CAP1214 Datasheet, PDF (29/107 Pages) SMSC Corporation – Multiple Channel Capacitive Touch Sensor and LED Driver

Multiple Channel Capacitive Touch Sensor and LED Driver
Datasheet
Based on the multiple button touch settings (see Section 6.23), both CS8 and CS14 may detect a
touch simultaneously and both UP and DOWN status bits may be set.
5.7
FEEDBACK Pin
The FEEDBACK pin can drive an external device (such as a piezo transducer) to generate feedback
(sound or vibration) to the final application user. The FEEDBACK pin can be driven when a touch is
detected (see Section 6.41, "Feedback Channel Configuration Registers"), or it can be driven by the
host (see Section 6.42, "Feedback One-Shot Register"). Duration and frequency of the output are
programmable (see Section 6.40, "Feedback Configuration Register").
When activated, the FEEDBACK pin drives a 50% duty cycle signal at the programmed frequency for
the programmed duration.
5.8
5.8.1
ALERT Pin
The ALERT pin is an active high output that asserts when an interrupt event is detected. It is also used
to wake the device from Deep Sleep state.
Whenever an interrupt is generated, the INT bit (see Section 6.1) is set. The ALERT pin is cleared
when INT bit is cleared by the user. Additionally, if no press is detected, the status bits are cleared
when the INT bit is cleared.
Button Interrupt Behavior
For non-grouped buttons, an interrupt is generated when a touch is detected. If the repeat rate is
enabled (see Section 6.14), then, so long as the touch is held, another interrupt will be generated
based on the programmed repeat rate (see Figure 5.2) and upon release. If repeat rate is not enabled,
an interrupt is generated when a touch is detected and optionally, can be generated at release (see
Section 6.33 and Figure 5.3).
Interrupt on
Touch
Polling Cycle
(35ms)
Touch Detected
Button Repeat Rate
(175ms)
ALERT Pin /
INT bit
Button Repeat Rate Button Repeat Rate
(175ms)
(175ms)
Button Status
SMBus Write to
INT bit
Figure 5.2 Button Interrupt Behavior - Repeat Rate Enabled
Optional
Interrupt on
Release
SMSC CAP1214
29
DATASHEET
Revision 1.0 (08-30-10)