PENny: An Extremely Low-Cost Pressure-Sensitive Stylus for Existing Capacitive Touchscreens.

By building a wired passive stylus we have added pressure sensitivity to existing capacitive touch screen devices for less than $10 in materials, about 1/10th the cost of existing solutions. The stylus makes use of the built-in audio interface that is available on most smartphones and tablets on the market today. Limitations of the device include the physical constraint of wires, the occupation of one audio input and output channel, and increased latency equal to the period of at least one audio buffer duration. The stylus has been demonstrated in two NIME applications thus far: a visual musical score drawing and a singing synthesis application.