Problems
A common problem of pointing sticks is the inability to identify the zero position (the position indicating no user touch). A typical solution, which reflects the fact that user operation of the pointing stick is rarely constant, is to interpret any absence of change of pressure (over a given interval, perhaps one or several seconds) as meaning the user has released the stick.
If the user applies exactly constant pressure to the stick for such an interval, this method mistakenly re-zeroes the stick. Then additional pressure is required to achieve the same movement of the screen cursor, and the cursor spontaneously moves in the opposite direction when the user releases the stick. If the user avoids touching the stick, the error ends when the stick detects the real zero position.
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