Datasheet

8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
SMSC CAP1188 71 Revision 1.32 (01-05-12)
DATASHEET
Bit 2 - LED3_MIR_EN - Determines whether the duty cycle settings are “biased” relative to 0% or 100%
duty cycle.
Bit 1 - LED2_MIR_EN - Determines whether the duty cycle settings are “biased” relative to 0% or 100%
duty cycle.
Bit 0 - LED1_MIR_EN - Determines whether the duty cycle settings are “biased” relative to 0% or 100%
duty cycle.
5.31 LED Behavior Registers
The LED Behavior registers control 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.
If the LED output is not associated with a capacitive touch sensor input, the appropriate behavior will
be enabled / disabled by the LED Output Control register. If the respective LEDx_DR bit is set to a
logic ‘1’, this will be associated as a “touch”, and if the LEDx_DR bit is set to a logic ‘0’, this will be
associated as a “release”.
Table 5.52, "LEDx_CTL Bit Decode" shows the behavior triggers. The defined behavior will activate
when the Start Trigger is met and will stop when the Stop Trigger is met. Note the behavior of the
Breathe Hold and Pulse Release option.
The LED Polarity Control register will determine the non actuated state of the LED outputs (see Section
5.27, "LED Polarity Register").
APPLICATION NOTE: If an LED is not linked to a capacitive touch sensor input and is breathing (via the Breathe
or Pulse behaviors), it must be unactuated and then re-actuated before changes to behavior
are processed. For example, if the LED output is breathing and the Maximum duty cycle is
changed, this change will not take effect until the LED output control register is set to ‘0’ and
then re-set to ‘1’.
APPLICATION NOTE: If an LED is not linked to the capacitive touch sensor input and configured to operate using
Pulse 1 Behavior, then the circuitry will only be actuated when the corresponding output
control bit is set. It will not check the bit condition until the Pulse 1 behavior is finished. The
device will not remember if the bit was cleared and reset while it was actuated.
APPLICATION NOTE: If an LED is actuated and not linked and the desired LED behavior is changed, this new
behavior will take effect immediately; however, the first instance of the changed behavior
may act incorrectly (e.g. if changed from Direct to Pulse 1, the LED output may ‘breathe’ 4
times and then end at minimum duty cycle). LED Behaviors will operate normally once the
LED has been un-actuated and then re-actuated.
APPLICATION NOTE: If an LED is actuated and it is switched from linked to a capacitive touch sensor input to
unlinked (or vice versa), the LED will respond to the new command source immediately if
the behavior was Direct or Breathe. For Pulse behaviors, it will complete the behavior
already in progress. For example, if a linked LED was actuated by a touch and the control
Table 5.51 LED Behavior Registers
ADDR R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAULT
81h R/W LED Behavior 1 LED4_CTL[1:0] LED3_CTL[1:0] LED2_CTL[1:0] LED1_CTL[1:0] 00h
82h R/W LED Behavior 2 LED8_CTL[1:0] LED7_CTL[1:0] LED6_CTL[1:0] LED5_CTL[1:0] 00h