UNIVERSAL SERIAL BUS ( USB ) FUNDAMENTALS

The weirdo trident symbol above is the USB standardization mark and found on all USB devices. Thousands of new USB compliant devices are coming into market ranging from Mouse, Keyboard, Scanner, Printers, Modem, Video Capture Devices, Gaming Consoles...the list is limitless.  I am not the technical / electronics engineer so I will not give in-depth details of this port but I will try my best to explain in simple language about the fundamentals of the USB as I learned.  I do not have any arguments with different opinions on this subject as the information may not be completely reliable on this page.  :-)

USB: Fundamentals & FAQ

So let's go to understand what USB is, at these creators sites.

• USB Technical info  can be found at the best official place by creators of USB.  Dear experts! Immediately go to this site and don't read further on this page. Novice users may stay on and keep reading.
• USB FAQ General, a general FAQ site by the creators of USB
• USB FAQ Developers  by the creators of USB
• USB FAQ by INTEL, a cool site for Developers and advanced users by INTEL itself.
• USB Documention Site, a great page by INTEL itself

USB:  A dream come true. Everyone wanted one IRQ and hundred peripherals

The restrictions of limited number of IRQ in one computer is over now.  Nowadays all motherboards have the USB ports for high-speed 1.5MegaBits/sec to 12MBits/sec in USB ver 1.0 or 1.1 input and output of data to and from the computer.  The improvements are done in newer motherboards to conduct data-transfer upto 480 Megabits/Sec in USB ver 2.0. New motherboards generally come with TWO built-in ports but they use single IRQ channel and single IO memory address.  On single IRQ channel we can use upto 112 USB devices on one computer using USB hubs or USB extension boxes.

There are two types of USB sockets. Type A and Type B.
	Generally the USB sockets are given on CPU with USB-Type-A
	And the USB socket on the peripherals such as Scanner/printers/digital cameras/webcams etc. are of USB Type B

The pinout description and the close-up shot of USB port on CPU Cabinet is given below. Notice the USB logo at top of it.  

The port on motherboard gives the 5volt Output (500mAmp) to power the low voltage peripherals which can be used with computer without extra power supply like USB modems or Floppy Drives.  For my sony vaio laptop, I have an external Floppy Drive and CDROM drive which work only on USB ports and not the extra voltage power.  That's cool.  To know more on USB keep asking those cool silly questions so that I can put them in FAQ for everything else there are following links are enough.

GREAT LINKS ON USB

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FREQUENTLY GIVEN ANSWERS
1.  Any pinout of USB cable to connect two computers directly on USB?
Ans:  NO! It isNOT possible to connect two computers thru USB ports DIRECTLY.  There are some proprietary Cables available in market in less than 60$ which have a built-in electronic circuit with a special software to be installed on both machines. In fact, I am using one such cable to transfer files from my laptop to desktop at high speed, at 12Mbits to 16MBits per second, that's great speed. WARNING: Do not make USB cable on your own as USB ports do have 5volt DC current as output which can damage both motherboards.
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3.  How does the standard USB cable look like?
Ans:  The standard USB cable comes with USB-TYPE-A pin at one end which is connected at motherboard. At other end USB-TYPE-B pin is found which is little smaller and square and connected to the external USB peripherals such as USB modems, Scanners, Printers and thousands of USB devices. Following diagram shows the standard USB cable.

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4. Wouldn't it be possible to just use the transmit and receive of the serial to pins 2 & 3 of the USB cable? I would like to create a small adaptor unit that the palm would sled into and allow access to memory cards.?-Chris Z.
Ans. DON'T EXPERIMENT WITH USB CABLES if you do not know the technical stuff. Even data signals are also produced with some electronic pulses and it can damage the delicate devices like Palms, Laptops or Mobile Phones etc. You must study electronics before you do this else it may result in Hazardous event. Don't say I did not warn you.

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5. Can I connect USB port to Serial port or Parallel port or even at Printer Port directly through cable pinout for data-transfer or any other task?

Ans. NO, Don not try to connect Serial port to USB or Printer port or vice versa. All are different technologies and dont support each other with direct cables or any special pinout cable. There are some devices with special electronics conversion units, but they are convertor units with special electronic cuircuit and driver softwares, and not the direct cables.

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6. I wonder if you could help? I have Intel USB Webcam. I haven't got a spare USB port but have spare PS2 Mouse/Keyboard sockets. I have USB to PS2 adopter. Can I use this method of connection without any damage to motherboard and or Webcam. - Amir a.k.a. Genius(?)

Ans. No.  Technically PS2 and USB 2.0 are different methods. I dont understand that in what way you think that you can attach any USB devices on PS2? Please read and understand USB and PS2 technologies, elsewhere on Internet. I mean that you can not attach any USB devices in PS2 port.  Though some Combo USB Mouse can be attached on PS2 ports. These items are called COMBO input devices. Most Combo devices are designed to connect on USB in Windows Mode and on PS2 in DOS mode in latest motherboards. Except some specially designed combo mouse, No other USB devices can be attached directly to PS2 ports.

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