CAP1114 datasheet(65/102 Pages) MICROCHIP

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Multiple Channel Capacitive Touch Sensor and LED Driver

Datasheet

SMSC CAP1114

Revision 1.1 (02-04-11)

DATASHEET

capacitance associated with a touch. If the sensor input change exceeds the threshold settings, a

touch is detected.

When the BUT_LD_TH bit is set (see Section 6.27 - bit 7), writing data to the Sensor 1 Threshold

When the GP_LD_TH bit is set (see Section 6.27 - bit 6), writing data to the Sensor 1 Threshold

Individual button registers may be updated independently of the Sensor 1 Threshold settings. Similarly,

the Up and Down Threshold registers may be updated independently of the Group Threshold register.

6.29

Button Noise Threshold Registers

The Button Noise Threshold Registers control the value of a secondary internal threshold to detect

noise and improve the automatic recalibration routine. If a Capacitive Touch Sensor output exceeds

the Button Noise Threshold but does not exceed the sensor threshold, it is determined to be caused

by a noise spike. That sample is not used by the automatic re-calibration routine.

The Button Noise Threshold is proportional to the programmed threshold as shown in Table 6.42.

6.29.1

Button Noise Threshold 1 Register

The Button Noise Threshold 1 Register controls the noise threshold for Capacitive Touch Sensors 1-4.

Bits 7-6 - CH4_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 4.

Bits 5-4 - CH3_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 3.

Bits 3-2 - CH2_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 2.

Bits 1-0 - CH1_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 1.

Table 6.41 Button Noise Threshold Registers

ADDR

R/W

DEFAULT

38h

R/W

Button Noise

Threshold 1

CS4_BN_TH

[1:0]

CS3_BN_TH

[1:0]

CS2_BN_TH

[1:0]

CS1_BN_TH

[1:0]

AAh

39h

R/W

Button Noise

Threshold 2

GR_BN_TH

[1:0]

CS7_BN_TH

[1:0]

CS6_BN_TH

[1:0]

CS5_BN_TH

[1:0]

AAh

Table 6.42 CSx_BN_TH Bit Decode

CSX_BN_TH[1:0]

THRESHOLD DIVIDE SETTING

6.25%

12.5%

25% (default)

50%

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