8 Channel Capacitive Touch Sensor with 2 LED Drivers
Datasheet
the pin is set to the “inactive” state (logic ‘0’), then the pin will be left in a High Z state and pulled
high via an external pull-up resistor.
‘1’ - The LED2 pin is a push-pull output. When driving a logic ‘1’, the pin is driven high. When
driving a logic ‘0’, the pin is driven low.
Bit 0 - LED1_OT - Determines the output type of the LED1 pin.
5.26
Sensor Input LED Linking Register
Table 5.45 Sensor Input LED Linking Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Sensor
Input LED
Linking
CS2_
LED2
CS1_
LED1
72h
R/W
-
-
-
-
-
-
00h
The Sensor Input LED Linking register controls whether a capacitive touch sensor input is linked to an
LED output. If the corresponding bit is set, then the appropriate LED output will change states defined
by the LED Behavior controls (see Section 5.31) in response to the capacitive touch sensor input.
Bit 1 - CS2_LED2 - Links the LED2 output to a detected touch on the CS2 sensor input. When a touch
is detected, the LED is actuated and will behave as determined by the LED Behavior controls.
‘0’ (default) - The LED 2 output is not associated with the CS2 input. If a touch is detected on the
CS2 input, the LED will not automatically be actuated. The LED is enabled and controlled via the
LED Output Control register (see Section 5.28) and the LED Behavior registers (see Section 5.31).
‘1’ - The LED 2 output is associated with the CS2 input. If a touch is detected on the CS2 input,
the LED will be actuated and behave as defined in Table 5.52.
Bit 0 - CS1_LED1 - Links the LED1 output to a detected touch on the CS1 sensor input. When a touch
is detected, the LED is actuated and will behave as determined by the LED Behavior controls.
5.27
LED Polarity Register
Table 5.46 LED Polarity Register
ADDR
R/W
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
LED2_
POL
LED1_
POL
73h
LED Polarity
-
-
-
-
-
-
00h
The LED Polarity register controls the logical polarity of the LED outputs. When these bits are set or
cleared, the corresponding LED Mirror controls are also set or cleared (unless the BLK_POL_MIR bit
is set - see Section 5.6, "Configuration Registers"). Table 5.48, "LED Polarity Behavior" shows the
interaction between the polarity controls, output controls, and relative brightness.
APPLICATION NOTE: The polarity controls determine the final LED pin drive. A touch on a linked capacitive touch
sensor input is treated in the same way as the LED Output Control bit being set to a logic ‘1’.
APPLICATION NOTE: The LED drive assumes that the LEDs are configured such that if the LED pin is driven to
a logic ‘0’ then the LED will be on and that the CAP1128 LED pin is sinking the LED current.
Conversely, if the LED pin is driven to a logic ‘1’, the LED will be off and there is no current
flow. See Figure 4.1, "System Diagram for CAP1128".
SMSC CAP1128
Revision 1.32 (01-05-12)
DATA6S5HEET
SMSC [ SMSC CORPORATION ]
