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Publisher20.2 Mouse Characteristics
Here
are the important characteristics of mice and trackballs:
Mice are available that use the following mechanisms:
Mechanical mice use a rubber-coated ball that contacts the mouse pad.
Moving the mouse causes the ball to move, which in turn causes one or
both of the internal cylindrical rollers with which the ball is in
contact to move. These two internal rollers are oriented at
90° to each other, which allows one to respond to
horizontal mouse movement and the other to vertical mouse movement.
Connected to the end of each roller is a wheel with many small
notches around its circumference. As the wheel rotates, these notches
alternately pass or block light from an LED aimed to impinge on a
sensor. The rate at and duration for which the sensors see the light
flickering correspond to how fast, how far, and in what direction the
ball is moving.Modern mechanical mice are inexpensive and reliable, but require
frequent cleaning. The improvements in second-generation optical
mice, described next, have largely relegated mechanical mice to
bargain-basement systems.
Early
mechanical mice provided limited resolution, were relatively
unreliable, and required very frequent cleaning. Manufacturers
addressed these problems by introducing optical mice, which
substituted an optical sensor for the mouse ball. Reducing the number
of moving parts increased reliability, and because the optical mouse
was a sealed unit, cleaning was needed much less often. But
first-generation optical mice had two drawbacks. First, their
relatively primitive sensors required a special mouse pad that
contained an embedded mesh of very fine wires and was easily damaged.
Second, they were much more expensive than mechanical mice. As
mechanical mice continued to improve, optical mice gradually became
niche products and disappeared from the market for several years.A few years
ago, Microsoft introduced second-generation optical mice that use
enhanced sensors and more powerful laser diodes, which Microsoft
calls IntelliEye technology. We call them red-eye mice. Because they
are more sensitive and use a brighter light source, these mice can
detect very minor variations in surface texture. That allows them to
work on nearly any surface from a standard mouse pad to a bare
desktop. In fact, they work on everything we've
tried except a mirror. We've even used them
successfully on featureless beige computer cases and unmarked sheets
of white paper. Because they are sealed units, they do not require
routine cleaning, which is a blessing for people who eat, drink, or
smoke at their desks.
At first, IntelliEye mice were much more expensive than mechanical
mice, but that price premium nearly disappeared as other
manufacturers began shipping similar models. Basic red-eye mice now
sell for $15, which has killed the market for mechanical mice. We now
use only red-eye mice, and recommend them exclusively.
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At least one type of mouse doesn't require any
mousing surface at all. Gyration's Ultra Cordless
Optical Mouse can be used as a standard optical mouse when there is a
mousing surface available. If there isn't, you can
enable gyroscopic mode (at a substantial penalty in battery life) and
simply wave the mouse around in midair. The built-in gyroscopes
detect the mouse movements and translate them into pointer movements
on screen. This capability doesn't come cheaply. A
basic model with a 25-foot range sells for $70 or so, and models with
longer ranges cost correspondingly more.
Unlike the Macintosh world, where one-button mice are the rule, PC
mice typically have two buttons, and some have three or more. In
addition, many mice have a scroll wheel, which can function as
another button. Using anything beyond the standard two buttons
requires that both the driver and the application support the
additional buttons. For example, the extended functions of the
Microsoft Wheel Mouse are available only in applications that are
specifically written to implement those extended functions, and only
then if the enhanced mouse driver is installed to replace the
standard mouse driver.
Mice
have been produced in four interfaces. In relative order of current
popularity, these interfaces include:
The
PS/2 mouse uses the same mini-DIN physical
connector as the PS/2 keyboard, and interfaces to the PC using a
second msi8042. But the mouse port uses IRQ12versus IRQ1 for
the keyboard portwhich means that the mouse port and keyboard
port are not interchangeable. All ATX motherboards provide a PS/2
mouse port on the I/O panel. Late model AT and Baby AT motherboards
provide a PS/2 mouse port in the form of header pins on the
motherboard, and use a port extender cable to jumper the header pins
to a port connector on the back panel. The arrangement and pinouts of
that header-pin connector are not standard. We have seen motherboards
that use five-pin inline connectors, six-pin inline connectors, and
2x3 rectangular connectors. Even motherboards that use the same
physical connector may use different pinouts. Most AT motherboards
include a matching port extender. If yours does not, verify the
pinouts in the motherboard manual before purchasing an extender.
A USB mouse uses no special resources beyond
those claimed by the USB host controller itself. Unlike USB
keyboards, USB mice do not require BIOS support because they need not
be accessible until the operating system has loaded. They do require
an operating system, such as Windows 9X/2000/XP or Linux, that
supports USB. Many current mice offer the USB interface, and usually
include an adapter to allow the mouse to be connected to a standard
PS/2 mouse port.
Most AT and Baby AT motherboards from 1995 and earlier do not include
a PS/2 mouse connector. With these systems, you normally use a
serial mouse. A serial mouse uses a standard
DB9F connector, and connects to a DB9M serial port connector on the
PC. A serial mouse uses no special resources other than the standard
serial port resources for the port to which it is connected (IRQ4 and
base address 03F8-03FF for COM1, or IRQ3 and 02F8-02FF for COM2). You
can connect a serial mouse to either serial port. When the mouse
driver initializes, it detects which port the mouse is connected to
and uses the appropriate IRQ and base address to access it. Serial
mice are obsolete, although many remain in service on older systems.
A bus
mouse (also called an InPort mouse)
is so named because it connects to an adapter that plugs into the
expansion bus. Bus mice were introduced to allow connecting a mouse
to a PC that had no free serial ports. The adapter card is an 8-bit
ISA card that provides selectable IRQ (usually 2, 3, 4, or 5) and
base address settings. However, as an 8-bit card, it is limited to
using 8-bit IRQs, most or all of which are already in use on a PC
with two active serial ports, which is the reason for using a bus
mouse in the first place. Ordinarily, the only available choice is
IRQ5. If the system has an 8-bit sound card installed, IRQ5 is also
occupied, which leaves no alternative unless you are willing to
disable the IRQ for LPT1. Bus mice and InPort adapters are obsolete.
