Stanford Diehl
An individual's taste in pointing devices, like music and art, is highly subjective. Some of us love IBM's TrackPoint device, while some can't quite get the hang of it. Touchpads, too, claim devotees and naysayers, but the technology has made some notable advances over the last few years.
The first widely available touchpad for portables is Alps Electric's (San Jose, CA, (800) 825-2577) GlidePoint (see "Do the Electric Glide," April BYTE, page 203), which uses field-distortion sensing, a capacitance-sensing technology licensed from Cirque (Salt Lake City, UT). The two layers of electrical conductors, arranged in a grid, generate an electrical field over the GlidePoint's surface. Your fingertip distorts the field, and the GlidePoint determines the exact location of your
fingertip by sensing the strength of the distortion at each conductor.
For comparison purposes
, we tried the Cirque technology on a Sharp PC-8900 that comes standard with a GlidePoint. It takes some getting used to, especially the tapping motions required to trigger mouse-clicks, double-clicks, and click and drag. But once you get a feel for it, the GlidePoint is a natural way to navigate a cursor around the screen. You run into trouble, however, when you're dragging an item and your finger runs into the edge of the pad. With the GlidePoint driver, you can configure the right mouse button to act as a drag-lock key, but that's not the best solution.
An even better answer is the Synaptics (San Jose, CA, (408) 434-0110) TouchPad. The TouchPad also takes advantage of capacitance-sensing technology, but the company has extended the pad's capabilities with proprietary algorithms for pattern recognition and adaptive analog VLSI technology. Not only does the TouchPad sense motion of
any kind, it also senses pressure or even the distance of your fingertip from the pad's surface. Although not yet enabled through the current driver, this technology will support pressure-based functions such as handwriting, painting, and other applications that usually require a pressure-sensitive graphics tablet.
To deal with the limitations of dragging, the TouchPad supports Edge Motion. When your finger reaches the edge of the pad's surface, the cursor continues to move in the indicated direction as you apply pressure to the edge of the pad. We used the Synaptics TouchPad on an Epson ActionNote (Torrance, CA, (800) 374-7300), and everything worked as advertised. Edge Motion removed one of the last major complaints about using touchpad technology and made the TouchPad a better choice than the GlidePoint. Your choice of pointing devices is still a personal decision, but touchpad technology just keeps getting better.
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The Synaptics TouchPad (left) and the Alps GlidePoint.
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