3 Channel Capacitive Touch Sensor with 3 LED Drivers
Datasheet
Note 5.1 Recalibration Samples refers to the number of samples that are measured and averaged
before the Base Count is updated however does not control the base count update period.
Note 5.2 Update Time refers to the amount of time (in polling cycle periods) that elapses before the
Base Count is updated. The time will depend upon the number of channels active, the
averaging setting, and the programmed cycle time.
5.18
Sensor Input Threshold Registers
Table 5.32 Sensor Input Threshold Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Sensor Input 1
Threshold
30h
31h
32h
R/W
-
64
32
16
8
4
2
1
40h
Sensor Input 2
Threshold
R/W
R/W
-
-
64
64
32
32
16
16
8
8
4
4
2
2
1
1
40h
40h
Sensor Input 3
Threshold
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 5.17 - bit 7), writing data to the Sensor Input 1 Threshold
register will update all of the sensor input threshold registers (31h - 32h inclusive).
5.19
Sensor Input Noise Threshold Register
Table 5.33 Sensor Input Noise Threshold Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Sensor Input
Noise Threshold
CS_BN_TH
[1:0]
38h
R/W
01h
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 re-calibration 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.
SMSC CAP1133
Revision 1.32 (01-05-12)
DATA4S3HEET
SMSC [ SMSC CORPORATION ]
