Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
Most mouse and related products use a slow (typically 1200 Bauds) serial data stream. It connects either directly through a UART or through a HID USB interface.
The mouse sends data to signal it has moved a certain units of distance in the X or Y plane and the display device has to scale the units if necessary then add the offset to the cursor position so it shows movement on the screen.
The easiest way to learn is to dismantle a mouse and look inside.
There are two basic types, ones with a roller ball that rotates one or both slotted wheels at 90 degree angles to each other and ones that sense the visible image beneath them.
In the ball type, the distance and direction is worked out from the number of 'strobes' from the sensors as the slots break or allow the light beams. They are essentially quadrature encoders so distance and direction can be determined easily. The optical mouse uses a simple camera technique to look at the surface beneath it. They assume the surface is stationary so if the picture appears to move, it means the mouse has been moved in the opposite direction.
When the movement has been reported back to the display device, it adds or subtracts from the last stored cursor coordinates and re-draws it in the new location.
Mouse is a simple hardware that measures movement in the x and y directions. These two directions are based on the orientation of the mouse device. Mouse sends the displacements along the x and y directions on a periodic basic.
There is a software driver (mouse) that takes the readings and computes the accel and sends the positions in terms of the screen.
The application software displays the cursor and acts on the mouse commands (as given by the mouse driver).
In post #4, the basic operating principle of a mouse with roller ball has been explained. That provides a resolution of about 600dpi but optical mouse can give a better resolution.
The mouse communicates (the older ones) using a serial port (I think at about 1200 baud) and that determines the data update rate. It is not really very fast (from a computer's angle) but it is fast from a mechanical point of view.
Accuracy is not critical because the software puts the cursor where it is expected to be.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
