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

2. 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

3. 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 detector’s 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.

4. 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.

5. 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.

6. 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.

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

8. 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 device’s 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 device’s 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.

9. 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 device’s 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 cursor’s position. If the device is attached correctly to its proper serial port, the problem probably exists in the pointing device’s wiring.

11. 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.

12. 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