5 and 6 Channel Capacitive Touch Sensor
Datasheet
The Sensor 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 changes due to the
capacitance associated with a touch. If the sensor input change exceeds the threshold settings, then
a touch is detected.
When the BUT_LD_TH bit is set (see Section 5.15 - bit 7), writing data to the Sensor 1 Threshold
register will update all of the sensor threshold registers (31h - 37h inclusive).
5.17 Sensor Noise Threshold Registers
Table 5.27 Sensor Noise Threshold Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Sensor Noise
Threshold 1
CS4_BN_TH
[1:0]
CS3_BN_TH
[1:0]
CS2_BN_TH
[1:0]
CS1_BN_TH
[1:0]
38h
R/W
55h
Sensor Noise
Threshold 2
CS6_BN_TH
[1:0]
CS5_BN_TH
[1:0]
39h
R/W
0
1
0
1
55h
The Sensor 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 Sensor Noise Threshold but does not exceed the sensor threshold, then it is determined to be
caused by a noise spike. That sample is not used by the automatic re-calibration routine.
The Sensor Noise Threshold is proportional to the programmed threshold as shown in Table 5.28.
Table 5.28 CSx_BN_TH Bit Decode
CSX_BN_TH[1:0]
1
0
THRESHOLD DIVIDE SETTING
0
0
1
1
0
1
0
1
25%
37.5% (default)
50%
62.5%
5.17.1
Sensor Noise Threshold 1 Register
The Sensor Noise Threshold 1 register controls the noise threshold for Capacitive Touch Sensors 1-4.
Bits 7-6 - CS4_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 4.
Bits 5-4 - CS3_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 3.
Bits 3-2 - CS2_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 2.
Bits 1-0 - CS1_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 1.
5.17.2
Sensor Noise Threshold 2 Register
The Sensor Noise Threshold 2 register controls the noise threshold for Capacitive Touch Sensors 5 - 6.
Bits 3-2 - CS6_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 6.
Revision 1.1 (08-05-09)
SMSC CAP1005 / CAP1006
DATA4S2HEET
SMSC [ SMSC CORPORATION ]
