Cursor tracking

Abstract

In a cursor tracking system (FIG. 11), a pointing device includes a plurality of force sensors (304), optionally integrated with a keyswitch on a computer keyboard. The force sensors detect lateral and vertical forces applied to the keycap (300) by a user (302) for cursor control. Raw force data is acquired by A/D apparatus (306) and transmitted (310,312) to a host processor. Driver level software in the host linearizes the raw force values (316, FIG. 12D) to compensate for anomolies and nonlinearities in the force sensors, keyboard mechanics, and A/D. The resulting linear force values are adjusted (320) to compensate for preloading bias forces (318) on the sensors. The unbiased, linear force values and sensor configuration (322) are used to determine a net XY vector (324, FIG. 16). A speed value is determined by a quadratic mapping of the XY vector magnitude (328), taking mouse button status into account. The speed value is scaled by a speed factor, clamped according to a speed limit value, and the result used to determine a total displacement value which, in turn, is used to scale the XY vectors to determine X and Y cursor displacement for repositioning the cursor. The quadratic mapping coefficients, as well as the speed factor and speed limit values, are user-alterable at run time, to allow customizing the response of the cursor tracking system. The result is a low-cost pointing system having excellent responsiveness for ergonomic efficiency. The system is useful in most computer systems, such as IBM AT-compatible systems, to allow pointing operations without use of a separate pointing device such as a mouse.