Specific (This class code indicates that the device needs vendor specific drivers.)

USB Connectors

Cable• The maximum length of a standard USB cable is 3.0 meters (1.1)

or 5.0 meters (2.0)

• Maximum hubs connected in series is 5

• Maximum distance of 30 meters between host and device

- because of the delay

• The data cables are a Twisted pair to reduce noise and crosstalk

Pin Name Cable color Description1 VCC Red +5V2 D− White Data −3 D+ Green Data +4 GND Black Ground

Miniplug/Microplug

Pin Name Color Description

1 VCC Red +5 V

2 D− White Data −

3 D+ Green Data +

4 ID none

permits distinction of Micro-A- and Micro-B-PlugType A: connected to GroundType B: not connected

5 GND Black Signal Ground

USB Versions

• USB 0.7: Released in November 1994

• USB 0.8: Released in December 1994

• USB 0.9: Released in April 1995

• USB 0.99: Released in August 1995

• USB 1.0: Released in January 1996, with data transfer rates of 1.5 Mbit / s

• USB 1.1: Released in 1998

• USB 2.0: Released in April 2000

USB 1.1

• Specified data rates of 1.5 Mbit/s (Low-Speed) and 12 Mbit/s (Full-Speed)

• Standard interface

• Fixed problems identified in 1.0, mostly relating to hubs

• Used for small peripherals

USB 2.0

• Added higher maximum speed of 480 Mbit/s (now called Hi-Speed)

• Uses the same standart connector

• Compatible with 1.1 devices but with reduced speed

• Manufacturers could adopt the standard into their products without the obligation to pay a license to use the technology

• There was an increase in the range of possibilities because of the hi-speed

USB 3.0

• A SuperSpeed rate of 5.0 Gbit/s, 10 times faster than 2.0

• Products using the 3.0 specification are likely to arrive in 2009 or 2010

• The trade name will be SuperSpeed USB

• The technology is similar to PCI Express 2.0 (5-Gbit/s)

- comparing the cables

Applications and Utilities

hugo.baldioti@engenharia.ufjf.br