CAP1208 datasheet(50/67 Pages) MICROCHIP

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8-Channel Capacitive Touch Sensor

Datasheet

DS00001570B-page 50

 2014 Microchip Technology Inc.

The Sensor Input Threshold registers store the delta threshold that is used to determine if a touch has

been detected. When a touch occurs, the input signal of the corresponding sensor pad changes due

to the 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 5.18 - bit 7), writing data to the Sensor Input 1 Threshold

5.20

Sensor Input Noise Threshold Register

The Sensor Input Noise Threshold register controls the value of a secondary internal threshold to

detect noise and improve the automatic recalibration routine. If a capacitive touch sensor input exceeds

the Sensor Input Noise Threshold but does not exceed the sensor input threshold, it is determined to

be caused by a noise spike. That sample is not used by the automatic recalibration routine. This

feature can be disabled by setting the DIS_DIG_NOISE bit.

Bits 1-0 - CS1_BN_TH[1:0] - Controls the noise threshold for all capacitive touch sensor inputs, as

shown in Table 5.34. The threshold is proportional to the threshold setting.

36h

R/W

Sensor Input 7

Threshold

-64

40h

37h

R/W

Sensor Input 8

Threshold

-64

40h

Table 5.33 Sensor Input Noise Threshold Register

ADDR

R/W

DEFAULT

38h

R/W

Sensor Input

Noise Threshold

CS_BN_TH

[1:0]

01h

Table 5.34 CSx_BN_TH Bit Decode

CS_BN_TH[1:0]

PERCENT THRESHOLD SETTING

25%

37.5% (default)

50%

62.5%

Table 5.32 Sensor Input Threshold Registers (continued)

ADDR

R/W

DEFAULT

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