5 and 6 Channel Capacitive Touch Sensor
Datasheet
5.4
Sensor Delta Count Registers
Table 5.5 Sensor Delta Count Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Sensor 1 Delta
Count
10h
11h
12h
13h
14h
15h
R
Sign
64
32
16
8
4
2
1
00h
Sensor 2 Delta
Count
R
R
R
R
R
Sign
Sign
Sign
Sign
Sign
64
64
64
64
64
32
32
32
32
32
16
16
16
16
16
8
8
8
8
8
4
4
4
4
4
2
2
2
2
2
1
1
1
1
1
00h
00h
00h
00h
00h
Sensor 3 Delta
Count
Sensor 4 Delta
Count
Sensor 5 Delta
Count
Sensor 6 Delta
Count
The Sensor 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
capacitor associated with a touch on one of the sensors and is referenced to a calibrated base “Not
touched” count value. The delta is an instantaneous change and is updated once per sensor per
sensing cycle (see Section 4.2.1 - sensor 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 FFh for negative delta counts which may result upon
a release.
5.5
Sensitivity Control Register
Table 5.6 Sensitivity Control Register
ADDR
R/W
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
1Fh
Sensitivity Control
-
DELTA_SENSE[2:0]
BASE_SHIFT[3:0]
2Fh
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. 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 C corresponding to a “lighter” touch. These settings are more
sensitive to noise however and a noisy environment may flag more false touches than higher sensitivity
levels.
APPLICATION NOTE: A value of 128x is the most sensitive setting available. At the most sensitivity settings, the
MSB of the Delta Count register represents 64 out of ~25,000 which corresponds to a touch
of approximately 0.25% of the base capacitance (or a ΔC of 25fF from a 10pF base
capacitance). Conversely a value of 1x is the least sensitive setting available. At these
SMSC CAP1005 / CAP1006
Revision 1.1 (08-05-09)
DATA3S1HEET
SMSC [ SMSC CORPORATION ]
