How USB Ports Work

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by Marshall Brain from How Stuff Works

Just about any computer that you buy today comes with one or more Universal Serial Bus connectors on the back. These USB connectors let you attach everything from mice to printers to your computer quickly and easily. The operating system supports USB as well, so the installation of the device drivers is quick and easy, too. Compared to other ways of connecting devices to your computer (including parallel ports, serial ports and special cards that you install inside the computer's case), USB devices are incredibly simple!

In this article, we will look at USB ports from both a user and a technical standpoint. You will learn why the USB system is so flexible and how it is able to support so many devices so easily -- it's truly an amazing system!

Anyone who has been around computers for more than two or three years knows the problem that the Universal Serial Bus is trying to solve -- in the past, connecting devices to computers has been a real headache!

Printers connected to parallel printer ports, and most computers only came with one. Things like Zip drives, which need a high-speed connection into the computer, would use the parallel port as well, often with limited success and not much speed.

Modems used the serial port, but so did some printers and a variety of odd things like Palm Pilots and digital cameras. Most computers have at most two serial ports, and they are very slow in most cases.

Devices that needed faster connections came with their own cards, which had to fit in a card slot inside the computer's case. Unfortunately, the number of card slots is limited and you needed a Ph.D. to install the software for some of the cards. The goal of USB is to end all of these headaches. The Universal Serial Bus gives you a single, standardized, easy-to-use way to connect up to 127 devices to a computer.

Just about every peripheral made now comes in a USB version. A sample list of USB devices that you can buy today includes:

Printers
Scanners
Mice
Joysticks
Flight yokes
Digital cameras
Webcams
Scientific data acquisition devices
Modems
Speakers
Telephones
Video phones
Storage devices such as Zip drives
Network connections

USB cables and connectors that allow your computer to communicate with these devices.

USB Cables and Connectors
Connecting a USB device to a computer is simple -- you find the USB connector on the back of your machine and plug the USB connector into it.

If it is a new device, the operating system auto-detects it and asks for the driver disk. If the device has already been installed, the computer activates it and starts talking to it. USB devices can be connected and disconnected at any time.

Many USB devices come with their own built-in cable, and the cable has an "A" connection on it. If not, then the device has a socket on it that accepts a USB "B" connector.

The USB standard uses "A" and "B" connectors to avoid confusion:

"A" connectors head "upstream" toward the computer.
"B" connectors head "downstream" and connect to individual devices.
By using different connectors on the upstream and downstream end, it is impossible to ever get confused -- if you connect any USB cable's "B" connector into a device, you know that it will work. Similarly, you can plug any "A" connector into any "A" socket and know that it will work.

USB Hubs
Most computers that you buy today come with one or two USB sockets. With so many USB devices on the market today, you easily run out of sockets very quickly. For example, on the computer that I am typing on right now, I have a USB printer, a USB scanner, a USB Webcam and a USB network connection. My computer has only one USB connector on it, so the obvious question is, "How do you hook up all the devices?"

The easy solution to the problem is to buy an inexpensive USB hub. The USB standard supports up to 127 devices, and USB hubs are a part of the standard.

A hub typically has four new ports, but may have many more. You plug the hub into your computer, and then plug your devices (or other hubs) into the hub. By chaining hubs together, you can build up dozens of available USB ports on a single computer.

Hubs can be powered or unpowered. As you will see on the next page, the USB standard allows for devices to draw their power from their USB connection. Obviously, a high-power device like a printer or scanner will have its own power supply, but low-power devices like mice and digital cameras get their power from the bus in order to simplify them. The power (up to 500 milliamps at 5 volts) comes from the computer. If you have lots of self-powered devices (like printers and scanners), then your hub does not need to be powered -- none of the devices connecting to the hub needs additional power, so the computer can handle it. If you have lots of unpowered devices like mice and cameras, you probably need a powered hub. The hub has its own transformer and it supplies power to the bus so that the devices do not overload the computer's supply.

The USB Process
When the host powers up, it queries all of the devices connected to the bus and assigns each one an address. This process is called enumeration -- devices are also enumerated when they connect to the bus. The host also finds out from each device what type of data transfer it wishes to perform:

Interrupt - A device like a mouse or a keyboard, which will be sending very little data, would choose the interrupt mode.

Bulk - A device like a printer, which receives data in one big packet, uses the bulk transfer mode. A block of data is sent to the printer (in 64-byte chunks) and verified to make sure it is correct.

Isochronous - A streaming device (such as speakers) uses the isochronous mode. Data streams between the device and the host in real-time, and there is no error correction.
The host can also send commands or query parameters with control packets.
As devices are enumerated, the host is keeping track of the total bandwidth that all of the isochronous and interrupt devices are requesting. They can consume up to 90 percent of the 480 Mbps of bandwidth that is available. After 90 percent is used up, the host denies access to any other isochronous or interrupt devices. Control packets and packets for bulk transfers use any bandwidth left over (at least 10 percent).

The Universal Serial Bus divides the available bandwidth into frames, and the host controls the frames. Frames contain 1,500 bytes, and a new frame starts every millisecond. During a frame, isochronous and interrupt devices get a slot so they are guaranteed the bandwidth they need. Bulk and control transfers use whatever space is left. The technical links at the end of the article contain lots of detail if you would like to learn more.

USB Features
The Universal Serial Bus has the following features:

The computer acts as the host.

Up to 127 devices can connect to the host, either directly or by way of USB hubs.

Individual USB cables can run as long as 5 meters; with hubs, devices can be up to 30 meters (six cables' worth) away from the host.

With USB 2.,the bus has a maximum data rate of 480 megabits per second.

A USB cable has two wires for power (+5 volts and ground) and a twisted pair of wires to carry the data.

On the power wires, the computer can supply up to 500 milliamps of power at 5 volts.

Low-power devices (such as mice) can draw their power directly from the bus. High-power devices (such as printers) have their own power supplies and draw minimal power from the bus. Hubs can have their own power supplies to provide power to devices connected to the hub.

USB devices are hot-swappable, meaning you can plug them into the bus and unplug them any time.

Many USB devices can be put to sleep by the host computer when the computer enters a power-saving mode.
The devices connected to a USB port rely on the USB cable to carry power and data.

USB 2.0
The standard for USB version 2.0 was released in April 2000 and serves as an upgrade for USB 1.1.

USB 2.0 (High-speed USB) provides additional bandwidth for multimedia and storage applications and has a data transmission speed 40 times faster than USB 1.1. To allow a smooth transition for both consumers and manufacturers, USB 2.0 has full forward and backward compatibility with original USB devices and works with cables and connectors made for original USB, too.

Supporting three speed modes (1.5, 12 and 480 megabits per second), USB 2.0 supports low-bandwidth devices such as keyboards and mice, as well as high-bandwidth ones like high-resolution Webcams, scanners, printers and high-capacity storage systems. The deployment of USB 2.0 has allowed PC industry leaders to forge ahead with the development of next-generation PC peripherals to complement existing high-performance PCs. The transmission speed of USB 2.0 also facilitates the development of next-generation PCs and applications. In addition to improving functionality and encouraging innovation, USB 2.0 increases the productivity of user applications and allows the user to run multiple PC applications at once or several high-performance peripherals simultaneously.

Trustwave Security Alert: Conficker Worm Variant C Expected to Attack on April 1, 2009

We are members of Trustwave. We just received this notice and thought the readers on USB Warm Gadgets would like to know, too....

from Trustwave

As you may have read in various news reports, a variant of the Conficker worm (a computer virus that has been propagating across the Internet) is expected to begin behaving more maliciously on April 1, 2009.


The first variant of the worm was identified in 2008. Once a computer was infected, the worm would contact one or more of 250 URLs to download malicious applications that, among other things, allowed attackers to take control of the infected system or steal confidential data. A number of organizations took action in early 2009 to bar those particular URLs. The new variant of the worm, Conficker C, increases the number of different URLs to 50,000. A review of the worm's code shows that Conficker C will begin contacting those URLs on April 1, 2009.

The worm spreads successfully via un-patched systems, weak passwords or by running automatically when removable media such as a USB drive is attached to a computer.

The best way to prevent infection or the repercussions of infection is to ensure that your systems' patches and anti-virus programs are up-to-date and to disable Windows' AutoRun feature. Visit Microsoft's Malware Protection Center entry about the Conficker worm at http://www.microsoft.com/security/portal/Entry.aspx?Name=Worm:Win32/Conficker.a and click on the Prevention tab for more information.

In addition, it's important to note how Trustwave solutions help protect against the worm:

• Trustwave's Network Access Control (NAC) solution denies network access to un-patched devices and bars access for devices that exhibit malware-like behavior


• Trustwave Unified Threat Management (UTM) service prevents in- and out-bound connections to unknown/illegitimate sources


• TrustKeeper® vulnerability scans discover vulnerabilities that may put network devices at risk


• TrustKeeper Agent monitors a system's security settings to ensure automatic updates are enabled and notifies administrators if they are disabled

For more information about Trustwave solutions, please visit our Web site at https://www.trustwave.com.

Trustwave periodically issues Security Alerts such as this one to inform customers about threats that may affect their efforts to protect sensitive information, secure their network environment and comply with industry standards and other regulations.

Warm gadgets needed for laptop cool base users

Microsoft's new laptop cooler will keep the laptop cool, and your hands, too. Cold hands using the laptop were always kept warm from the heat of a laptop computer. Now, with the heat gone, cold computer hands will be a problem for laptop users. Commonly reported a cold mouse hand and cold keyboard hands are experienced by desk top users. Laptop users relied upon the heat generated from the laptop to keep their digits warm.

The laptop cooler may be a welcomed gadget during the summer, but as soon as the temperatures drop and hands get cold, people will turn to their warm mouse, heated mouse pad and heated keyboard pad for relief.

New laptop cooler
By Stanley A. Miller II of the Journal Sentinel

Microsoft announced two new computer accessories today, a notebook cooling base and its popular Arc Mouse in new colors. The sleek, slim notebook cooling base -- measuring only 1.16 inches thick -- is designed to do just what you'd expect: keep your laptop from getting uncomfortably warm. It does this using a fan and a cooling channel, and the base is contoured to rest firmly on your desk or lap, offering an ergonomically friendly typing angle. It also has a cable management clip, and it's powered via a computer's USB port so no batteries are needed. The base comes in white and black and costs $30.

Blog Catalog - Heated Computer Keyboard

Need warmth for your computer keyboard hands? Wrists? Arms? The ValueRays heated keyboard pad is ergonomically shaped and delivers the right amount of support and heat. Body temperature is about 98.6 degrees farenheit. The ValueRays USB Heated Keyboard Warm Wrist Pad generates a regulated heat ranging from 99 to 104 degrees. The heat the ValueRays USB Heated Keyboard Warm Wrist Pad generates keeps the hands, wrists and arms comfortably warm while working at the keyboard.

Source: http://www.valuerays.com/

Do You Feel Cold When You Shouldn’t? Get a warm computer gadget!

When you are sitting at the computer, and you feel like crawling under the covers . . . slip your cold mouse hand inside the mouse hand warmer blanket. Shop Etsy, eBay & Amazon.

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Do You Feel Cold When You Shouldn’t?
by Vic Shayne, PhD

Most of us can relate to what it’s like to feel cold when we’re sick with the flu. It’s just hard to warm up. You can be sick in the middle of summer and still want to cover yourself in a blanket. But does this happens to you when you don’t have a cold or flu? If it does, you’re not alone.

Maintaining a feeling of comfortable temperature is a balancing act performed by your body with the help of several major factors. Few doctors would disagree that the main regulating feature of the human body is the thyroid gland. People with thyroid problems often experience feelings of internal cold and ofen cold hands a feet.

The thyroid is fed with minerals, and primarily iodine. Iodine is found in sea food such as fish and sea weed. A few decades ago the food industry began adding iodine to table salt. However, table salt is a highly refined substance that may do more harm than good. Unrefined sea salt is the better choice for your kitchen. Overall, though, there are some researchers who are telling us that we are getting nowhere close to enough iodine on a daily basis, and that the RDA numbers are too low to benefit us.

If you’re experiencing constant cold inside your body, there are three recommended supplements to explore before entertaining the idea of iodine:

BFood Complex: supplies the vitamin B and helper foods that create energy in cells

CellPower: supplies foods that produce energy inside the mitochondria of cells

SuperGreens PhytoFood: supplies green foods with minerals, vitamins, amino acids and warming foods.

Infrared heat usb warm computer gadgets

Infrared heat is the healing rays of the sun. Using USB infrared computer devices gives you the healing rays of the sun without the harmful UV rays. USB warm gadgets are good for you. They keep your hands warm while you are working, and at the same time provide deep penetrating healing heat to sore hands and muscles. The infrared heat rays are also detoxifying. The heat removes toxins from the blood stream we pick up in our everyday living through the air and food we eat.

To read more about the healing effects of infrared heat, visit IGMproducts.com or ValueRays.com.

USB Warm Gadgets

Mouse Hand Warmer blanket pouch to hold your favorite heated mouse and warm mouse pad

USB Warm Gadgets blog is about gizmos you can plug into your computer to keep you warm when you're cold. Is your office or computer area cold? Is it drafty? Do you get cold when you are sitting long hours working at the computer? Does your mouse hand get cold? Do your fingers get numb? Maybe you need an USB Warm Computer Gadget. We will gather information about warming computer gadgets and post the information here. If you have a question, please Contact Us. Comments are welcomed. If you'd like to exchange links, please Contact Us!