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RRFCTM (Reversing Ramped Field Capacitive) Touch Technology

Wacom's patent-pending RRFC touch technology employs newly designed low-power circuitry and revolutionary reversing ramped electro-static fields to deliver pinpoint precision and drift-free performance to touchscreen users. The technology can be integrated into dual-input applications with Wacom's market-leading EMR pen-input technology or in applications with touch-only interfaces. This incredible flexibility provides OEM partners access to best-in-class human interface solutions to meet their application or device requirements.

Principles of Wacom RRFC Touch

Wacom RRFC touch uses a similar glass sensor (touchscreen) construction to existing capacitive touch solutions but detects and measures the touch using a completely new technique based on mostly digital circuitry and proven Wacom EMR pen ASIC components. Touch location is detected by measuring the very small current changes that result from the close proximity of a finger to four ramped electro-static fields generated over the surface of the sensor (as opposed to a single flat electro-static field used by legacy capacitive solutions). This proprietary method of driving the sensor and of processing the changes in current yield significant performance advantages to any other capacitive touch solution available today.

RRFC touch starts by generating an AC voltage which is applied to two adjacent corners and a DC voltage which is applied to the opposite two corners forming a voltage ramp across the sensor and a corresponding ramped electro-static field. The controller repeats this for all four possible corner combinations.. The measurement of the energy in the fields happens at each corner in a way that efficiently removes all capacitance effects except those that are related to a finger touch. In its simplest form, the actual touch point on the X or Y axis is a ratio of the measured results from the two ramped fields that were generated on that axis.

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Conceptual drawing showing the four "reversing" ramped electro-static fields

The remaining signal data representing the touch is then passed through a highly-efficient set of filters embedded in the same ASIC used for Wacom's market-leading EMR pen technology and then converted to digital data for processing. The 90% digital operation and proprietary algorithms for touch point calculation compensate for factors such as changing grounding conditions, noise in the environment and ultra-low signals that cause jitter or drift.

Because Wacom uses the same ASIC electronics for its RRFC touch as for its market-leading EMR pen technology, cost is also very advantageous and pricing can be comparable to existing surface capacitive products. These electronics maintain the speed and sensitivity expectations that the market already has for capacitive touch in AC-powered applications and extend capacitive touch technology into a market that was previously out-of-reach: battery-operated devices such as Tablet PCs.

Wacom Advantages

Wacom RRFC touch provides a solution to many disadvantages of today's surface capacitive technology.

Battery operation and floating ground

Wacom RRFC touch is proven to work effectively on Tablet PCs. Wacom RRFC touch has shown that it is possible to get the benefits of capacitive technology on a battery-operated platform with a touch response that is fast, sensitive and accurate even if the user is not grounded, is not touching the Tablet PC casing, or in cases when the Tablet PC casing is electrically isolated. Moreover, when moving around with a Tablet PC, or when switching between battery and AC power sources, calibration remains stable.

Drift-free

By using common analog circuitry for all corners and constantly monitoring the environment and its own performance, Wacom RRFC touch compensates for all factors that create apparent drift. Calibrations should only be needed once during the lifetime of a well-engineered design.

Linear to the edge

Wacom RRFC uses sophisticated border designs that result in high accuracy right up to the edge of the active area. The specification for accuracy in Wacom RRFC touch will be ± 2mm even at the edge of the glass.

Immune to noise

With the reversing fields technique and by sharing the ASIC technology used in Wacom's market-leading EMR pen technology, noise is reduced to a minimum. The resulting signal-to-noise ratio is so good that, under certain conditions, Wacom RRFC can recognize the lightest of touches.

Integration with Wacom's market-leading EMR pen technology

For Tablet PC OEMs designing dual-input applications, Wacom RRFC touch technology can be easily integrated with Wacom's market-leading EMR pen-input technology. Wacom RRFC touch uses the same mass-produced ASIC and MCU electronics architecture as its market-leading EMR pen input technology. Both pen and touch input are driven from the same ASIC/MCU pair, thereby reducing cost while assuring superior optical performance. OEMs will have little additional cost, other than the difference between the sensor glass and the current LCD protection panel, in order to add this exciting new technology to any device that uses Wacom EMR pen technology today.