CAP1114 datasheet(27/102 Pages) MICROCHIP

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Multiple Channel Capacitive Touch Sensor and LED Driver

Datasheet

SMSC CAP1114

Revision 1.1 (02-04-11)

DATASHEET

5.4.8

RF Noise Detection

Each sensor also contains an integrated RF noise detector. This block will detect injected RF noise on

the CS pin. The detector threshold is dependent upon the noise frequency. If RF noise is detected on

a CS line, that sample is removed and not compared against the threshold.

5.5

Grouped Sensor Behavior

The CAP1114 Grouped sensors (CS8 - CS14) can be configured to function as a single entity that

operates differently than the individual button sensors (for ungrouped behavior see Section 5.6). When

configured as a group these sensors function as a slider and offer three different interface functions

associated with it. These functions are Tap, Press and Hold, or a Slide.

For purposes of a Tap or Press and Hold event, the “DOWN” side of the Grouped sensors are defined

as CS8, CS9 and CS10. The “UP” side of the Grouped Sensors are defined as CS12, CS13, and

CS14. CS11 is neither “UP” nor “DOWN” and a tap or press and hold event on CS11 will not cause

either UP or DOWN status bits to be set.

For purposes of a slide, the “DOWN” direction is decreasing in CS channel number. Conversely, the

“UP” direction is increasing in CS number.

APPLICATION NOTE: The Grouped Sensors will cause either the UP or DOWN status bits to be set but not both

at the same time. In the case that a sensor on both the “UP” side of the slider and the

“DOWN” side of the slider are touched simultaneously, neither the UP nor DOWN status bits

will be set.

5.5.1

Tap

If a touch on any Grouped sensor is detected and held for less than or equal to the M_PRESS bit

settings (default 245ms), a group press is detected, the TAP bit is set, and an interrupt is generated.

Furthermore, the relative position on the slider is determined and the appropriate UP or DOWN status

bits are set and the appropriate LED is actuated.

No further action is taken. If a slide is subsequently detected, the TAP status bit is cleared.

5.5.2

Press and Hold

If a touch on any Grouped sensor is held for longer than the M_PRESS bit settings (default 245ms),

a Group Touch is detected and an interrupt is generated. Furthermore, the relative position on the

slider is determined and the appropriate UP or DOWN status bits are set, the PH bit is set, and the

appropriate LED is actuated.

So long as the Grouped sensor is held, it will flag an interrupt at the programmed repeat rate (as

determined by the RPT_RATE_PH bit settings) indefinitely. Once the touch has been removed, the

Group is returned to its normal operating condition.

The M_PRESS setting is important to distinguish between Tap, Press & Hold and Sliding. If M_PRESS

is set too low, a Press & Hold may be detected during a slow slide. This will cause user confusion as

the Slide direction and LED may change. Longer M_PRESS settings will ensure that the 3 Group

behaviors are reliably distinct and will add more delay prior to the Press & Hold repeat interrupt

generation.

5.5.3

Slider

The Grouped sensors have the capability to detect a slide in either the “UP” or “DOWN” direction as

referenced by the sensor numbers that are used. For example, an “Up” direction slide would be

detected if CS8 detected a touch, followed by CS9, then by CS10, etc. Likewise, a “Down” direction

slide would be detected if CS10 detected a touch, followed by CS9, then by CS8, etc.

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