Mouse

1
Mouse
TTypes of Mouse   There are three technologies
available to detect the mouse movement, they
are   n      Mechanical n     
Opto-mechanical n      Optical
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Mechanical

• Mechanical This mouse has rollers inside and
  when the mouse is moved the rubber ball
  protruding from the underside of the mouse starts
  to rotate in the direction of the movement. As
  the ball rotates it touches and turns two rollers
  mounted at 90-degree angle to each other. One
  roller is used for back-and-forth (vertical
  movement of mouse) movement and the other roller
  is used for left-right movement (horizontal
  movement of mouse) Each roller is attached to an
  encoder which is like a wheel. As the rollers
  turn, these encoders rotate with them. Two pairs
  of contact bars touch the small metal contact
  points provided on the rims of each of these
  encoders

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Opto-Mechanical Sensors

• Opto-Mechanical Sensors
• The next generation of mouse designs replaced the
  mechanical contacts with an optoisolator
  arrangement (Fig. 8). A hard rubber mouse ball
  still rests against two perpendicularly opposed
  metal actuator rollers, but instead of each
  roller driving an array of contacts, the rollers
  rotate slotted wheels, which are inserted into
  optoisolators. An optoisolator shines LED light
  across an air gap where it is detected by a
  photodiode or phototransistor. When a roller (and
  slotted wheel) spins, the light path between LED
  and detector is alternated or chopped. This
  causes the detectors output signal to oscillate
  thus, pulses are generated. The pulse frequency
  is dependent upon mouse speed. As with the
  mechanical mouse, the opto-mechanical mouse
  produces both positive and negative serial
  pulses, depending on the direction of mouse
  movement.

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Opto-Mechanical Sensors
The opto-mechanical mouse is a great improvement
over the plain mechanical approach. By
eliminating mechanical contacts, wear and tear on
the mouse is significantly reduced, resulting in
much longer life and higher reliability. However,
the mouse is still subject to the interference of
dust and other foreign matter that invariably
finds its way into the mouse housing. Regular
cleaning and internal dusting can prevent or
correct instances of cursor skip or stall. Most
mouse models use opto-mechanical sensors.
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Optical
Optical In this type of mouse, instead of the
ball and rollers, a light source and
photo-detector is used with a special mouse
pad.   When the mouse is moved on the special
pad, light from the light source gets reflected
from the pad and the photo-detectors inside the
mouse detect horizontal and vertical movements
based on the reflected light received. One of
these photo-detectors is used to detect
back-and-forth (vertical movement of mouse)
movement and the other is used for left-right
movement (horizontal movement of mouse).   In
all the above technologies, the depressing of the
mouse buttons produces a signal, which is sent to
the serial port. Depending upon the button and
the number of times the button is pressed, the
software does the task desired by the user.  
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Pin configuration of serial (Mouse) port
Mouse connection A mouse can be connected to the
PC in three ways.   Serial port This is the most
common method of connecting the mouse. One end of
the mouse cord has a nine pin female D-shell
connector that is plugged to the serial port
available at the back of the PC (normally
COM1).   Bus In this type of connection, a
special mouse adapter board is installed in the
PC and the mouse is connected to the adapter.
However, this type of connection uses one slot
and so this method is the least used.   Mouse
port In this type of connection, the mouse
control circuitry is built-in on the motherboard
itself, so there is no wastage of one slot as in
the case of the bus mouse.   Wireless This type
of connection does not use a cable to connect the
mouse to the PC. Instead infrared rays or radio
waves are used to transmit signals from the mouse
to the PC and vice-versa.
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Mouse driver

• Mouse driver 
• The mouse device driver already running in the
  computer (most systems load the mouses device
  driver, such as Microsofts MOUSE.COM, during
  computer initialization) interprets the pulses
  generated by the mouse and translates them into X
  
•  

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Trouble shooting

• The mouse cursor appears, but it only moves
  erratically as the ball moves (if at all)
• Cable Connector This symptom might occur in
  either the horizontal or vertical axis. This
  symptom suggests that an intermittent condition
  is occurring somewhere in the pointing device.
  Check the devices cable connector at the
  computer. Be sure that the connector is tight and
  inserted properly. If the connector does not seem
  to fit tightly in the computer, try a new
  pointing device.
•  
• Dirt More likely, the devices rollers are not
  turning, or are turning only intermittently. In
  most cases, roller stall is caused by a dirty or
  damaged ball, or an accumulation of dirt blocking
  one or both sensors. Clean the ball and blow out
  any dust or debris that might have settled into
  the mouse/trackball housing. Never use harsh
  solvents or chemicals to clean the housings or
  ball.

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Trouble shooting

• IRQ Conflict If one has the mouse connected to a
  standard serial communication port (a COM port),
  one should check that no other devices are using
  the same interrupt (IRQ). For example, COM1 and
  COM3 use the same IRQ, while COM2 and COM4 share
  another IRQ. If one has a mouse on COM1 and a
  modem on COM3, there will almost invariably be a
  hardware conflict. If possible, switch the mouse
  (or conflicting device) to another port and try
  the system again.
•  
• Continuity If no hardware conflict occurs, and
  cleaning does not correct an intermittent
  condition, remove the devices upper housing to
  expose the PC board and use the multimeter to
  check continuity across each wire in the
  connecting cable. If one cannot find continuity
  or repair faulty wiring, simply replace the
  pointing device.

10
Trouble shooting

• One or both buttons function erratically (if at
  all)
• Clean and Check Continuity Buttons are
  prone to problems from dust accumulation and
  general contact corrosion. The first step should
  be power down the computer and disconnect the
  pointing device. Remove the ball and upper
  housing to expose the PC board and switches.
  Spray a small amount of electronics-grade contact
  cleaner into each switch, then work each switch
  to circulate the cleaner. If cleaning does not
  improve intermittent switch contacts, one might
  wish to check continuity across the connecting
  cable.
•  
• The screen cursor appears on the display,
  but it does not move Isolating the fault If the
  cursor appears, the device driver has loaded
  correctly and the application program is
  communicating with the driver. The first step
  should be to suspect the serial connection. If
  there is no serial connection, however, no pulses
  will modify the cursors position. If the device
  is attached correctly to its proper serial port,
  the problem probably exists in the pointing
  devices wiring.
•  

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Trouble shooting

• Continuity Remove the ball and upper housing to
  expose the PC board, then use the multimeter to
  check continuity across each wire in the
  connecting cable. Repair any intermittent or open
  wiring if one can, or simply replace the pointing
  device. 
• The mouse/trackball device driver fails to
  load
• Device Driver The device driver is a short
  program that allows an application program to
  access information from a pointing device. Most
  computer users prefer to load their device
  drivers during system initialization by invoking
  the drivers in the CONFIG.SYS or AUTOEXEC.BAT
  files.
• Improper Connection and Re-Initialization If the
  device driver fails to load during
  initialization, the pointing device might not
  have been detected. Ensure the device is securely
  plugged into the proper serial port (or other
  mouse port). If the device is missing or
  incorrectly inserted, install or re-secure the
  pointing device and allow the system to
  re-initialize.

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Trouble shooting

• Improper path or Corrupted Driver If one
  sees a File not found error message displayed
  at the point the device driver was supposed to
  load, the driver might have been accidentally
  erased, might be corrupted, or might be located
  in a sub-directory where the CONFIG.SYS or
  AUTOEXEC.BAT files are not looking. Try
  re-installing a valid copy of the mouse device
  driver and ensure that the driver is located
  where the calling batch file can access it.
  Reboot the system.  
• No Detection and Error Most well-designed
  application programs check for the presence of a
  pointing device through the device driver during
  initial program execution. If the application
  program aborts or fails to execute because of a
  No mouse found or No mouse driver error,
  return to the preceding paragraphs and recheck
  the device and driver installation. 
• One sees a General protection fault after
  installing a new mouse and driver under Windows