USB 2.0 is the current USB standard
USB BASICS
Some Basics about the Technology
USB is an extraordinary protocol that acts both as a voltage transfer for powering external devices, and as a low voltage interface for communicating hardware. Because it allows devices to send drivers to the computer, and vice-versa, in an environment of competing products and standards, it has finally made plug-and-play a reality outside of the MAC, rather than an exercise in hair-pulling irony, as I remember it not so fondly.
USB 2.0 is the current USB standard, soon to be replaced, by 3.0, which promises much greener pastures.
The host side USB connector is typically USB A, and is composed of a rectangular metal frame, which operates as the voltage transfer(essentially the electrical plug), and the four metal pins inside, which are embedded into a hard plastic sheath, protected in that way from the rigors of plugging and unplugging devices. The pins send a consistent low-voltage that transmits data between devices.
When a device is plugged into a computer via USB, the computer will query it. The device will then send data to the computer, starting with the drivers of the device. It speaks when spoken to, an architecture known as “Master-Slave.” The ability to transfer driver information from the device is what makes the technology so user friendly. Nothing need be loaded to the computer in advance of connecting a product via USB. If you have a USB connector on your computer, and you have a USB device and cable, you will probably have no trouble with the devices communicating on their own, simply by plugging in.
As mentioned above, the USB architecture also allows for power transfer, a perk that is most commonly displayed in hand-held devices like I-pods, which conveniently recharge when plugged into a computer via USB.
USB has a low power output of 5 volts per outlet, so it is limited in that way to what it can power, but it can power small computer speakers, even lamps…etc., some of which make use of two USB ports to double the power.
USB data transfer is available in 3 different modes…
Interrupt- the DTS polls at intervals for information from devices working under this mode---there is low and high, and the difference is in the latency, the lowest being the more frequent polling.
Bulk- chunks of data are moved, and then corroborated with error screening.
Isochronous- streaming data, errors and drops are not weeded out.- Real-time delivery
Of the total bandwidth allotted to USB functions, 90 percent is available for interrupt and isochronous transfers….the remaining 10 percent, and anything else not being used, is allotted for the bulk transfer function, which is low priority.
USB Pinouts
USB pin-outs vary from the CPU end to the device for different practical reasons. Type A and Type B heads are shaped differently so as to avoid an electrical loop that could be caused by plugging the same cable back into the same computer accidentally.
Micro, 4 pin and 5 pin connectors are small themselves, making them ideal for connecting to hand-held devices.
Here is a link to some useful cables:-
http://www.m2cables.us.com/USB-Cable-Type-A-Male-to-Mini-5-Pin-B-Male-p/m2usb-1520-main.htm
http://www.m2cables.us.com/category-s/372.htm
Here is another link to some useful adapters:-
http://www.m2cables.us.com/USB-Adapters-s/110.htm
The Competition
When does USB rule and when are other options better or more suitable?
The upfront weigh-in on whether to use Firewire, USB, or eSATA, is always the requirement of the device in question, as well as whether or not your computer is currently capable of connecting a particular device. Barring those restrictions, these other details are worth considering.
USB 2.0 may not be the best out there, but it is a cheaper, perfectly suitable technology to meet many needs.
Because of its reasonable price and value for low yield transfer use, its ports are a staple on modern computers and laptops, whereas external eSATA, and Firewire ports are still much rarer. Price and commonality are definitely the strengths of the medium.
USB 3.0
USB 2.0, like every industry heavy-weight, is doomed to retirement some day, and it’s faster little brother will probably start replacing it in new models eventually, because 3.0 is for all early indications, blazingly fast. Tests I watched(notably by the designers of 3.0) showed transfer speeds that were only limited by the hard-drive speeds themselves.
But little brother won’t soon be filling 2.0’s shoes, mostly because 3.0’s “feet” are so unusual. 3.0 is not backwards compatible, it can’t even plug into the same slot. Right now, 3.0 sells with a 2.0 adapter, but that adapter slows 3.0 speeds down to 2.0 levels for the sake of making 3.0 usable in most setups.
What this means is that we are looking at a long road before USB 2.0 is phased out. 2.0 is standard on all Recent PC’s, and devices will continue to be made to those specifications, for at least the next five years.
Conclusion
USB 2.0 is ideal for plug and play devices, such as mice, keyboards, ipods, flash-drives, still-cameras, printers, etc. where more powerful options would be more expensive, and just plain overkill. It starts to show its limitations when dealing with bigger files, and as time goes on those limitations will be more and more on display. In the mean-time, USB 2.0 devices do the job they are meant to do, if more modestly than some of their pricier rivals, and they will find far more computers readily capable of interfacing with them than the competition. 3.0 is here, but even that won’t entirely replace 2.0 for many years, when it is finally standard on office and home computers.
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