Method and apparatus for interfacing computer light pens

Details Method and apparatus for interfacing computer light pens Method and apparatus for interfacing computer light pens

1989-11-09

1993-01-12

Oberley, Alvin E.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

340708, G09G 302

Patent

active

051793687

ABSTRACT:
A method and apparatus to improve the accuracy and responsiveness of computer light pens, while simultaneously reducing the associated computing overhead, is disclosed. A light pen is a device that generates an electrical signal when touched to an illuminated section of a computer screen. The position of the pen on the screen can be determined by timing relationships between the signal from the pen and the synchronizing signals being sent to the screen by its controller. The interface apparatus utilizes a pair of synchronous digital counters, one for each axis, to accumulate the timing information. A special processing method is used for the data that is read from the counters to substantially reduce the false horizontal movement normally associated with light pens. The special processing eliminates the need for frame-to-frame averaging, resulting in greatly improved responsiveness. The improved interface method and apparatus utilize a combination of hardware and software interrupts to reduce computational overhead.

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User's Guide for PXL-350 Hi-Res Light Pen Board, FTG Data Systems, 10801 Dale Street, P.O. Box 615, Stanton, Calif., Apr. 30, 1986.

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