Multiple Channel Capacitive Touch Sensor and LED Driver
Datasheet
simultaneously exceeding the lid closure threshold. An interrupt can also be generated. During a Lid
Closure Event all touches are blocked.
4.4.3
4.4.4
Grouped Sensors
Capacitive Touch Sensors 8 through 14 inclusive are automatically grouped as a single entity. Each
sensor is sampled independently, however for purposes of activation, recalibration, and repeat rates,
all of them are treated as one group. The Group also has different controls and allows for different
behavior such as sliding, tapping, or press and hold.
Sensing Cycle
Each Capacitive Touch Sensor has controls to be activated and included in the sensing cycle. When
the device is active, it automatically initiates a sensing cycle and repeats the cycle every time it
finishes. The cycle polls through each active Sensor starting with CS1 and extending through CS14.
As each Capacitive Touch Sensor is polled, its measurement is compared against a baseline “not
touched” measurement. If the delta measurement is large enough, then a touch is detected and an
interrupt generated.
4.4.5
Recalibrating Sensors
Each sensor is regularly recalibrated at an adjustable rate. By default, the recalibration routine stores
the average 256 previous measurements and periodically updates the base “Not Touched” setting for
the Capacitive Touch Sensor input. This routine is disabled automatically if a touch is detected
so the touch does not factor into the base “Not Touched” setting.
4.5
Grouped Sensor Behavior
The CAP1014 Grouped sensors function as a single entity that operates differently than the individual
button sensors. This group functions as a slider and offers three different interface functions associated
with it.
4.5.1
Tap
If a touch on any Grouped sensor is detected and held for less than or equal to the M_PRESS bit
settings (default 245ms), then a group press is detected, the TAP bit is set, and an interrupt is
generated. Furthermore, the relative position on the slider is determined and the appropriate UP or
DOWN status bits are set and the appropriate LED is actuated.
No further action is taken. If a slide is subsequently detected, then the TAP status bit is cleared.
4.5.2
Press and Hold
If a touch on any Grouped sensor is held for longer than the M_PRESS bit settings (default 245ms),
then a Group Touch is detected and an interrupt is generated. Furthermore, the relative position on
the slider is determined and the appropriate UP or DOWN status bits are set, the PH bit is set, and
the appropriate LED is actuated.
So long as the Grouped sensor is held, it will flag an interrupt at the programmed repeat rate (as
determined by the RPT_RATE_PH bit settings) indefinitely. Once the touch has been removed, then
the Group is returned to its normal operating condition.
The M_PRESS setting is important to distinguish between Tap, Press & Hold and Sliding. If M_PRESS
is set too low, a Press & Hold may be detected during a slow slide. This will cause user confusion as
the Slide direction and LED may change. Longer M_PRESS settings will ensure that the 3 Group
behaviors are reliably distinct and will add more delay prior to the Press & Hold repeat interrupt
generation.
SMSC CAP1014
Revision 1.65 (08-11-09)
DATA2S3HEET
SMSC [ SMSC CORPORATION ]
