sx8661 Semtech Corporation, sx8661 Datasheet - Page 24

• Manufacturer Part Number: sx8661
• Description: Low Power, Capacitive Button Touch And Proximity Controller 8 Sensors With Led Drivers And Analog Output
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
3.11 Processing
The first processing step of the raw ticks, coming out of the ASI, is low pass filtering to obtain an estimation of the
average capacitance: tick-ave (see Figure 19).
This slowly varying average is important in the detection of slowly changing environmental changes.
The difference of the tick average and the raw ticks, tick-diff, is a good estimation of rapid changing input
capacitances.
The tick-diff, tick-ave and the configuration parameters in the SPM are then processed and determines the sensor
information, I2C registers status and PWM control.
3.12 Configuration
Figure 20 shows the building blocks used for configuring the SX8661.
The default configuration parameters of the SX8661 are stored in the Quick Start Memory (QSM). This
configuration data is setup to a very common application for the SX8661 with 8 buttons. Without any programming
or host interaction the SX8661 will start up in the Quick Start Application.
The QSM settings are fixed and cannot be changed by the user.
Revision v3.2, January 2011
ASI
processing
compensation DCV
ticks (raw)
low pass
Low Power, Capacitive Button Touch and Proximity Controller
© 2011 Semtech Corp.
Figure 20
Figure 19
tick-ave
tick-diff
Configuration
24
Processing
(8 sensors) with LED Drivers and Analog Output
processing
SPM
PWM LED
controller
controller
GPIO
I2C
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