8 Channel Capacitive Touch Sensor with 2 LED Drivers
Datasheet
output control bit for CS2 is ‘1’, and then CS2 is linked to LED2 and no touch is detected, the LED
will not change states. However, the LED state will not change when the sensor pad is touched.
APPLICATION NOTE: If the LED behavior is not “Direct” and the INV_LINK_TRAN bit it ‘0’, the LED will not perform
as expected when the LED2_LTRAN bit is set to ‘1’. Therefore, if breathe and pulse
behaviors are used, set the INV_LINK_TRAN bit to ‘1’.
Bit 0 - LED1_LTRAN - Determines the transition effect when LED1 is linked to CS1.
5.30
LED Mirror Control Register
Table 5.50 LED Mirror Control Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
LED2_
MIR _
EN
LED1_
MIR _
EN
LED Mirror
Control
79h
R/W
-
-
-
-
-
-
00h
The LED Mirror Control Registers determine the meaning of duty cycle settings when polarity is non-
inverted for each LED channel. When the polarity bit is set to ‘1’ (non-inverted), to obtain correct steps
for LED ramping, pulse, and breathe behaviors, the min and max duty cycles need to be relative to
100%, rather than the default, which is relative to 0%.
APPLICATION NOTE: The LED drive assumes that the LEDs are configured such that if the LED pin is driven to
a logic ‘0’, the LED will be on and the CAP1128 LED pin is sinking the LED current. When
the polarity bit is set to ‘1’, it is considered non-inverted. For systems using the opposite LED
configuration, mirror controls would apply when the polarity bit is ‘0’.
These bits are changed automatically if the corresponding LED Polarity bit is changed (unless the
BLK_POL_MIR bit is set - see Section 5.6).
Bit 1 - LED2_MIR_EN - Determines whether the duty cycle settings are “biased” relative to 0% or 100%
duty cycle.
‘0’ (default) - The duty cycle settings are determined relative to 0% and are determined directly with
the settings.
‘1’ - The duty cycle settings are determined relative to 100%.
Bit 0 - LED1_MIR_EN - Determines whether the duty cycle settings are “biased” relative to 0% or 100%
duty cycle.
5.31
LED Behavior Register
Table 5.51 LED Behavior Register
ADDR
81h
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
R/W
LED Behavior 1
-
-
-
-
LED2_CTL[1:0]
LED1_CTL[1:0]
00h
The LED Behavior register controls the operation of LEDs. Each LED pin is controlled by a 2-bit field
and the behavior is determined by whether the LED is linked to a capacitive touch sensor input or not.
If the corresponding LED output is linked to a capacitive touch sensor input, the appropriate behavior
will be enabled / disabled based on touches and releases.
Revision 1.32 (01-05-12)
SMSC CAP1128
DATA6S8HEET
SMSC [ SMSC CORPORATION ]
