## Input/Output Device Driver Reference

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### Accuracy of the X,Y Report

Touch accuracy (or lack of it) is a primary reason for the need to improve Touch selection. There are many factors that affect Touch accuracy, including:

Style of touch

As the screen is touched, from the point of touch down to lift off, there can be appreciable movement of the reported X,Y position, even though the intent is to keep the contact point stationary. This can depend on the way the screen is touched; for example, a rapid stab at the screen ordinarily produces more variation than a slower, lighter touch.

On-screen touch threshold

Lowering the on-screen touch threshold makes the system not only more sensitive to touch but also to external unwanted noise, such as mechanical vibration.

Filter cut-off frequency

Increasing the system's low pass cut-off frequency can increase the system' s responsiveness to fast touches, but it does so at the expense of not being able to filter out unwanted noise, variation, and movement.