A Cost-Effective Three-In-One PDA Input Control

We attach an inexpensive pressure sensor to the side of a PDA and use it as three input devices at once. Users can squeeze the device to provide near-continuous input to applications. At the same time the drivers interpret a sudden full squeeze as the push of a virtual button. A user's sudden pressure release while squeezing is detected as the push of a second virtual button. We briefly describe our hardware and signal processing techniques. The remainder of the writing describes an experiment that explores whether users can cope cognitively with the 3-in-1 control. We compare against a three-control setup consisting of a jog wheel and two physical buttons. We show that the 3-in-1 control enables a 13% faster reaction time over the three-control, but that the 3-in-1 suffers a 4% penalty in the accuracy of users choosing between the two buttons in response to cues from an application. We show that a good choice of application cue is more important for assuring accuracy in the 3-in-1 than in the more traditional set of separate controls. In particular, we examined four types of cues. One abstract cue, one cue with clear semantic relevance to the application, one symbolic, and one textual cue.