CAP1208 datasheet(33/67 Pages) MICROCHIP

33 / 67 page

8-Channel Capacitive Touch Sensor

Datasheet

 2014 Microchip Technology Inc.

DS00001570B-page 33

5.4

Sensor Input Delta Count Registers

The Sensor Input Delta Count registers store the delta count that is compared against the threshold

used to determine if a touch has been detected. The count value represents a change in input due to

the capacitance associated with a touch on one of the sensor inputs and is referenced to a calibrated

base “not touched” count value. The delta is an instantaneous change and is updated once per sensor

input per sensing cycle (see Section 4.3.2, "Sensing Cycle").

The value presented is a standard 2’s complement number. In addition, the value is capped at a value

of 7Fh. A reading of 7Fh indicates that the sensitivity settings are too high and should be adjusted

accordingly (see Section 5.5).

The value is also capped at a negative value of 80h for negative delta counts which may result upon

a release.

5.5

Sensitivity Control Register

The Sensitivity Control register controls the sensitivity of a touch detection.

Bits 6-4 DELTA_SENSE[2:0] - Controls the sensitivity of a touch detection for sensor inputs enabled

in the Active state. The sensitivity settings act to scale the relative delta count value higher or lower

based on the system parameters. A setting of 000b is the most sensitive while a setting of 111b is the

least sensitive. At the more sensitive settings, touches are detected for a smaller delta capacitance

Table 5.5 Sensor Input Delta Count Registers

ADDR

R/W

DEFAULT

10h

Sensor Input 1

Delta Count

Sign

00h

11h

Sensor Input 2

Delta Count

Sign

00h

12h

Sensor Input 3

Delta Count

Sign

00h

13h

Sensor Input 4

Delta Count

Sign

00h

14h

Sensor Input 5

Delta Count

Sign

00h

15h

Sensor Input 6

Delta Count

Sign

00h

16h

Sensor Input 7

Delta Count

Sign

00h

17h

Sensor Input 8

Delta Count

Sign

00h

Table 5.6 Sensitivity Control Register

ADDR

R/W

DEFAULT

1Fh

R/W

Sensitivity Control

DELTA_SENSE[2:0]

BASE_SHIFT[3:0]

2Fh

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