SEMTECH SX8661I07AULTRT

SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
GENERAL DESCRIPTION
KEY PRODUCT FEATURES
The SX8661 is an ultra low power, fully integrated 8channel solution for capacitive touch-button and
proximity detection applications. Unlike many
capacitive touch solutions, the SX8661 features
dedicated capacitive sense inputs (that requires no
external components) in addition to 8 general
purpose I/O ports (GPIO). Each of the 8 on-chip
GPIO/LED driver is equipped with independent PWM
source for enhanced visual effect such as dimming,
and breathing.
 Complete 8 Sensors Capacitive Touch-Button Solution
The SX8661 includes a capacitive 10 bit ADC analog
interface with automatic compensation up to 100pF.
The high resolution capacitive sensing supports a
wide variety of touch pad sizes and shapes and
allows capacitive buttons to be created using thick
overlay materials (up to 5mm) for an extremely
robust and ESD immune system design.
The SX8661 incorporates a versatile firmware that
was specially designed to simplify capacitive touch
solution design and offers reduced time-to-market.
Integrated
multi-time
programmable
memory
provides the ultimate flexibility to modify key firmware
parameters (gain, threshold, scan period, auto offset
compensation) in the field without the need for new
firmware development.
The SX8661 supports the 400 kHz I²C serial bus
data protocol and includes a field programmable
slave address. The tiny 4mm x 4mm footprint makes
it an ideal solution for portable, battery powered
applications where power and density are at a
premium.
o Up to 8 LED Drivers for individual Visual Feedback with
Auto Lightening
o Configurable Single or Continuous Fading Mode
o 256 steps PWM Linear and Logarithmic control
 Proximity Sensing up to several centimetres
 High Resolution Capacitive Sensing
o Up to 100pF of Offset Cap. Compensation at Full
Sensitivity
o Capable of Sensing up thru 5mm thick Overlay Materials
 Up to 2 Analog Output Interfaces (AOI-A and AOI-B)
o Enable button detection thru host’s ADC
 Support of buzzer for audible feedback
 User-selectable Button Reporting Configuration
o Report Single or Report Strongest
 Extremely Low Power
o 8uA (typ) in Sleep Mode
o 70uA (typ) in Doze Mode (195ms)
o 200uA (typ) in Active Mode (30ms)
 Programmable Scanning Period from 15ms to several seconds
 Auto Offset Compensation
o Eliminates false triggers due to environmental factors
(temperature, humidity)
o Initiated on power-up and configurable intervals
 Multi-Time In-Field Programmable Firmware Parameters
for Ultimate Flexibility
o On-chip user programmable memory for fast, self
contained start-up
 No External Components per Sensor Input
 Internal Clock Requires No External Components
 Differential Sensor Sampling for Reduced EMI
TYPICAL APPLICATION CIRCUIT
 Optional 400 KHz I²C Interface with Programmable Address
 -40°C to +85°C Operation
APPLICATIONS
 LCD TVs, Monitors
 White Goods
 Notebook/Netbook/Portable/Handheld computers
 Consumer Products, Instrumentation, Automotive
 Mechanical Button Replacement
ORDERING INFORMATION
Part Number
Temperature
Range
Package
1
SX8661I07AULTRT -40°C to +85°C Lead Free MLPQ-UT28
1
3000 Units/reel
* This device is RoHS/WEEE compliant and Halogen Free
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
Table of Contents
GENERAL DESCRIPTION ........................................................................................................................ 1
TYPICAL APPLICATION CIRCUIT ............................................................................................................ 1
KEY PRODUCT FEATURES..................................................................................................................... 1
APPLICATIONS....................................................................................................................................... 1
ORDERING INFORMATION...................................................................................................................... 1
1
GENERAL DESCRIPTION............................................................................................................... 5
1.1
1.2
1.3
1.4
1.5
2
Pin Diagram
Marking information
Pin Description
Simplified Block Diagram
Acronyms
5
5
6
7
7
ELECTRICAL CHARACTERISTICS ................................................................................................. 8
2.1
2.2
2.3
2.4
3
Absolute Maximum Ratings
Recommended Operating Conditions
Thermal Characteristics
Electrical Specifications
8
8
8
9
FUNCTIONAL DESCRIPTION ........................................................................................................ 12
3.1
3.2
Quickstart Application
Introduction
3.2.1
General
3.2.2
GPIOs
3.2.3
Analog Output Interface A and B (SPO mode)
3.2.4
Buzzer (SPO mode)
3.2.5
Parameters
3.2.6
Configuration
3.3
Scan Period
3.4
Operation modes
3.5
Sensors on the PCB
3.6
Button Information
3.7
Buzzer
3.8
Analog Output Interface
3.9
Analog Sensing Interface
3.10
Offset Compensation
3.11
Processing
3.12
Configuration
3.13
Power Management
3.14
Clock Circuitry
3.15
I2C interface
3.16
Interrupt
3.16.1 Power up
3.16.2 Assertion
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
3.16.3 Clearing
3.16.4 Example
3.17
Reset
3.17.1 Power up
3.17.2 RESETB
3.17.3 Software Reset
3.18
General Purpose Input and Outputs
3.18.1 GPP mode
3.18.2 GPO Dual Reporting
3.18.3 GPO Fading
3.18.4 Intensity index vs PWM pulse width
3.18.5 GPO Triple Reporting
4
DATASHEET
27
28
28
28
29
29
30
30
32
33
34
35
PIN DESCRIPTIONS ..................................................................................................................... 37
4.1
4.2
4.3
4.4
4.5
5
Introduction
ASI pins
Host interface pins
Power management pins
General purpose IO pins
37
37
38
41
42
DETAILED CONFIGURATION DESCRIPTIONS .............................................................................. 43
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
6
Introduction
General Parameters
Capacitive Sensors Parameters
Proximity Parameters
Button Parameters
Analog Output Interface Parameters
Buzzer Parameters
Mapping Parameters
GPIO Parameters
43
46
47
51
53
59
61
62
64
I2C INTERFACE ........................................................................................................................... 68
6.1
6.2
6.3
6.4
6.5
6.6
I2C Write
I2C read
I2C Registers Overview
Status Registers
Control Registers
SPM Gateway Registers
6.6.1
SPM Write Sequence
6.6.2
SPM Read Sequence
6.7
NVM burn
7
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69
70
71
73
75
76
77
78
APPLICATION INFORMATION ...................................................................................................... 79
7.1
7.2
Triple proximity reporting
Dual proximity reporting
7.2.1
SPM file (application two AOI, dual proximity reporting)
7.3
Example of Touch+Proximity Module
7.3.1
Overview
7.3.2
Operation
7.3.3
Performance
7.3.4
Schematics
7.3.5
Layout
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
8
REFERENCES ............................................................................................................................. 86
9
PACKAGING INFORMATION ........................................................................................................ 87
9.1
9.2
Package Outline Drawing
Land Pattern
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
1 GENERAL DESCRIPTION
cap4
4
cap5
5
cap6
6
cap7
7
vana
resetb
gnd
vdig
gpio7
gpio6
23
22
SX8661
Top View
bottom ground pad
8
9
10
11
12
13
14
gpio0
3
24
sda
cap3
25
scl
2
26
intb
cap2
27
vdd
1
28
cp
cap1
cap0
Pin Diagram
cn
1.1
21
gnd
20
gpio5
19
gpio4
18
gpio3
17
gpio2
16
gnd
15
gpio1
Figure 1 Pinout Diagram
1.2
Marking information
NC5B
yyww
xxxxx
R07
yyww = Date Code
xxxxx = Semtech lot number
R07 = Semtech Code
Figure 2 Marking Information
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
1.3
DATASHEET
Pin Description
Number
Name
Type
Description
1
CAP1
Analog
Capacitive Sensor 1
2
CAP2
Analog
Capacitive Sensor 2
3
CAP3
Analog
Capacitive Sensor 3
4
CAP4
Analog
Capacitive Sensor 4
5
CAP5
Analog
Capacitive Sensor 5
6
CAP6
Analog
Capacitive Sensor 6
7
CAP7
Analog
Capacitive Sensor 7
8
CN
Analog
Integration Capacitor, negative terminal (1nF between CN and CP)
9
CP
Analog
Integration Capacitor, positive terminal (1nF between CN and CP)
10
VDD
Power
Main input power supply
11
INTB
Digital Output
Interrupt, active LOW, requires pull up resistor (in host or external)
12
SCL
Digital Input
I2C Clock, requires pull up resistor (in host or external)
13
SDA
Digital Input/Output
I2C Data, requires pull up resistor (in host or external)
14
GPIO0
Digital Input/Output
General Purpose Input/Output 0
15
GPIO1
Digital Input/Output
General Purpose Input/Output 1
16
GND
Ground
Ground
17
GPIO2
Digital Input/Output
General Purpose Input/Output 2
18
GPIO3
Digital Input/Output
General Purpose Input/Output 3
19
GPIO4
Digital Input/Output
General Purpose Input/Output 4
20
GPIO5
Digital Input/Output
General Purpose Input/Output 5
21
GND
Ground
Ground
22
GPIO6
Digital Input/Output
General Purpose Input/Output 6
23
GPIO7
Digital Input/Output
General Purpose Input/Output 7
24
VDIG
Analog
Digital Core Decoupling, connect to a 100nF decoupling capacitor
25
GND
Ground
Ground
26
RESETB
Digital Input
Active Low Reset. Connect to VDD if not used.
27
VANA
Analog
Analog Core Decoupling, connect to a 100nF decoupling capacitor
28
CAP0
Analog
Capacitive Sensor 0
Ground
Exposed pad connect to ground
bottom plate GND
Table 1 Pin description
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
1.4
DATASHEET
Simplified Block Diagram
gpo7
gpo6
scl
sda
vdig
intb
gnd
vdd
cp
cn
vana
resetb
The simplified block diagram of the SX8661 is illustrated in Figure 3.
Figure 3 Simplified block diagram of the SX8661
1.5
AOI
ASI
DCV
GPO
GPP
MTP
NVM
PWM
QSM
SPM
SPO
Acronyms
Analog Output Interface
Analog Sensor Interface
Digital Compensation Value
General Purpose Output
General Purpose PWM
Multiple Time Programmable
Non Volatile Memory
Pulse Width Modulation
Quick Start Memory
Shadow Parameter Memory
Special Purpose Output
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
2 ELECTRICAL CHARACTERISTICS
2.1
Absolute Maximum Ratings
Stresses above the values listed in “Absolute Maximum Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of the device at these, or any other conditions beyond the “Recommended
Operating Conditions”, is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device
reliability.
Parameter
Symbol
Min.
Max.
Unit
Supply Voltage
VDD
-0.5
3.9
V
Input voltage (non-supply pins)
VIN
-0.5
3.9
V
Input current (non-supply pins)
IIN
10
mA
Operating Junction Temperature
TJCT
125
°C
Reflow temperature
TRE
260
°C
Storage temperature
TSTOR
-50
150
°C
ESDHBM
3
kV
ILU
± 100
mA
ESD HBM (Human Body model)
Latchup
(i)
(ii)
Table 2 Absolute Maximum Ratings
(i) Tested to JEDEC standard JESD22-A114
(ii) Tested to JEDEC standard JESD78
2.2
Recommended Operating Conditions
Parameter
Symbol
Min.
Max.
Unit
Supply Voltage
VDD
2.7
3.6
V
100
mV
Supply Voltage Drop
(iii, iv, v)
VDDdrop
Supply Voltage for NVM programming
VDD
3.0
3.6
V
Ambient Temperature Range
TA
-40
85
°C
Table 3 Recommended Operating Conditions
(iii) Performance for 2.6V < VDD < 2.7V might be degraded.
(iv) Operation is not guaranteed below 2.6V. Should VDD briefly drop below this minimum value, then the SX8661 may
require;
- a hardware reset issued by the host using the RESETB pin
- a software reset issued by the host using the I2C interface
(v) In the event the host processor is reset or undergoes a power OFF/ON cycle, it is recommended that the host also resets
the SX8661 and assures that parameters are re-written into the SPM (should these differ to the parameters held in NVM).
2.3
Thermal Characteristics
Parameter
Thermal Resistance - Junction to Ambient
Symbol
(vi)
θJA
Min.
Max.
Unit
25
°C/W
Table 4 Thermal Characteristics
(vi) Static airflow
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
2.4
DATASHEET
Electrical Specifications
All values are valid within the operating conditions unless otherwise specified.
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
IOP,active
30ms scan period,
8 sensors enabled,
common sensitivity 0
proximity sensing OFF
200
275
uA
Doze mode, average
IOP,Doze
195ms scan period,
8 sensors enabled,
common sensitivity 0
proximity sensing OFF
70
100
uA
Sleep
IOP,sleep
I2C listening,
sensors disabled
8
17
uA
IQS,active
30ms scan period,
8 sensors enabled,
sensitivity 2 for buttons
sensitivity 7 for proximity
proximity sensing ON
800
1100
uA
IQS,Doze
195ms scan period,
8 sensors enabled,
sensitivity 2 for buttons
sensitivity 7 for proximity
proximity sensing ON
160
220
uA
0.7*VDD
VDD + 0.3
V
VSS - 0.3
0.8
V
±1
uA
Current consumption
Active mode, average
Active mode, average
(Quick Start application)
Doze mode, average
(Quick Start application)
ResetB, SCL, SDA
Input logic high
VIH
Input logic low
VIL
VSS applied to GND pins
Input leakage current
LI
CMOS input
Pull up resistor
RPU
when enabled
660
kΩ
Pull down resistor
RPD
when enabled
660
kΩ
Output logic high
VOH
IOH<4mA
Output logic low
VOL
GPIO set as Output, IntB, SDA
VDD-0.4
IOL,GPIO<12mA
V
0.4
V
275
ms
IOL,SDA,INTB<4mA
Start-up
Power up time
tpor
time between rising edge
VDD and rising INTB
RESETB
ResetB pulse width
Revision v3.2, January 2011
tres
50
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
Parameter
Symbol
Conditions
DATASHEET
Min.
Typ.
Max.
Unit
Recommended External components
capacitor between VDIG, GND
Cvdig
type 0402, tolerance +/-50%
100
nF
capacitor between VANA, GND
Cvana
type 0402, tolerance +/-50%
100
nF
capacitor between CP, CN
Cint
type 0402, COG, tolerance +/-5%
1
nF
capacitor between VDD, GND
Cvdd
type 0402, tolerance +/-50%
100
nF
Table 5 Electrical Specifications
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
Parameter
I2C Timing Specifications
Symbol
Conditions
DATASHEET
Min.
Typ.
Max.
Unit
400
KHz
(i)
SCL clock frequency
fSCL
SCL low period
tLOW
1.3
us
SCL high period
tHIGH
0.6
us
Data setup time
tSU;DAT
100
ns
Data hold time
tHD;DAT
0
ns
Repeated start setup time
tSU;STA
0.6
us
Start condition hold time
tHD;STA
0.6
us
Stop condition setup time
tSU;STO
0.6
us
Bus free time between stop and start
tBUF
500
us
Input glitch suppression
tSP
50
ns
Table 6 I2C Timing Specification
Notes:
(i) All timing specifications, Figure 4 and Figure 5, refer to voltage levels (VIL, VIH, VOL) defined in Table 5.
The interface complies with slave F/S mode as described by NXP: “I2C-bus specification, Rev. 03 - 19 June 2007”
Figure 4 I2C Start and Stop timing
Figure 5 I2C Data timing
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
3 FUNCTIONAL DESCRIPTION
3.1
Quickstart Application
The SX8661 is preconfigured (Quickstart Application) for an application requiring proximity and seven buttons,
with one Analog Output Interface and seven LED drivers using PWM fading. Table 7 summarises the default
configuration of the eight GPIOs available on the SX8661 Quickstart application.
GPIO
Function Fading Mode
Comments
0
LED
Single Fading Mode
Autolight, mapped on Btn1 (100% ON) and proximity (50% ON)
1
LED
Single Fading Mode
Autolight, mapped on Btn2 (100% ON) and proximity (50% ON)
2
LED
Single Fading Mode
Autolight, mapped on Btn3 (100% ON) and proximity (50% ON)
3
LED
Single Fading Mode
Autolight, mapped on Btn4 (100% ON) and proximity (50% ON)
4
LED
Single Fading Mode
Autolight, mapped on Btn5 (100% ON) and proximity (50% ON)
5
LED
Single Fading Mode
Autolight, mapped on Btn6 (100% ON) and proximity (50% ON)
6
LED
Single Fading Mode
Autolight, mapped on Btn7 (100% ON) and proximity (50% ON)
Not applicable
Analog Output Interface A (VDD=3.3V)
Prox = Idle : 3.3V
Btn1: 0.6V
Btn2: 0.9V
Btn3: 1.2V
Btn4: 1.5V
Btn5: 1.8V
Btn6: 2.1V
Btn7: 2.4V
7
AOI-A
Table 7 Quickstart Application GPIO configuration
Implementing a schematic based on Figure 6 will be immediately operational after powering without programming
the SX8661 (even without host).
The default sensitivity is set to 0x02 for all button sensors (assumed button sensor area approximately 1 cm
2
covered by 2mm thick acrylic overlay material) and 0x07 for the proximity sensor (typical 4 x 8 cm ).
Figure 6 Quickstart Application
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
Figure 7 Quickstart LED and AOI reporting
Figure 7 shows the reporting on the LEDs and the AOI for the quickstart application.
The LEDs operate in triple reporting mode. In triple reporting mode the LEDs have three light intensities.
- OFF: out of proximity, no touch,
- Proximity: proximity detected,
- ON: button touched.
In case no fingers/hand is detected (out of proximity) all LEDs will be OFF and the AOI indicates the idle level.
In case a finger/hand is approaching proximity is detected and all LEDs will light up to 50% of the maximum
intensity. The AOI goes to the proximity voltage level (in the quickstart application the proximity level is chosen
identical to the idle level).
In case a button is touched the corresponding LED will go to 100% of intensity and the AOI voltage level indicates
the button that is touched.
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
3.2
3.2.1
DATASHEET
Introduction
General
The SX8661 is intended to be used in applications which require capacitive sensors covered by isolating overlay
material and which need to detect the proximity of a finger/hand though the air. A finger approaching the
capacitive sensors will change the charge that can be loaded on the sensors. The SX8661 measures the change
of charge and converts that into digital values (ticks). The larger the charge on the sensors, the larger the number
of ticks will be. The charge to ticks conversion is done by the SX8661 Analog Sensor Interface (ASI).
The ticks are further processed by the SX8661 and converted in a high level, easy to use information for the
user’s host.
The information between SX8661 and the user’s host is passed through the I2C interface with an additional
interrupt signal indicating that the SX8661 has new information. For buttons this information is simply touched or
released. The SX8661 can operate without the I2C and interrupt by using the analog output interface (GPIO7
and/or GPIO6) which voltage level indicates the button touched or GPO with the autolight function.
3.2.2
GPIOs
Feedback to the user is using General Purpose Input Output (GPIO) pins. The SX8661 offers up to eight
individual configurable GPIO pins. The GPIO can e.g. be set as a LED driver which slowly fade-in when a finger
touches a button or proximity is detected and slowly fade-out when the button is released or finger goes out of
proximity. Fading intensity variations can be logarithmic or linear. Interval speed and initial and final light intensity
can be selected by the user. The fading is done using a 256 step PWM. The SX8661 has eight individual PWM
generators, one for each GPIO pin.
The LED fading-in and fading-out mode is called the GPO (fading) mode.
The LED fading can be initiated automatically by the SX8661 by setting the SX8661 autolightening feature. A
simple touch on a sensor and the corresponding LED will fade-in without any host interaction over the I2C.
In case the autolightening feature is disabled then the host will decide to start a LED fading-in period, simply by
setting the GPO pin to ‘high’ using one I2C command. The SX8661 will then slowly fade-in the LED using the
PWM autonomously.
In case the host needs to have full control of the LED intensity then the host can set the GPIO in the PWM mode
(GPP). The host is then able to set the PWM pulse width freely at the expense of an increased I2C occupation.
The GPIOs can be set further in special purpose output (SPO) for the buzzer or analog output interface.
3.2.3
Analog Output Interface A and B (SPO mode)
The Analog Output Interface (AOI) is a PWM output signal between ground and VDD. The duty cycle of the AOI
output will change depending on which button is touched. A host controller can then measure the mean voltage
delivered on the AOI output and determine which button is touched at any given time.
The AOI feature allows the SX8661 device to replace directly legacy mechanical button controllers in a quick and
effortless manner. The SX8661 supports up to two Analog Output Interfaces, AOI-A and AOI-B (on GPIO7 and
GPIO6 respectively). The SX8661 allows buttons to be mapped on either AOI-A or AOI-B. The button mapping as
well as the mean voltage level that each button produces on a AOI output can be configured by the user through a
set of parameters described in later chapters (see 5.6).
3.2.4
Buzzer (SPO mode)
The SX8661 can drive a buzzer (on GPIO5) to provide audible feedback on button touches. The buzzer duration
is set to approximately 30ms per default (see 5.7).
3.2.5
Parameters
The SX8661 has many low level built-in, fixed algorithms and procedures. To allow a lot of freedom for the user
and adapt the SX8661 for different applications these algorithms and procedures can be configured with a large
set of parameters which will be described in the following sections. Examples of parameters are which sensors
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
are buttons, which GPIO is used for outputs, for the Analog Output Interfaces, the Buzzer or LEDs and which
GPIO is mapped to which button.
Sensitivity and detection thresholds of the sensors are part of these parameters. Assuming that overlay material
and sensors areas are identical then the sensitivities and thresholds will be the same for each sensor. In case
sensors are not of the same size then sensitivities or thresholds might be chosen individually per sensor.
So a smaller size sensor can have a larger sensitivity while a big size sensor may have the lower sensitivity.
3.2.6
Configuration
During a development phase the parameters can be determined and fine tuned by the users and downloaded
over the I2C in a dynamic way. The parameter set can be downloaded over the I2C by the host each time the
SX8661 boots up. This allows a flexible way of setting the parameters at the expense of I2C occupation.
In case the parameters are frozen they can be programmed in Multiple Time Programmable (MTP) Non Volatile
Memory (NVM) on the SX8661. The programming needs to be done once (over the I2C). The SX8661 will then
boot up from the NVM and additional parameters from the host are not required anymore.
In case the host desires to overwrite the boot-up NVM parameters (partly or even complete) this can be done by
additional I2C communications.
3.3
Scan Period
The basic operation Scan period of the SX8661 sensing interface can be split into three periods over time.
In the first period (Sensing) the SX8661 is sensing all enabled CAP inputs, from CAP0 towards CAP7.
In the second period (Processing) the SX8661 processes the sensor data, verifies and updates the GPIO and the
I2C.
In the third period (Timer) the SX8661 is set in a low power mode and waits until a new cycle starts.
Figure 8 shows the different SX8661 periods over time.
Figure 8 Scan Period
The scan period determines the minimum reaction time of the SX8661. The scan period can be configured by the
host from 15ms to values larger than a second.
The reaction time is defined as the interval between a touch on the sensor and the moment that the SX8661
generates the interrupt on the INTB pin. The shorter the scan period the faster the reaction time will be.
Very low power consumptions can be obtained by setting very long scan periods with the expense of having
longer reaction times.
All external events like GPIO, I2C and the interrupt are updated in the processing period, so once every scan
period.
3.4
Operation modes
The SX8661 has 3 operation modes. The main difference is found in the reaction time (corresponding to the scan
period) and power consumption.
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Active mode offers fast scan periods. The typical reaction time is 30ms. All enabled sensors are scanned and
information data is processed within this interval.
Doze mode increases the scan period time which increases the reaction time to 195ms typical and at the same
time reduces the operating current.
Sleep mode turns the SX8661 OFF, except for the I2C peripheral, minimizing operating current while maintaining
the power supplies. In Sleep mode the SX8661 does not do any sensor scanning. The Sleep mode will be exited
by any I2C access.
The user can specify other scan periods for the Active and Doze mode and decide for other compromises
between reaction time and power consumption.
In most applications the reaction time needs to be fast when fingers are present, but can be slow when no person
uses the application. In case the SX8661 is not used for a specific time it will go from Active mode into Doze
mode and power will be saved. This time-out is determined by the Passive Timer which can be configured by the
user or turned OFF if not required.
To leave Doze mode and enter Active mode this can be done by a simple touch on any button.
The host can decide to force the operating mode by issuing commands over the I2C (using register GpioOpMode)
and take fully control of the SX8661. The diagram in Figure 9 shows the available operation modes and the
possible transitions.
Figure 9 Operation modes
3.5
Sensors on the PCB
The capacitive sensors are relatively simple copper areas on the PCB connected to the eight SX8661 capacitive
sensor input pins (CAP0…CAP7).The sensors are covered by isolating overlay material (typically 1mm...3mm).
The area of a sensor is typically one square centimetre which corresponds about to the area of a finger touching
the overlay material. The area of a proximity sensor is usually a factor larger as the smaller touch sensors.
The capacitive sensors can be setup as ON/OFF buttons for touch sensing and CAP0 offers additionally proximity
sensing (see example Figure 10) for control applications.
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Figure 10 PCB top layer of three touch buttons sensors surrounded by a proximity sensor
Please refer to the layout guidelines application note [1], for more details.
3.6
Button Information
The touch buttons have two simple states (see Figure 11): ON (touched by finger) and OFF (released and no
finger press).
Figure 11 Buttons
A finger is detected as soon as the number of ticks from the ASI reaches a user-defined threshold plus a
hysteresis.
A release is detected if the tick from the ASI goes below the threshold minus a hysteresis. The hysteresis around
the threshold avoids rapid touch and release signalling during transients.
Buttons can also be used to do proximity sensing. The principle of proximity sensing operation is exactly the same
as for touch buttons except that proximity sensing is done several centimeters above the overlay through the air.
ON state means that finger/hand is detected by the sensor and OFF state means the finger/hand is far from the
sensor and not detected.
3.7
Buzzer
The SX8661 has the ability to drive a buzzer (on GPIO5) to provide an audible indication that a button has been
touched. The buzzer is driven by a square signal for approximately 30ms (default). During the first phase (15ms)
the signal’s frequency is default 4KHz while in the second phase (15ms) the signal’s frequency default is 8KHz.
The buzzer is activated only once during any button touch and is not repeated for long touches. The user can
choose to enable or disable the buzzer by configuration and define the idle level, frequencies and phase durations
(see 5.7).
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Figure 12 Buzzer behavior
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3.8
DATASHEET
Analog Output Interface
The Analog Output Interface outputs a PWM signal with a varying duty cycle depending on which button is
touched. By filtering (with a simple RC filter) the PWM signal results in a DC voltage, different for each button
touch. The host controller measures the DC voltage level and determines which buttons has been touched.
In the case of single button touches, each button produces its own voltage level as configured by the user (see
5.6 and Table 8).
Figure 13 show how the AOI will behave when the user touches and releases different buttons.
The AOI will switch between the AOI idle level and the level for each button.
Figure 13 AOI behavior
The PWM blocks used in AOI modes are 8-bits based and clocked at 2MHz typically.
The PWM period can be set to 256 (default) or 64. The 256 period offers a better granularity at a lower frequency,
while the 64 period is faster and with fewer steps.
Figure 14 shows the PWM definition of the AOI.
Figure 14 PWM definition, (a) small pulse width, (b) large pulse width
Table 8 describes the AOI level index versus the PWM pulse width. The user can select 256 steps (index) in case
the period is set to 255.
In case the period is set to 64 then the index from 0 to 63 applies.
Index
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Width
0
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Index
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Width
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
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Index
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
Width
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
Index
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
Width
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
Index
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
Width
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
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Index
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
Width
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
Index
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
Width
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
Index
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
Width
225
226
227
228
229
230
231
232
233
234
235
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Index
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Width
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Index
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
Width
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
Index
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
Width
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
Index
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
Width
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
Index
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
Width
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
DATASHEET
Index
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
Width
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
Index
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
Width
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
Index
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
Width
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
Table 8 AOI Level index vs. PWM pulse width (normal polarity)
The AOI reports always one button. The AOI can be split over two GPIO pins (AOI-A, AOI-B). The AOI-A interface
is connected to pin GPIO7 and the AOI-B is connected to pin GPIO6. The user can map any button to either AOIA or AOI-B or both.
In case buttons are split to both AOI pins, multiple button touches are still resulting in one AOI reporting.
In most applications only one AOI pin will be selected. The two AOI pins allow the user a more coarse detection
circuitry at the host. Assuming a 3.3V supply and 8 buttons on one single AOI then the AOI levels could be
separated with around 0.3…0.4V. In case of using the two AOI pins, 4 buttons could be mapped on AOI-A
separated with around 0.8V (similar for 4 buttons on AOI-B) which step is about the double in case of a single
AOI.
In case of a single touch the reported button is straight forward (as in Figure 13).
If more than one button is touched the reported depends on the selected button reporting mode parameter (5.5).
Three reporting modes exist for the SX8661 (All, Single and Strongest).
The All reporting mode is applicable only for the I2C reporting (AOI is not available). In All-mode all buttons that
are touched are reported in the I2C buttons status bits.
In the Single-mode a single touched button will be reported on the AOI and the I2C. All touches that occur
afterwards will not be reported as long as the first touch sustains. Only when the first reported button is released
will the SX860 report another touch.
Figure 15 shows the Single-mode reporting in case of 2 touches occurring over time.
Figure 15 Single-mode reporting with 2 touches
At time t1 button0 is touched and reported on the AOI. At time t2 button1 is touched as well but not reported. At
time t3 the button0 is released and button1 will be reported immediately (or after one scan period at idle level).
At time t4 both buttons are released and the AOI reports the idle level.
The button with the lowest Cap pin index will be reported in case of a simultaneous touch (that means touches
occurring within the same scan period).
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In the Strongest-mode the strongest touched button will be reported on the AOI and the I2C. All touches that
occur afterwards representing a weaker touch will not be reported. Only a touch which is stronger will be reported
by the SX860.
Figure 16 shows the Strongest-mode reporting in case of 2 touches (with bt1 the strongest touch).
Figure 16 Strongest-mode reporting with 2 touches
At time t1 button0 is touched and reported on the AOI. At time t2 button1 is touched as well. As bt1 is the
strongest touch it will be reported on the AOI immediately (or after one scan period at idle level). At time t3 the
button0 is released while the AOI continues to report button1. At time t4 both buttons are released and the AOI
reports the idle level.
In some special cases (when the buzzer is suspected to load heavily the power supply) the user may choose the
AOI to go to 0V, to VDD or to the AOI idle level for the duration the buzzer is active.
Figure 17 AOI behavior with 0V buzzer state
In Figure 17 the AOI will go to 0V each time the buzzer is active. The AOI returns then to either the idle mode for
one scan period or goes immediately to the PWM button level.
In case the SX8661 is set to sleep mode the AOIs will go to 0V.
3.9
Analog Sensing Interface
The Analog Sensing Interface (ASI) converts the charge on the sensors into ticks which will be further digitally
processed. The basic principle of the ASI will be explained in this section.
The ASI consists of a multiplexer selecting the sensor, analog switches, a reference voltage, an ADC sigma delta
converter, an offset compensation DAC and an external integration capacitor (see Figure 18).
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Figure 18 Analog Sensor Interface
To get the ticks representing the charge on a specific sensor the ASI will execute several steps.
The charge on a sensor cap (e.g CAP0) will be accumulated multiple times on the external integration capacitor,
Cint.
This results in an increasing voltage on Cint proportional to the capacitance on CAP0.
At this stage the offset compensation DAC is enabled. The compensation DAC generates a voltage proportional
to an estimation of the external capacitance. The estimation is obtained by the offset compensation procedure
executed e.g. at power-up.
The difference between the DAC output and the charge on Cint is the desired signal. In the ideal case the
difference of charge will be converted to zero ticks if no finger is present and the number of ticks becomes high in
case a finger is present.
The difference of charge on Cint and the DAC output will be transferred to the ADC (Sigma Delta Integrator).
After the charge transfer to the ADC the steps above will be repeated.
The larger the number the cycles are repeated the larger the signal out of the ADC with improved SNR. The
sensitivity is therefore directly related to the number of cycles.
The SX8661 allows setting the sensitivity for each sensor individually in applications which have a variety of
sensors sizes or different overlays or for fine-tuning performances. The optimal sensitivity is depending heavily on
the final application. If the sensitivity is too low the ticks will not pass the thresholds and touch/proximity detection
will not be possible. In case the sensitivity is set too large, some power will be wasted and false touch/proximity
information may be output (i.e. for touch buttons => finger not touching yet, for proximity sensors => finger/hand
not close enough).
Once the ASI has finished the first sensor, the ticks are stored and the ASI will start measuring the next sensor
until all (enabled) sensors pins have been treated.
In case some sensors are disabled then these result in lower power consumption simply because the ASI is active
for a shorter period and the following processing period will be shorter.
The ticks from the ASI will then be handled by the digital processing.
The ASI will shut down and wait until new sensing period will start.
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3.10 Offset Compensation
The capacitance at the CAP pins is determined by an intrinsic capacitance of the integrated circuit, the PCB
traces, ground coupling and the sensor planes. This capacitance is relatively large and might become easily some
tens of pF. This parasitic capacitance will vary only slowly over time due to environmental changes.
A finger touch is in the order of one pF. If the finger approaches the sensor this occurs typically fast.
The ASI has the difficult task to detect and distinguish a small, fast changing capacitance, from a large, slow
varying capacitance. This would require a very precise, high resolution ADC and complicated, power consuming,
digital processing.
The SX8661 features a 16 bit DAC which compensates for the large, slow varying capacitance already in front of
the ADC. In other words the ADC converts only the desired small signal. In the ideal world the ADC will put out
zero ticks even if the external capacitance is as high as 100pF.
At each power-up of the SX8661 the Digital Compensation Values (DCV) are estimated by the digital processing
algorithms. The algorithm will adjust the compensation values such that zero ticks will be generated by the ADC.
Once the correct compensation values are found these will be stored and used to compensate each CAP pin.
If the SX8661 is shut down the compensation values will be lost. At a next power-up the procedure starts all over
again. This assures that the SX8661 will operate under any condition. Powering up at e.g. different temperatures
will not change the performance of the SX8661 and the host does not have to do anything special.
The DCVs do not need to be updated if the external conditions remain stable.
However if e.g. temperature changes this will influence the external capacitance. The ADC ticks will drift then
slowly around zero values basically because of the mismatch of the compensation circuitry and the external
capacitance.
In case the average value of the ticks become higher than the positive noise threshold (configurable by user) or
lower than the negative threshold (configurable by user) then the SX8661 will initiate a compensation procedure
and find a new set of DCVs.
Compensation procedures can as well be initiated by the SX8661 on periodic intervals. Even if the ticks remain
within the positive and negative noise thresholds the compensation procedure will then estimate new sets of
DCVs.
Finally the host can initiate a compensation procedure by using the I2C interface. This is e.g. required after the
host changed the sensitivity of sensors.
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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.
ASI
processing
SPM
ticks (raw)
tick-diff
low pass
processing
tick-ave
PWM LED
controller
GPIO
controller
I2C
compensation DCV
Figure 19 Processing
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.
Figure 20 Configuration
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.
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In case the application needs different settings than the QSM settings then the SX8661 can be setup and/or
programmed over the I2C interface.
The configuration parameters of the SX8661 can be stored in the Multiple Time Programmable (MTP) Non
Volatile Memory (NVM). The NVM contains all those parameters that are defined and stable for the application.
Examples are the number of sensors enabled, sensitivity, active and Doze scan period. The details of these
parameters are described in the next chapters.
At power up the SX8661 checks if the NVM contains valid data. In that case the configuration parameter source
becomes the NVM. If the NVM is empty or non-valid then the configuration source becomes the QSM. In the next
step the SX8661 copies the configuration parameter source into the Shadow Parameter Memory (SPM). The
SX8661 is operational and uses the configuration parameters of the SPM.
During power down or reset event the SPM loses all content. It will automatically be reloaded following power up
or at the end of the reset event.
The host will interface with the SX8661 through the I2C bus and the analog output interface.
The I2C of the SX8661 consists of 16 registers. Some of these I2C registers are used to read the status and
information of the buttons. Other I2C registers allow the host to take control of the SX8661. The host can e.g.
decide to change the operation mode from active mode to Doze mode or go into sleep (according Figure 9).
Two additional modes allow the host to have an access to the SPM or indirect access to the NVM.
These modes are required during development, can be used in real time or in-field programming.
Figure 21 shows the Host SPM mode. In this mode the host can decide to overwrite the SPM. This is useful
during the development phases of the application where the configuration parameters are not yet fully defined and
as well during the operation of the application if some parameters need small deviations from the QSM or NVM
content.
Figure 21 Host SPM mode
The content of the SPM remains valid as long as the SX8661 is powered. After a power down the host needs to
re-write the SPM at the next power-up.
Figure 22 shows the Host NVM mode. In this mode the host will be able to write the NVM.
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Figure 22 Host NVM mode
The writing of the host towards the NVM is not done directly but done in 2 steps (Figure 22).
In the first step the host writes to the SPM (as in Figure 21). In the second step the host signals the SX8661 to
copy the SPM content into the NVM.
Initially the NVM memory is empty and it is required to determine a valid parameter set for the application. This
can be done during the development phase using dedicated evaluation hardware representing the final
application. This development phase uses probably initially the host SPM mode which allows faster iterations.
Once the parameter set is determined this can be written to the NVM over the I2C using the 2 steps approach by
the host or a dedicated programmer for large volumes production (as described in the paragraphs 6.6 and 6.7).
3.13 Power Management
The SX8661 uses on-chip voltage regulators which are controlled by the on-chip microprocessor. The regulators
need to be stabilized with an external capacitor between VANA and ground and between VDIG and ground (see
Table 5). Both regulators are designed to only drive the SX8661 internal circuitry and must not be loaded
externally.
3.14 Clock Circuitry
The SX8661 has its own internal clock generation circuitry that does not require any external components. The
clock circuitry is optimized for low power operation and is controlled by the on-chip microprocessor. The typical
operating frequency of the oscillating core is 16.7MHz from which all other lower frequencies are derived.
3.15 I2C interface
The I2C interface allows the communication between the host and the SX8661.
The I2C slave implemented on the SX8661 is compliant with the standard (100kb/s) and fast mode (400kb/s)
The default SX8661 I2C address equals 0b010 1011.
A different I2C address can be programmed by the user in the NVM.
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3.16 Interrupt
3.16.1 Power up
During power up the INTB is kept low. Once the power up sequence is terminated the INTB is cleared
autonomously. The SX8661 is then ready for operation. The AOI levels are updated at the latest one scan period
after the rising edge of INTB.
Figure 23 Power Up vs. INTB
During the power on period the SX8661 stabilizes the internal regulators, RC clocks and the firmware initializes all
registers.
During the power up the SX8661 is not accessible and I2C communications are forbidden. The GPIOs set as
inputs with a pull up resistor.
As soon as the INTB rises the SX8661 will be ready for I2C communication. The GPIOs are then configured
according the parameters in the SPM.
The value of INTB before power up depends on the INTB pull up resistor supply voltage.
3.16.2 Assertion
INTB is updated in Active or Doze mode once every scan period.
The INTB will be asserted at the following events:
• if a Button event occurred (touch or release if enabled). I2C register CapStatLsb show the detailed status of
the Buttons,
• when actually entering Active or Doze mode via a host request (may be delayed by 1 scan period). I2C
register CompOpmode shows the current operation mode,
• once compensation procedure is completed either through automatic trigger or via host request (may be
delayed by 1 scan period),
• once SPM write is effective (may be delayed by 1 scan period),
• once NVM burn procedure is completed (may be delayed by 1 scan period),
• during reset (power up, hardware RESETB, software reset).
3.16.3 Clearing
The clearing of the INTB is done as soon as the host performs a read to any of the SX8661 I2C registers.
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3.16.4 Example
A typical example of the assertion and clearing of the INTB and the I2C communication is shown in Figure 24.
Figure 24 Interrupt and I2C
When a button is touched the SX8661 will assert the interrupt (1). The host will read the SX8661 status
information over the I2C (2) and this clears the interrupt.
If the finger releases the button the interrupt will be asserted (3), the host reads the status (4) which clears the
interrupt.
In case the host will not react to an interrupt then this will result in a missing touch.
3.17 Reset
The reset can be performed by 3 sources:
- power up,
- RESETB pin,
- software reset.
3.17.1 Power up
During power up the INTB is kept low. Once the power up sequence is terminated the INTB is released
autonomously. The SX8661 is then ready for operation.
Figure 25 Power Up vs. INTB
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During the power on period the SX8661 stabilizes the internal regulators, RC clocks and the firmware initializes all
registers.
During the power up the SX8661 is not accessible and I2C communications are forbidden.
As soon as the INTB rises the SX8661 will be ready for I2C communication.
3.17.2 RESETB
When RESETB is driven low the SX8661 will reset and start the power up sequence as soon as RESETB is
driven high or pulled high.
In case the user does not require a hardware reset control pin then the RESETB pin can be connected to VDD.
Figure 26 Hardware Reset
3.17.3 Software Reset
To perform a software reset the host needs to write 0xDE followed by 0x00 at the SoftReset register at address
0xB1.
Figure 27 Software Reset
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3.18 General Purpose Input and Outputs
The SX8661 offers eight General Purpose Input and Outputs (GPIO) pins which can be configured in any of these
modes:
- GPP (General Purpose PWM)
- GPO (General Purpose Output)
- SPO (Special Purpose Output)
The input state of the GPIO is only used during the initial phase of the power up period.
Each of these GPIO modes is described in more details in the following sections.
The polarity of the GPP and GPO pins is defined as in figure below, driving an LED as example. It has to be set
accordingly in SPM parameter GpioPolarity.
Figure 28 polarity = 1 (a), polarity = 0 (b)
The PWM blocks used in GPP and GPO modes are 8-bits based and clocked at 2MHz typ. hence offering 256
selectable pulse width values with a granularity of 0.5us typ.
Figure 29 PWM definition, (a) small pulse width, (b) large pulse width
3.18.1 GPP mode
GPIOs configured as GPP will operate as PWM outputs directly controlled by the host. A typical application is
LED dimming.
Typical GPP operation is illustrated in figure below.
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Figure 30 LED control in GPP mode
SPM/I2C parameters applicable in GPP mode are listed in table below. Please refer to the relevant SPM/I2C
parameters sections for more details.
SPM
I2C
GpioMode
GpioOutPwrUp
GpioPolarity
GpioIntensityOn
GpioIntensityOff
GpioFunction
GppPinId
GppIntensity
GPP
X
1
X
X
1
X
1
X
X
X
1
X
1
At power up, GppIntensity of each GPP pin is initialized with GpioIntensityOn or GpioIntensityOff depending on GpioOutPwrUp
corresponding bits value.
Table 9 SPM/I2C Parameters Applicable in GPP Mode
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3.18.2 GPO Dual Reporting
GPIOs configured as GPO will operate as digital outputs which can generate both standard low/high logic levels
and PWM low/high duty cycles levels. Typical application is LED ON/OFF control. This is the dual reporting mode.
The SX8661 offers additionally a triple reporting mode which allows the reporting of proximity by a medium strong
LED intensity (section 3.18.5).
Transitions between ON and OFF states can be triggered either automatically in Autolight mode or manually by
the host. This is illustrated in figures below.
Figure 31 LED Control in GPO mode, Autolight OFF
Figure 32 LED Control in GPO mode, Autolight ON (mapped to Button)
Additionally these transitions can be configured to be done with or without fading following a logarithmic or linear
function. This is illustrated in figures below.
Figure 33 GPO ON transition (LED fade in), normal polarity, (a) linear, (b) logarithmic
Figure 34 GPO ON transition (LED fade in), inverted polarity, (a) linear, (b) logarithmic
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The fading out (e.g. after a button is released) is identical to the fading in but an additional off delay can be added
before the fading starts (Figure 35 and Figure 36).
Figure 35 GPO OFF transition (LED fade out), normal polarity, (a) linear, (b) logarithmic
Figure 36 GPO OFF transition (LED fade out), inverted polarity, (a) linear, (b) logarithmic
Please note that standard high/low logic signals are just a specific case of GPO mode and can also be generated
simply by setting inc/dec time to 0 (i.e. OFF) and programming intensity OFF/ON to 0x00 and 0xFF.
3.18.3 GPO Fading
The SX8661 supports two different fading modes, namely Single and Continuous. These fading modes can be
configured for each GPIO individually. Please see 5.9 “GPIO Parameters” for more information on how to
configure this feature.
i) Single Fading Mode:
The GPO pin fades in when the associated button is touched and it fades out when it is released. This is shown in
Figure 37
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OFF
ON
OFF
DATASHEET
ON intensity
OFF intensity
OFF intensity
fading-in
delay_off
fading-out
Figure 37 Single Fading Mode
ii) Continuous Fading Mode:
The GPO pin fades in and fades out continuously when the associated button is touched. The fading in and out
stops when the button is released. This is shown in Figure 38.
OFF
ON
ON intensity
OFF intensity
OFF intensity
fading-in fading-out
Figure 38 Continuous Fading Mode
3.18.4 Intensity index vs PWM pulse width
Tables below are used to convert all intensity indexes parameters GpioIntensityOff, GpioIntensityOn and
GppIntensity but also to generate fading in GPO mode
During fading in(out), the index is automatically incremented(decremented) at every Inc(Dec)Time x
Inc(Dec)Factor until it reaches the programmed GpioIntensityOn(Off) value.
Index
0
1
2
3
4
5
6
7
8
Lin/Log
0/0
2/0
3/0
4/0
5/0
6/2
7/2
8/2
9/2
Index
32
33
34
35
36
37
38
39
40
Lin/Log
33/5
34/5
35/5
36/5
37/5
38/6
39/6
40/6
41/6
Revision v3.2, January 2011
Index
64
65
66
67
68
69
70
71
72
Lin/Log
65/12
66/13
67/13
68/13
69/14
70/14
71/14
72/15
73/15
Index
96
97
98
99
100
101
102
103
104
Lin/Log
97/26
98/27
99/27
100/28
101/29
102/29
103/30
104/30
105/31
Index
128
129
130
131
132
133
134
135
136
Lin/Log
129/48
130/49
131/50
132/51
133/52
134/53
135/54
136/55
137/55
© 2011 Semtech Corp.
34
Index
160
161
162
163
164
165
166
167
168
Lin/Log
161/81
162/82
163/83
164/84
165/86
166/87
167/88
168/89
169/91
Index
192
193
194
195
196
197
198
199
200
Lin/Log
193/125
194/127
195/129
196/130
197/132
198/133
199/135
200/137
201/139
Index
224
225
226
227
228
229
230
231
232
Lin/Log
225/184
226/186
227/188
228/190
229/192
230/194
231/197
232/199
233/201
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9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
10/2
11/2
12/2
13/2
14/2
15/3
16/3
17/3
18/3
19/3
20/3
21/3
22/3
23/3
24/4
25/4
26/4
27/4
28/4
29/4
30/4
31/4
32/5
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
42/6
43/7
44/7
45/7
46/7
47/7
48/8
49/8
50/8
51/8
52/9
53/9
54/9
55/9
56/10
57/10
58/10
59/10
60/11
61/11
62/11
63/12
64/12
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
74/15
75/16
76/16
77/16
78/17
79/17
80/18
81/18
82/19
83/19
84/20
85/20
86/21
87/21
88/22
89/22
90/23
91/23
92/24
93/24
94/25
95/25
96/26
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
106/32
107/32
108/33
109/33
110/34
111/35
112/35
113/36
114/37
115/38
116/38
117/39
118/40
119/40
120/41
121/42
122/43
123/44
124/44
125/45
126/46
127/47
128/48
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
138/56
139/57
140/58
141/59
142/60
143/61
144/62
145/63
146/64
147/65
148/66
149/67
150/68
151/69
152/71
153/72
154/73
155/74
156/75
157/76
158/77
159/78
160/80
DATASHEET
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
170/92
171/93
172/95
173/96
174/97
175/99
176/100
177/101
178/103
179/104
180/106
181/107
182/109
183/110
184/111
185/113
186/114
187/116
188/117
189/119
190/121
191/122
192/124
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
202/140
203/142
204/144
205/146
206/147
207/149
208/151
209/153
210/155
211/156
212/158
213/160
214/162
215/164
216/166
217/168
218/170
219/172
220/174
221/176
222/178
223/180
224/182
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
234/203
235/205
236/208
237/210
238/212
239/215
240/217
241/219
242/221
243/224
244/226
245/229
246/231
247/233
248/236
249/238
250/241
251/243
252/246
253/248
254/251
255/253
256/256
Lin/Log
64/131
63/129
62/127
61/126
60/124
59/123
58/121
57/119
56/117
55/116
54/114
53/112
52/110
51/109
50/107
49/105
48/103
47/101
46/100
45/98
44/96
43/94
42/92
41/90
40/88
39/86
38/84
37/82
36/80
35/78
34/76
33/74
Index
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
Lin/Log
32/72
31/70
30/68
29/66
28/64
27/62
26/59
25/57
24/55
23/53
22/50
21/48
20/46
19/44
18/41
17/39
16/37
15/35
14/32
13/30
12/27
11/25
10/23
9/20
8/18
7/15
6/13
5/10
4/8
3/5
2/3
0/0
Table 10 Intensity index vs. PWM pulse width (normal polarity)
Index
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Lin/Log
256/256
255/256
254/256
253/256
252/256
251/254
250/254
249/254
248/254
247/254
246/254
245/254
244/254
243/254
242/253
241/253
240/253
239/253
238/253
237/253
236/253
235/253
234/253
233/252
232/252
231/252
230/252
229/252
228/252
227/252
226/252
225/251
Index
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
Lin/Log
224/251
223/251
222/251
221/251
220/251
219/250
218/250
217/250
216/250
215/250
214/249
213/249
212/249
211/249
210/249
209/248
208/248
207/248
206/248
205/247
204/247
203/247
202/247
201/246
200/246
199/246
198/246
197/245
196/245
195/245
194/244
193/244
Index
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
Lin/Log
192/244
191/243
190/243
189/243
188/242
187/242
186/242
185/241
184/241
183/241
182/240
181/240
180/240
179/239
178/239
177/238
176/238
175/237
174/237
173/236
172/236
171/235
170/235
169/234
168/234
167/233
166/233
165/232
164/232
163/231
162/231
161/230
Index
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
Lin/Log
160/230
159/229
158/229
157/228
156/227
155/227
154/226
153/226
152/225
151/224
150/224
149/223
148/223
147/222
146/221
145/221
144/220
143/219
142/218
141/218
140/217
139/216
138/216
137/215
136/214
135/213
134/212
133/212
132/211
131/210
130/209
129/208
Index
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
Lin/Log
128/208
127/207
126/206
125/205
124/204
123/203
122/202
121/201
120/201
119/200
118/199
117/198
116/197
115/196
114/195
113/194
112/193
111/192
110/191
109/190
108/189
107/188
106/187
105/185
104/184
103/183
102/182
101/181
100/180
99/179
98/178
97/176
Index
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
Lin/Log
96/175
95/174
94/173
93/172
92/170
91/169
90/168
89/167
88/165
87/164
86/163
85/161
84/160
83/159
82/157
81/156
80/155
79/153
78/152
77/150
76/149
75/147
74/146
73/145
72/143
71/142
70/140
69/139
68/137
67/135
66/134
65/132
Index
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
Table 11 Intensity index vs. PWM pulse width (inverted polarity)
Recommended/default settings are inverted polarity (to take advantage from high sink current capability) and
logarithmic mode (due to the non-linear response of the human eye).
3.18.5 GPO Triple Reporting
The button information touch and release can be reported on the LEDs in dual mode (ON and OFF).
The proximity information can be shown using the dual mode by attributing a dedicated LED to the proximity
sensor. The LED will show then proximity detected or no proximity detected. The fading principles are equal to the
fading of sensors defined as buttons as described in the previous sections.
In triple mode proximity is reported on all LEDs by an intermediate LED intensity.
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Figure 39 LEDs in triple reporting mode proximity
Figure 39 shows an example of proximity detection and the reporting on LEDs. As soon as proximity is detected
all LEDs (2 LEDs are shown for simplicity) will fade in and stop at the proximity intensity level. In case proximity is
not detected anymore then the LEDs remain at the proximity intensity for a configurable time and then the fading
out will start.
Figure 40 LEDs in triple reporting mode proximity and touch
Figure 40 shows an example of proximity detection followed by a rapid touch on the sensor sd1.
The LEDs d1 and d2 will fade in as soon as proximity is detected (using the Inc_Prox parameter).
As soon as the finger touches the sensor sd1 the fading in of d1 will go to the ON intensity (using the touch
increment parameter).
The LED d2 remains at the proximity intensity level as sensors sd2 is not touched.
If the finger is removed rapidly the fading out of d1 will first use the touch decrement parameter to the proximity
intensity level. If the finger leaves the proximity region d1 and 2 will fade out simultaneously using the proximity
delay and decrement parameters.
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4 PIN DESCRIPTIONS
4.1
Introduction
This chapter describes briefly the pins of the SX8661, the way the pins are protected, if the pins are analog,
digital, require pull up or pull down resistors and show control signals if these are available.
4.2
ASI pins
CAP0, CAP1,...,CAP7
The capacitance sensor pins (CAP0, CAP1,...,CAP7) are connected directly to the ASI circuitry which converts
the sensed capacitance into digital values.
The capacitance sensor pins which are not used should be left open.
The enabled CAP pins need be connected directly to the sensors without significant resistance (typical below
some ohms, connection vias are allowed).
The capacitance sensor pins are protected to VANA and GROUND.
Figure 41 shows the simplified diagram of the CAP0, CAP1,...CAP7 pins.
SX8661
VANA
sensor
CAPx
CAP_INx
ASI
Note : x = 0, 1,2,…7
Figure 41 Simplified diagram of CAP0, CAP1,...,CAP7
CN, CP
The CN and the CP pins are connected to the ASI circuitry. A 1nF sampling capacitor between CP and CN needs
to be placed as close as possible to the SX8661.
The CN and CP are protected to VANA and GROUND.
Figure 42 shows the simplified diagram of the CN and CP pins.
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VANA
CP
ASI
VANA
CN
Figure 42 Simplified diagram of CN and CP
4.3
Host interface pins
The host interface consists of the interrupt pin INTB, a reset pin RESETB and the standard I2C pins: SCL and
SDA.
INTB
The INTB pin is an open drain output that requires an external pull-up resistor (1..10 kOhm). The INTB pin is
protected to VDD using dedicated devices. The INTB pin has diode protected to GROUND.
Figure 43 shows a simplified diagram of the INTB pin.
VDD
SX8661
R_INT
INTB
to host
INT
Figure 43 Simplified diagram of INTB
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SCL
The SCL pin is a high impedance input pin. The SCL pin is protected to VDD, using dedicated devices, in order to
conform to standard I2C slave specifications. The SCL pin has diode protected to GROUND.
An external pull-up resistor (1..10 kOhm) is required on this pin.
Figure 44 shows the simplified diagram of the SCL pin.
VDD
SX8661
R_SCL
SCL
SCL_IN
from host
Figure 44 Simplified diagram of SCL
SDA
SDA is an IO pin that can be used as an open drain output pin with external pull-up resistor or as a high
impedance input pin. The SDA IO pin is protected to VDD, using dedicated devices, in order to conform to
standard I2C slave specifications. The SDA pin has diode protected to GROUND.
An external pull-up resistor (1..10 kOhm) is required on this pin.
Figure 45 shows the simplified diagram of the SDA pin.
VDD
SX8661
R_SDA
SDA
SDA_IN
from/to host
SDA_OUT
Figure 45 Simplified diagram of SDA
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DATASHEET
RESETB
The RESETB pin is a high impedance input pin. The RESETB pin is protected to VDD using dedicated devices.
The RESETB pin has diode protected to GROUND.
Figure 46 shows the simplified diagram of the RESETB pin controlled by the host.
VDD
SX8661
R_RESETB
RESETB
RESETB_IN
from host
Figure 46 Simplified diagram of RESETB controlled by host
Figure 47 shows the RESETB without host control.
VDD
SX8661
RESETB
RESETB_IN
Figure 47 Simplified diagram of RESETB without host control
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4.4
DATASHEET
Power management pins
The power management pins consist of the Power, Ground and Regulator pins.
VDD
VDD is a power pin and is the main power supply for the SX8661.
VDD has protection to GROUND.
Figure 48 shows a simplified diagram of the VDD pin.
SX8661
VDD
VDD
Figure 48 Simplified diagram of VDD
GND
The SX8661 has four ground pins all named GND. These pins and the package center pad need to be connected
to ground potential.
The GND has protection to VDD.
Figure 49 shows a simplified diagram of the GND pin.
SX8661
VDD
GND
GND
Figure 49 Simplified diagram of GND
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VANA, VDIG
The SX8661 has on-chip regulators for internal use (pins VANA and VDIG).
VANA and VDIG have protection to VDD and to GND.
The output of the regulators needs to be de-coupled with a small 100nF capacitor to ground.
Figure 50 shows a simplified diagram of the VANA and VDIG pin.
SX8661
VDD
VDIG
VDIG
Cvdig
GND
VDD
VANA
VANA
Cvana
GND
Figure 50 Simplified diagram of VANA and VDIG
4.5
General purpose IO pins
The SX8661 has 8 General purpose input/output (GPIO) pins.
All the GPIO pins have protection to VDD and GND.
The GPIO pins can be configured as GPO, SPO or GPP.
Figure 51 shows a simplified diagram of the GPIO pins.
Figure 51 Simplified diagram of GPIO pins
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DATASHEET
5 DETAILED CONFIGURATION DESCRIPTIONS
5.1
Introduction
The SX8661 configuration parameters are taken from the QSM or the NVM and loaded into the SPM as explained
in the chapter ‘functional description’.
This chapter describes the details of the configuration parameters of the SX8661.
The SPM is split by functionality into 5 configuration sections:
• General section: operating modes,
• Capacitive Sensors section: related to lower level capacitive sensing,
• Proximity: defining parameters related to proximity sensing
• Button: related to the conversion from sensor data towards button information,
• AOI: defining parameters for the AOI
• Buzzer: defining parameters for the AOI
• Mapping: related to mapping of button information towards GPIO pins,
• GPIO: related to the setup of the GPIO pins.
The total address space of the SPM and the NVM is 128 bytes, from address 0x00 to address 0x7F.
Two types of memory addresses, data are accessible to the user.
• ‘application data’: Application dependent data that need to be configured by the user.
• ‘reserved’: Data that need to be maintained by the user to the QSM default values (i.e. when NVM is burned).
The Table 12 and Table 13 resume the complete SPM address space and show the ‘application data’ and
‘reserved’ addresses, the functional split and the default values (loaded from the QSM).
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DATASHEET
Address
Name
default
QSM value
Address
Name
default
QSM value
0x00
Reserved
0xxx
0x20
ProxReporting
0x7F
0x01
Reserved
0xxx
0x21
ProxIntensity
0x64
0x02
Reserved
0x41
0x22
BtnCfg
0x70
0x03
Reserved
0xxx
0x23
BtnAvgThresh
0x50
0x2B
0x24
BtnCompNegThresh
0xA0
ActiveScanPeriod
0x02
0x25
BtnCompNegCntMax
0x01
DozeScanPeriod
0x0D
0x26
BtnHysteresis
0x0A
PassiveTimer
0x00
0x27
BtnStuckAtTimeout
0x00
0x06
0x07
Button
I2CAddress
0x05
General
0x04
0x00
0x28
BtnStrongestHysteresis
0x80
CapModeMisc
0x04
0x29
BtnLongPressTimer
0x00
0x0A
Reserved
0x00
0x2A
Reserved
0xFF
0x0B
CapMode7_4
0x55
0x2B
AoiCfg
0x01
0x0C
CapMode3_0
0x57
0x2C
AoiBtnMapMsb
0x55
0x0D
CapSensitivity0_1
0x72
0x2D
AoiBtnMapLsb
0x55
0x0E
CapSensitivity2_3
0x22
0x2E
AoiLevelBtn0
0xFF
0x0F
CapSensitivity4_5
0x22
0x2F
AoiLevelBtn1
0x2E
CapSensitivity6_7
0x22
0x30
AoiLevelBtn2
0x45
Reserved
0x00
0x31
AoiLevelBtn3
0x5D
Reserved
0x00
0x32
AoiLevelBtn4
0x74
CapThresh0
0xA0
0x33
AoiLevelBtn5
0x8B
AoiLevelBtn6
0xA3
AoiLevelBtn7
0xBA
0x10
0x11
0x12
0x13
Analog Output Interface (AOI)
Reserved
0x09
Capacitive Sensors
0x08
0x34
0xA0
0x35
0x16
CapThresh3
0xA0
0x36
AoiLevelIdle
0xFF
0x17
CapThresh4
0xA0
0x37
BuzzerCfg
0xA4
0x18
CapThresh5
0xA0
0x38
BuzzerFreqPhase1
0x40
0x19
CapThresh6
0xA0
0x39
BuzzerFreqPhase2
0x20
0x1A
CapThresh7
0xA0
0x3A
Reserved
0x00
0x1B
CapPerComp
0x00
0x3B
MapAutoLight0
0x07
0x1C
ProxIncDecTime
0x14
0x3C
MapAutoLight1
0x65
ProxCfg
0xB0
0x3D
MapAutoLight2
0x43
ProxDebounce
0x00
0x3E
MapAutoLight3
0x21
ProxHysteresis
0x0A
0x3F
MapAutoLightGrp0Msb
0x00
0x1D
0x1E
0x1F
Mapping
0x15
Buzzer
0xA0
CapThresh2
0x14
Proximity
CapThresh1
Table 12 SPM address map: 0x00…0x3F
Note
• ‘0xxx’:
write protected data
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0x40
0x41
0x42
Name
Mapping
Address
DATASHEET
default QSM
value
Address
Name
default QSM
value
MapAutoLightGrp0Lsb
0x00
0x60
GpioDecTime7_6
0x44
MapAutoLightGrp1Msb
0x00
0x61
GpioDecTime5_4
0x44
MapAutoLightGrp1Lsb
0x00
0x62
GpioDecTime3_2
0x44
0xC0
0x63
GpioDecTime1_0
0x44
GpioMode3_0
0x00
0x64
GpioOffDelay7_6
0x00
0x45
GpioIntensityOn0
0xFF
0x65
GpioOffDelay5_4
0x00
0x46
GpioIntensityOn1
0xFF
0x66
GpioOffDelay3_2
0x00
0x47
GpioIntensityOn2
0xFF
0x67
GpioOffDelay1_0
0x00
0x48
GpioIntensityOn3
0xFF
0x68
GpioPullUpDown7_4
0x00
0x49
GpioIntensityOn4
0xFF
0x69
GpioPullUpDown3_0
0x00
0x4A
GpioIntensityOn5
0xFF
0x6A
Reserved
0x00
0x4B
GpioIntensityOn6
0xFF
0x6B
Reserved
0x00
0x4C
GpioIntensityOn7
0xFF
0x6C
Reserved
0x00
0x4D
GpioIntensityOff0
0x00
0x6D
GpioFadingMode7_4
0x00
0x4E
GpioIntensityOff1
0x00
0x6E
GpioFadingMode3_0
0x00
0x4F
GpioIntensityOff2
0x00
0x6F
Reserved
0x50
0x50
GpioIntensityOff3
0x00
0x70
CapProxEnable
0x74
GpioIntensityOff4
0x00
0x71
Reserved
0x10
0x51
Gpio
GpioMode7_4
0x44
Gpio
0x43
GpioIntensityOff5
0x00
0x72
Reserved
0x45
0x53
GpioIntensityOff6
0x00
0x73
Reserved
0x03
0x54
GpioIntensityOff7
0x00
0x74
Reserved
0xFF
0x55
Reserved
0xFF
0x75
Reserved
0xFF
0x56
GpioOutPwrUp
0x00
0x76
Reserved
0xFF
0x57
GpioAutoLight
0xFF
0x77
Reserved
0xD5
0x58
GpoPolarity
0x80
0x78
Reserved
0x55
0x59
GpioFunction
0x80
0x79
Reserved
0x55
0x5A
GpioIncFactor
0x00
0x7A
Reserved
0x7F
0x5B
GpioDecFactor
0x00
0x7B
Reserved
0x23
0x5C
GpioIncTime7_6
0x11
0x7C
Reserved
0x22
0x5D
GpioIncTime5_4
0x11
0x7D
Reserved
0x41
0x5E
GpioIncTime3_2
0x11
0x7E
Reserved
0xFF
0x5F
GpioIncTime1_0
0x11
0x7F
SpmCrc
0x52
1
0x3F
Table 13 SPM address map: 0x40…0x7F
1
Note
• SpmCrc:
CRC depending on SPM content, updated in Active or Doze mode.
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5.2
DATASHEET
General Parameters
General Parameters
Address
Name
Bits
Description
0x04
I2CAddress
7
Reserved (0x00).
6:0
Defines the I2C address.
The I2C address will be active after a reset.
Default: 0x2B
0x05
ActiveScanPeriod 7:0
Defines Active Mode Scan Period (Figure 8).
0x00: Reserved
0x01: 15ms
0x02: 30ms
…
0xFF: 255 x 15ms
Default: 0x02
0x06
DozeScanPeriod
7:0
Defines Doze Mode Scan Period (Figure 8).
0x00: Reserved
0x01: 15ms
…
0x0D: 195ms
…
0xFF: 255 x 15ms
Default: 0x0D
0x07
PassiveTimer
7:0
Defines Passive Timer on Button Information (Figure 9).
0x00: OFF
0x01: 1 second
…
0xFF: 255 seconds
Default: 0x00
0x08
Reserved
7:0
Reserved (0x00)
Table 14 General Parameters
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5.3
DATASHEET
Capacitive Sensors Parameters
Capacitive Sensors Parameters
Address
Name
Bits Description
0x09
CapModeMisc
7:3 Reserved (0x00)
2:0 IndividualSensitivity Defines common sensitivity for all sensors or individual sensor
sensitivity.
000: Common sensitivity settings (CapSensitivity0_1[7:4])
100: Individual sensitivity settings (CapSensitivityx_x) (default)
Else : Reserved
0x0A
Reserved
7:0 Reserved (0x00)
0x0B
CapMode7_4
7:6 CAP7 Mode
Default Button
1:0 CAP4 Mode
Defines the mode of the CAP pin.
00: Disabled
01: Button
10: Reserved
11: Proximity (CAP0),
Reserved (CAP6,..CAP1)
7:6 CAP3 Mode
Default: 0x5557
Default Button
5:4 CAP6 Mode
3:2 CAP5 Mode
0x0C
CapMode3_0
0x0D
CapSensitivity0_1
0x0E
CapSensitivity2_3
0x0F
CapSensitivity4_5
CapSensitivity6_7
Default Button
Default Button
5:4 CAP2 Mode
Default Button
3:2 CAP1 Mode
Default Button
1:0 CAP0 Mode
Default Proximity
7:4 CAP0 Sensitivity - Common Sensitivity Defines the sensitivity.
0x0: Minimum
3:0 CAP1 Sensitivity
0x1: 1
…
7:4 CAP2 Sensitivity
0x7: Maximum
3:0 CAP3 Sensitivity
0x8..0xF: Reserved
7:4 CAP4 Sensitivity
3:0 CAP5 Sensitivity
0x10
Default Button
7:4 CAP6 Sensitivity
Default CapSensitivity0_1: 0x72
Default CapSensitivity2_3: 0x22
Default CapSensitivity4_5: 0x22
Default CapSensitivity6_7: 0x22
3:0 CAP7 Sensitivity
0x11
Reserved
7:0 Reserved (0x00)
0x12
Reserved
7:0 Reserved (0x00)
0x13
CapThresh0
7:0 CAP0 Touch Threshold
0x14
CapThresh1
7:0 CAP1 Touch Threshold
0x15
CapThresh2
7:0 CAP2 Touch Threshold
0x16
CapThresh3
7:0 CAP3 Touch Threshold
0x17
CapThresh4
7:0 CAP4 Touch Threshold
0x18
CapThresh5
7:0 CAP5 Touch Threshold
0x19
CapThresh6
7:0 CAP6 Touch Threshold
0x1A
CapThresh7
7:0 CAP7 Touch Threshold
0x1B
CapPerComp
7:4 Reserved (0x00)
3:0 Periodic Offset Compensation
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Defines the Touch Threshold ticks.
0x00: 0,
0x01: 4,
…
0xA0: 640 (default),
…
0xFF: 1020
Defines the periodic offset compensation.
0x0: OFF (default)
0x1: 1 second
0x2: 2 seconds
…
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Capacitive Sensors Parameters
Address
Name
Bits Description
0x7: 7 seconds
0x8: 16 seconds
0x9: 18 seconds
…
0xE: 28 seconds
0xF: 60 seconds
0x70
CapProxEnable
7:0 Enables proximity sensing.
0x46: OFF
0x74: ON (default)
Table 15 Capacitive Sensors Parameters
CapModeMisc:
By default the ASI is using an individual sensitivity for each CAP pin (with proximity sensor set to maximum
sensitivity while touch sensors are set to a lower one). The individual sensitivity mode results in longer sensing
periods than required in common sensitivity mode.
The ASI can use common sensitivity for all capacitive sensors in the case overlay material and sensors sizes
are about equal. The register bits CapSensitivity0_1[7:4] determine the sensitivity for all sensors in common
sensitivity mode.
CapMode7_4, CapMode3_0:
The CAP7 to CAP0 pins can be set as a button or disabled depending on the application.
CAP0 can be used for proximity sensing (additionally set register CapProxEnable).
Buttons
minimum
maximum
zero
seven
Table 16 Number of buttons (with CAP0 = proximity)
Buttons
minimum
maximum
one
eight
Table 17 Number of buttons (with CAP0 = button or disabled)
Buttons and disabled CAP pins can be attributed freely (examples in Figure 52).
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Figure 52 Button examples
CapSensitivity0_1, CapSensitivity2_3, CapSensitivity4_5, CapSensitivity6_7, CapProxEnable:
The sensitivity of the sensors can be set between 8 values. The higher the sensitivity is set the larger the value
of the ticks will be.
The minimum sensitivity can be used for thin overlay materials and large sensors, while the maximum
sensitivity is required for thicker overlay and smaller sensors or proximity sensing.
The required sensitivity needs to be determined during a product development phase. Too low sensitivity
settings result in missing touches. Too high sensitivity settings will result in fault detection of fingers hovering
above the touch sensors.
The sensitivity is identical for all sensors in common sensitivity mode using the bits CapSensitivity0_1[7:4] and
can be set individually using register CapModeMisc[2:0].
The maximum number of ticks that can be obtained depends on the selected sensitivity and if proximity sensing is
enabled. This is illustrated in Table 18.
Sensitivity
Approximate
Maximum Tick Level
(CapProxEnable = OFF)
Approximate
Maximum Tick Level
(CapProxEnable = ON)
0
1000
4000
1
2000
8000
2
3000
12000
3
4000
16000
4
5000
20000
5
6000
24000
6
7000
28000
7
8000
32000
Table 18 ASI Maximum Tick Levels
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CapThresh0, CapThresh1, CapThresh2, CapThresh3, CapThresh4, CapThresh5, CapThresh6, CapThresh7:
For each CAP pin a threshold level can be set individually.
The threshold levels are used by the SX8661 for making touch and release decisions.
The details are explained in the sections for buttons.
CapPerComp:
The SX8661 offers a periodic offset compensation for applications which are subject to substantial
environmental changes. The periodic offset compensation is done at a defined interval and only if buttons are
released.
CapProxEnable:
The SX8661 is intended to be used with proximity. This register is set by default to ON (0x74). In case
proximity is not required then this register should be set to OFF (0x46) and CAP0 Mode should be set to button
or disabled.
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5.4
DATASHEET
Proximity Parameters
Proximity Parameters
Address
Name
Bits
Description
0x1C
ProxIncDecTime
7:4
Defines the time between each increment.
0x0: instantaneous
0x1: 0.5ms (default)
0x2: 1ms
…
0xF: 7.5ms
3:0
Defines the time between each decrement.
0x0: instantaneous
0x1: 0.5ms
0x2: 1ms
…
0x4: 2ms (default)
…
0xF: 7.5ms
7:4
Defines the delay between release and start of fading out.
0x0: instantaneous
0x1: 200 ms
0x2: 400 ms
0x3: 600ms
…
0xA: 2s
0xB: 4s (default)
…
0xF: 12s
3:2
Reserved (0x00)
1
Defines the fading increment factor.
0: intensity index incremented every increment time (default)
1: intensity index incremented every 16 increment times
0
Defines the fading decrement factor.
0: intensity index decremented every decrement time (default)
1: intensity index decremented every 16 decrement times
7:4
Reserved (0x00)
3:2
Defines the number of samples at the scan period for determining proximity release.
00 : no debounce, use incoming sample (default)
01 : 2 samples debounce
10 : 3 samples debounce
11 : 4 samples debounce
1:0
Defines the number of samples at the scan period for determining proximity detection.
00 : no debounce, use incoming sample (default)
01 : 2 samples debounce
10 : 3 samples debounce
11 : 4 samples debounce
7:0
Defines the proximity hysteresis corresponding to a percentage of the CAP0 threshold
(defined in Table 15).
0x00: 0%
0x01: 1%
…
0x0A: 10% (default)
…
0x64: 100%
0x1D
0x1E
0x1F
ProxCfg
ProxDebounce
ProxHysteresis
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Proximity Parameters
Address
Name
Bits
Description
0x20
ProxReporting
7:0
Defines triple or dual mode reporting of proximity on the GPIOs.
0x00: dual mode
0x7F: triple mode (default)
0x21
ProxIntensity
7:0
Defines the proximity ON intensity index.
0x00: 0
0x01: 1
…
0x64: 100 (default)
…
0xFF: 255
Table 19 Proximity Parameters
ProxDebounce
Defines the number of samples for determining proximity detection or out of proximity detection.
This parameter allows to set the debouncer of the proximity differently from the buttons debouncer.
ProxHysteresis
Proximity is detected if the ticks are getting larger as the value defined by:
CapThreshold0 + CapThreshold0 * hysteresis.
Out of proximity is detected if the ticks are getting smaller as the value defined by:
CapThreshold0 – CapThreshold0 * hysteresis.
ProxReporting
Defines the reporting mode of proximity (either dual or triple) on the GPIOs.
ProxIntensity
Defines the proximity intensity index (applicable in triple reporting mode).
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5.5
DATASHEET
Button Parameters
Button Parameters
Address
Name
Bits Description
0x22
BtnCfg
7:6 Defines the buttons and proximity events reporting method on I2C, AOI, GPO,
Buzzer (see Table 21 for details).
00: All
01: Single (default)
10: Strongest
11: Reserved
5:4 Defines the buttons interrupt (for all buttons and proximity).
00 : Interrupts masked
01 : Triggered on Touch
10 : Triggered on Release
11 : Triggered on Touch and Release (default)
3
Defines the number of samples at the scan period for determining a release of a
button.
00 : no debounce, use incoming sample (default)
01 : 2 samples debounce
10 : 3 samples debounce
11 : 4 samples debounce
2:0 Defines the number of samples at the scan period for determining a touch of a
button.
00 : no debounce, use incoming sample (default)
01 : 2 samples debounce
10 : 3 samples debounce
11 : 4 samples debounce
0x23
BtnAvgThresh
7:0 Defines the positive threshold for disabling the processing filter averaging (one
value for all buttons and proximity).
If ticks are above the threshold, then the averaging is suspended.
0x00: 0
0x01: 4
…
0x50: 320 (default)
…
0xFF: 1020
0x24
BtnCompNegThresh
7:0 Defines the negative offset compensation threshold (one value for all buttons and
proximity).
0x00: 0
0x01: 4
…
0xA0: 640 (default)
…
0xFF: 1020
0x25
BtnCompNegCntMax
7:0 Defines the number of ticks (below the negative offset compensation threshold)
which will initiate an offset compensation (one value for all buttons and proximity).
0x00: reserved
0x01: 1 sample (default)
…
0xFF: 255 samples
0x26
BtnHysteresis
7:0 Defines the button hysteresis corresponding to a percentage of the CAP
thresholds (defined in Table 15).
All buttons use the same hysteresis.
0x00: 0%
0x01: 1%
…
0x0A: 10% (default)
…
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DATASHEET
Button Parameters
Address
Name
Bits Description
0x64: 100%
0x27
BtnStuckAtTimeout
7:0 Defines the stuck at timeout for buttons and proximity.
0x00: OFF (default)
0x01: 1 second
…
0xFF: 255 seconds
0x28
BtnStrongestHysteresis
7:0 Defines the hysteresis value for the strongest button filtering engine. This
parameter is only valid when BtnCfg has been configured to “report the strongest
touch”. The proximity sensor is excluded.
The hysteresis element eliminates the jittery output due to environmental noise
when two CAP sensors (configured as buttons) have values very close to each
other. The BtnStrongestHysteresis defines how much bigger the signal of the
second sensor needs to be compared to the strongest detected sensor, before the
second sensor becomes the strongest detected touch.
0x00: 0
0x01: 1
…
0x80: 128 (default)
…
0xFF: 255
0x29
BtnLongPressTimer
7:0 Defines the long press button timeout on AOI pins (applicable in Single Reporting
Mode). The proximity sensor does not trigger the timer.
0x00: OFF (default)
0x01: 1 second
…
0xFF: 255 seconds
Table 20 Button Parameters
The buttons and the proximity sensor operate in a similar way although some parameters can be set uniquely for
buttons or the proximity sensor only (according the previous tables describing the button and proximity
parameters).
A reliable button operation requires a coherent setting of the registers.
Figure 53 shows an example of a touch and a release. The ticks will vary slightly around the zero idle state.
When the touch occurs the ticks will rise sharply. At the release of the button the ticks will go down rapidly and
converge to the idle zero value.
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DATASHEET
ticks_diff
ADVANCED COMMUNICATIONS & SENSING
Figure 53 Touch and Release Example
As soon as the ticks become larger than the CAP thresholds (see registers of the previous section) plus the
hysteresis (defined in register BtnHysteresis ) the debounce counter starts.
In the example of Figure 53 the touch is validated after 2 ticks (BtnCfg [2:0] = 1).
The release is detected immediately (BtnCfg [3] = 0) at the first tick which is below the threshold minus the
hysteresis.
BtnCfg
The SX8661 button and proximity interface has three modes of operation:
• Report All: reports all touches of multiple fingers and proximity detection.
• Report Single: reports only a single touch and/or proximity. Subsequent touches are ignored until the
first touch is released. On the AOI proximity is implicit in case of a button touch.
• Report Strongest: reports the strongest touch. When the signal from another sensor rises above the
first sensor’s signal, the second sensor is then reported instead. On the AOI proximity is implicit in
case of a button touch.
Table 21 resumes the relation of reporting modes and information on the interfaces.
Reporting
Mode
I2C
AOI
GPIOs (LEDs)
Buzzer
All
Buttons and Proximity
Forced to Idle
Buttons and
Proximity
Button
Single
Proximity or
1 Button and Proximity
Idle or 1 Button or
Proximity
Buttons and
Proximity
Button
Strongest
Proximity or
1 Button and Proximity
Idle or 1 Button or
Proximity
Buttons and
Proximity
Button
Table 21 Reporting modes
The user can select to have the interrupt signal (INTB) on touching a button (proximity detected), releasing a
button (out of proximity) or both.
In noisy environments it may be required to debounce the touch and release detection decision.
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DATASHEET
In case the debounce is enabled the SX8661 will count up to the number of debounce samples BtnCfg [1:0],
BtnCfg [3:2] before taking a touch or release decision. The sample period is identical to the scan period.
BtnAvgPosThresh
Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.
In case the ticks get slightly positive this is considered as normal operation. Very large positive tick values
indicate a valid touch. The averaging filter is disabled as soon as the average reaches the value defined by
BtnAvgPosThresh. This mechanism avoids that a valid touch will be averaged and finally the tick difference
becomes zero.
In case three or more sensors reach the BtnAvgPosThresh value simultaneously then the SX8661 will start an
offset compensation procedure.
ticks_diff
Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.
In case the ticks get slightly negative this is considered as normal operation. However large negative values will
trigger an offset compensation phase and a new set of DCVs will be obtained.
The decision to trigger a compensation phase based on negative ticks is determined by the value in the register
BtnCompNegThresh and by the number of ticks below the negative thresholds defined in register
BtnCompNegCntMax. An example is shown in Figure 54.
Figure 54 Negative Ticks Offset Compensation Trigger
BtnCompNegThresh
Small negative ticks are considered as normal operation and will occur very often.
Larger negative ticks however need to be avoided and a convenient method is to trigger an offset
compensation phase. The new set of DCV will assure the idle ticks will be close to zero again.
A trade-off has to be found for the value of this register. A negative threshold too close to zero will trigger a
compensation phase very often. A very negative threshold will never trigger.
BtnCompNegCntMax
As soon as the ticks get smaller than the Negative Threshold the Negative Counter starts to count.
If the counter goes beyond the Negative Counter Max then the offset compensation phase is triggered.
The recommended value for this register is ‘1’ which means that the offset compensation starts on the first tick
below the negative threshold.
BtnHysteresis
The hysteresis percentage is identical for all buttons.
A touch is detected if the ticks are getting larger as the value defined by:
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DATASHEET
CapThreshold + CapThreshold * hysteresis.
A release is detected if the ticks are getting smaller as the value defined by:
CapThreshold - CapThreshold * hysteresis.
BtnStuckAtTimeout
The stuckat timer can avoid sticky buttons.
If the stuckat timer is set to one second then the touch of a finger will last only for one second and then a
compensation will be performed and button hence considered released, even if the finger remains on the
button for a longer time. After the actual finger release the button can be touched again and will be reported as
usual.
In case the stuckat timer is not required it can be set to zero.
BtnStrongestHysteresis
This parameter defines the hysteresis value for the adjacent button filtering engine. This parameter is only
valid when BtnCfg has been configured to report the strongest touch.
When the SX8661 device has been configured to report the strongest touch, a situation may arise where the
CAP signals of two sensors are of approximately equal value. Environmental noise can cause the signals of
these two sensors to fluctuate as shown in Figure 55 (b).
(a)
(b)
CAP1
CAP0
Strongest
Hysteresis
Fluctuation
Figure 55 Strongest touch and Hysteresis
As a result of that, the output of the SX8661 device would also change very quickly as each of the two sensors
becomes the sensor with the strongest touch value. To eliminate this jitter, the SX8661 device adds a
hysteresis element to the calculation of the strongest touch sensor. In that respect, the strongest CAP sensor
is calculated as the sensor whose value is greater that the second detected strongest CAP sensor by the
Strongest hysteresis amount.
For example, as shown in Figure 55, the strongest CAP sensor is initially CAP0 (Figure 55 (b)). CAP1
becomes the strongest detected touch only if at some point in time the following holds true:
CAP1 signal = CAP0 signal + StrongestHysteresis
Similarly, if CAP2 is now also touched, it will only become the strongest detected touch if:
CAP2 signal = CAP1 signal + StrongestHysteresis.
BtnLongPressTimer
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DATASHEET
This timer defines the time in seconds that the AOI will put out a voltage level corresponding to the button
touched. The timer is applicable in the Single Reporting Mode. After the timer expires the AOI will return to the
idle level even if the button is still touched.
The I2C status and GPO are not affected by this timer (i.e. they will be updated when the button is actually
released).
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5.6
DATASHEET
Analog Output Interface Parameters
Analog Output Interface (AOI) Parameters
Address
Name
Bits
Description
0x2B
AoiCfg
7:6
Reserved (0x00).
5:4
Defines AoiLevelDuringBuzzer (same for A&B).
0x00: AOI button level (default)
0x01: AOI Idle level
0x10: min level (0V)
0x11: max level( VDD)
3
Defines Aoi pwm period (same for A&B).
0: 0xFF (255) (default)
1: 0x3F (63)
2:0
Reserved (0x01)
7:0
Button[7]
0x2C
AoiBtnMapMsb
Button[6]
Button[5]
Button[4]
0x2D
AoiBtnMapLsb
7:0
Button[3]
Button[2]
Maps a button touch to one of the two Analog Output
Interfaces (AOI-A / AOI-B), or both.
00 : None
01 : AOI-A (GPIO7)
10 : AOI-B (GPIO6)
11 : Both
Default: 0x5555, i.e. Btn[7..0] mapped on AOI-A
Button[1]
Button[0] or Proximity
0x2E
AoiLevelBtn0
7:0
0x2F
AoiLevelBtn1
7:0
0x30
AoiLevelBtn2
7:0
0x31
AoiLevelBtn3
7:0
0x32
AoiLevelBtn4
7:0
0x33
AoiLevelBtn5
7:0
0x34
AoiLevelBtn6
7:0
0x35
AoiLevelBtn7
7:0
0x36
AoiLevelIdle
7:0
Defines the level index (cf Table 8) for Buttons, Idle or Proximity (for CAP0)
The level index should be smaller or equal to Aoi pwm period as defined in
AoiCfg[3].
0x00: 0
0x01: 1
…
0xFF: 255
Default AoiLevelBtn0: 0xFF
Default AoiLevelBtn1: 0x2E
Default AoiLevelBtn2: 0x45
Default AoiLevelBtn3: 0x5D
Default AoiLevelBtn4: 0x74
Default AoiLevelBtn5: 0x8B
Default AoiLevelBtn6: 0xA3
Default AoiLevelBtn7: 0xBA
Default AoiLevelIdle: 0xFF.
Table 22 AOI Parameters
AoiBtnMap
This register is used to map the available buttons to SWI-A, AOI-B or both. For example, to map buttons 0 to 3
and buttons 4 to 7 on AOI-B, write the following value to the AoiPwmBtnMap register
AoiCfg = 0xAA55;
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AoiLevelBtn0, AoiLevelBtn1,
AoiLevelBtn7, AoiLevelIdle
AoiLevelBtn2,
AoiLevelBtn3,
AoiLevelBtn4,
DATASHEET
AoiLevelBtn5,
AoiLevelBtn6,
These registers define the level that will be output on AOI-A or AOI-B (depending on button mapping) when the
corresponding button is touched or when the corresponding state is active or idle. The duty cycle is defined as
a number of steps.
The mean voltage of a PWM signal is given by:
Mean voltage ≈ (AoiLevelBtnx / AoiPmwPeriod) * Maximum Voltage (VDD)
or:
AoiLevelBtnx ≈ (Mean voltage / Maximum Voltage (VDD)) * AoiPmwPeriod
AoiPwmPeriod is 255 or 63.
Example:
When button 0 is touched the desired AOI voltage is 0.30 Volts.
To calculate the AoiLevelBtnx is as follows (with AoiPwmPeriod=255):
Assuming a 3.3V VDD:
AoiLevelBtnx
≈ (Mean voltage / Maximum Voltage (VDD)) * AoiPmwPeriod
≈ (0.3/3.3) * 255 ≈ 23 decimal
Write 0x17 in the register AoiBtn0DutyCycle.
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5.7
DATASHEET
Buzzer Parameters
Buzzer Parameters
Address
Name
Bits
Description
0x37
BuzzerCfg
7:6
Defines the phase 1 duration.
0x00: ~ 5ms
0x01: ~ 10ms
0x02: ~ 15ms (default)
0x03: ~ 30ms
5:4
Defines the phase 2 duration.
0x00: ~ 5ms
0x01: ~ 10ms
0x02: ~ 15ms (default)
0x03: ~ 30ms
3
Defines the buzzer idle level (BuzzerLevelIdle).
0x0: min level (0V), (default)
0x1: max level (VDD)
2:0
Defines the buzzer pwm prescaler value.
Default: 0x04
0x38
BuzzerFreqPhase1
7:0
Defines the frequency for the first phase of the buzzer.
freq ≈ 4MHz /(2^prescaler * BuzzerFreqPhase1)
Default: 0x40 (4KHz)
0x39
BuzzerFreqPhase2
7:0
Defines the frequency for the second phase of the buzzer.
freq ≈ 4MHz /(2^prescaler * BuzzerFreqPhase2)
Default: 0x20 (8KHz)
0x3A
Reserved
7:0
Reserved (0x00)
Table 23 Buzzer Parameters
The buzzer parameters are described in section 3.7.
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5.8
DATASHEET
Mapping Parameters
Mapping Parameters
Address
Name
Bits
Description
0x3B
MapAutoLight0
7:4
GPIO[7]
Default: 0x0
3:0
GPIO[6]
Default: 0x7
7:4
GPIO[5]
Default: 0x6
3:0
GPIO[4]
Default: 0x5
7:4
GPIO[3]
Default: 0x4
3:0
GPIO[2]
Default: 0x3
7:4
GPIO[1]
Default: 0x2
3:0
GPIO[0]
Default: 0x1
0x3C
0x3D
0x3E
MapAutoLight1
MapAutoLight2
MapAutoLight3
Defines the mapping between GPOs (with
Autolight ON) and sensor events.
0x00: Btn0 or Proximity
0x01: Btn1
…
0x07: Btn7
0x08…0x0B: Reserved
0x0C: Group0 as defined by MapAutoLightGrp0
0x0D: Group1 as defined by MapAutoLightGrp1
0x0E: Reserved
0x0F: Reserved
Several GPOs can be mapped to the same sensor
event and will be controlled simultaneously.
0x3F
MapAutoLightGrp0Msb
7:0
Reserved (0x00)
0x40
MapAutoLightGrp0Lsb
7
Btn7
6
Btn6
5
Btn5
4
Btn4
3
Btn3
2
Btn2
All sensors events within the group can be
independently set.
1
Btn1
Default: 0x00
0
Btn0 or Proximity
Defines Group0 sensor events:
0: OFF
1: ON
If any of the enabled sensor events occurs the
Group0 event will occur as well.
0x41
MapAutoLightGrp1Msb
7:0
Reserved (0x00)
0x42
MapAutoLightGrp1Lsb
7
Btn7
6
Btn6
5
Btn5
4
Btn4
3
Btn3
2
Btn2
All sensors events within the group can be
independently set.
1
Btn1
Default: 0x00
0
Btn0 or Proximity
Defines Group1 sensor events:
0: OFF
1: ON
If any of the enabled sensor events occurs the
Group0 event will occur as well.
Table 24 Mapping Parameters
MapAutoLight0, MapAutoLight1, MapAutoLight2, MapAutoLight3
MapAutoLightGrp0Msb, MapAutoLightGrp0Lsb, MapAutoLightGrp1Msb, MapAutoLightGrp1Lsb
These registers define the mapping between the GPO pins (with Autolight ON) and the sensor information
which will control its ON/OFF state.
The mapping can be done to a specific sensor event but also on groups (in this case any sensor event in the
group will control the GPO).
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DATASHEET
Table 25 defines for each selectable sensor event, which action will trigger corresponding GPO to switch ON
or OFF.
MapAutoLight
BtnX
GPO ON
GPO OFF
Touch
Release
Table 25 Autolight Mapping, Sensor Information
Examples:
- If GPO[0] should change state accordingly to Btn4 then MapAutoLight3[3:0] should be set to 0x04.
- If GPO[0] should change state accordingly to Btn0 or Btn1 then Group0 can be used as following:
- MapAutoLight3[3:0] should be set to 0x0C (i.e. Group0).
- MapAutoLightGrp0 should be set to 0x0003 (i.e. Btn0 or Btn1)
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5.9
DATASHEET
GPIO Parameters
GPIO Parameters
Address
Name
Bits Description
0x43
GpioMode7_4
7:6 GPIO[7] Mode Defines the GPIO mode.
00: GPO
5:4 GPIO[6] Mode 01: GPP
3:2 GPIO[5] Mode 10: Reserved
11: SPO: AOI-A for GPIO[7],
1:0 GPIO[4] Mode
AOI-B for GPIO[6],
Buzzer for GPIO[5]),
7:6 GPIO[3] Mode
Reserved for GPIO[4..0]
5:4 GPIO[2] Mode
Default: 0xC000
3:2 GPIO[1] Mode
Default AOI-A
1:0 GPIO[0] Mode
Default GPO
0x44
GpioMode3_0
Default GPO
Default GPO
Default GPO
Default GPO
Default GPO
Default GPO
0x45
GpioIntensityOn0
0x46
GpioIntensityOn1
0x47
GpioIntensityOn2
0x48
GpioIntensityOn3
7:0 Defines the ON intensity index.
0x00: 0
7:0 0x01: 1
7:0 …
0xFF: 255 (default)
7:0
0x49
GpioIntensityOn4
7:0
0x4A
GpioIntensityOn5
7:0
0x4B
GpioIntensityOn6
7:0
0x4C
GpioIntensityOn7
7:0
0x4D
GpioIntensityOff0
0x4E
GpioIntensityOff1
0x4F
GpioIntensityOff2
0x50
GpioIntensityOff3
7:0 Defines the OFF intensity index.
0x00: 0
7:0 0x01: 1
7:0 …
0xFF: 255 (default)
7:0
0x51
GpioIntensityOff4
7:0
0x52
GpioIntensityOff5
7:0
0x53
GpioIntensityOff6
7:0
0x54
GpioIntensityOff7
7:0
0x56
GpioOutPwrUp
7:0 Defines the values of GPO and GPP pins after power up i.e. default values of
I2C parameters GpoCtrl and GppIntensity respectively.
Bits corresponding to GPO pins with Autolight ON should be left to 0.
Before being actually initialized GPIOs are set as inputs with pull up.
0: OFF(GPO) / IntensityOff (GPP)
1: ON (GPO) / IntensityOn (GPP)
Default: 0x00
0x57
GpioAutoLight
7:0 Enables Autolight in GPO mode.
0 : OFF
1 : ON
Default: 0xFF
0x58
GpioPolarity
Revision v3.2, January 2011
7:0 Defines the polarity of the GPO and GPP pins.
SPO pins require Normal Polarity.
0: Inverted
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DATASHEET
GPIO Parameters
Address
Name
Bits Description
1: Normal
Default: 0x80
0x59
GpioFunction
7:0 Defines the intensity index vs PWM pulse width function.
0: Logarithmic
1: Linear
Default: 0x80
0x5A
GpioIncFactor
7:0 Defines the fading increment factor.
0: intensity index incremented every increment time
1: intensity index incremented every 16 increment times
Default: 0x00
0x5B
GpioDecFactor
7:0 Defines the fading decrement factor.
0: intensity index decremented every decrement time
1: intensity index decremented every 16 decrement times
Default: 0x00
0x5C
GpioIncTime7_6
7:4 GPIO[7] Fading Increment Time
3:0 GPIO[6] Fading Increment Time
0x5D
GpioIncTime5_4
7:4 GPIO[5] Fading Increment Time
3:0 GPIO[4] Fading Increment Time
0x5E
GpioIncTime3_2
7:4 GPIO[3] Fading Increment Time
3:0 GPIO[2] Fading Increment Time
0x5F
GpioIncTime1_0
7:4 GPIO[1] Fading Increment Time
3:0 GPIO[0] Fading Increment Time
0x60
GpioDecTime7_6
7:4 GPIO[7] Fading Decrement Time
3:0 GPIO[6] Fading Decrement Time
0x61
GpioDecTime5_4
7:4 GPIO[5] Fading Decrement Time
3:0 GPIO[4] Fading Decrement Time
0x62
GpioDecTime3_2
7:4 GPIO[3] Fading Decrement Time
3:0 GPIO[2] Fading Decrement Time
0x63
GpioDecTime1_0
7:4 GPIO[1] Fading Decrement Time
3:0 GPIO[0] Fading Decrement Time
Defines the fading increment time.
0x0: OFF
0x1: 0.5ms
0x2: 1ms
…
0xF: 7.5ms
The total fading in time will be:
GpioIncTime*GpioIncFactor*
(GpioIntensityOn – GpioIntensityOff)
Default: 0x11111111
Defines the fading decrement time.
0x0: OFF
0x1: 0.5ms
0x2: 1ms
…
0x4: 2.0ms
…
0xF: 7.5ms
The total fading out time will be:
GpioDecTime*GpioDecFactor*
(GpioIntensityOn – GpioIntensityOff)
Default: 0x44444444
0x64
GpioOffDelay7_6
7:4 GPIO[7] OFF Delay
3:0 GPIO[6] OFF Delay
0x65
GpioOffDelay5_4
7:4 GPIO[5] OFF Delay
3:0 GPIO[4] OFF Delay
0x66
GpioOffDelay3_2
7:4 GPIO[3] OFF Delay
3:0 GPIO[2] OFF Delay
0x67
GpioOffDelay1_0
7:4 GPIO[1] OFF Delay
3:0 GPIO[0] OFF Delay
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Single Fading Mode
Defines the delay between release and start
of fading out.
0x0: instantaneous
0x1: 200 ms
0x2: 400 ms
0x3: 600ms
…
0xA: 2s
0xB: 4s
…
0xF: 12s
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DATASHEET
GPIO Parameters
Address
Name
Bits Description
Default: 0x00000000
0x68
GpioPullUpDown7_4
7:6 GPIO[7] Pullup/down
5:4 GPIO[6] Pullup/down
3:2 GPIO[5] Pullup/down
1:0 GPIO[4] Pullup/down
0x69
GpioPullUpDown3_0
7:6 GPIO[3] Pullup/down
Enables pullup/down resistors for GPIO pins.
00 : None
01 : Pullup
10 : Pulldown
11 : Reserved
Default: 0x0000
5:4 GPIO[2] Pullup/down
3:2 GPIO[1] Pullup/down
1:0 GPIO[0] Pullup/down
0x6A
Reserved
7:0 Reserved (0x00)
0x6B
Reserved
7:0 Reserved (0x00)
0x6C
Reserved
7:0 Reserved (0x00)
0x6D
GpioFadingMode7_4
7:6 Fading mode for GPIO[7]
5:4 Fading mode for GPIO[6]
3:2 Fading mode for GPIO[5]
1:0 Fading mode for GPIO[4]
0x6E
GpioFadingMode3_0
7:6 Fading mode for GPIO[3]
00: Single Fading Mode
01: Continuous Fading Mode
10: Reseved
11: Reserved
5:4 Fading mode for GPIO[2]
Default: 0x0000
3:2 Fading mode for GPIO[1]
The fading modes are expected to be
defined at power up by the QSM or NVM.
In case the fading modes need to be
changed after power up this can be done
when the GPOs are all OFF.
1:0 Fading mode for GPIO[0]
Revision v3.2, January 2011
Defines the Fading mode for GPO[7:0].
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Table 26 resumes the applicable SPM and I2C parameters for each GPIO mode.
SPM
I2C
1
GpioMode
GpioOutPwrUp
GpioAutolight
GpioPolarity
GpioIntensityOn
GpioIntensityOff
GpioFunction
GpioIncFactor
GpioDecFactor
GpioIncTime
GpioDecTime
GpioOffDelay
GpioPullUpDown
IrqSrc[4]
GpoCtrl
GppPinId
GppIntensity
GPP
X
1
X
X
1
X
1
X
X
GPO
X
2,3
X
X
X
X
X
X
X
X
X
X
X
X
SPO
5
X
4
X
1
X
At power up, GppIntensity of each GPP pin is initialized with GpioIntensityOn or GpioIntensityOff depending on GpioOutPwrUp
corresponding bits value.
2
Only if Autolight is OFF, else must be left to 0 (default value)
3
GpioOutPwrUp must be set to OFF in Continuous Fading Mode (with Autolight OFF)
4
Only if Autolight is OFF, else ignored
5
In SPO mode assure the following settings: GpioOutPwrUp=OFF, GpioAutoLight=ON, GpioPolarity=Normal, GpioFunction=Linear
Table 26 Applicable SPM/I2C Parameters vs. GPIO Mode
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6 I2C INTERFACE
The I2C implemented on the SX8661 is compliant with:
- standard (100kb/s), fast mode (400kb/s)
- slave mode
- 7 bit address (default 0x2B). The default address can be changed in the NVM at address 0x04.
The host can use the I2C to read and write data at any time. The effective changes will be applied at the next
processing phase (section 3.3).
Three types of registers are considered:
- status (read). These registers give information about the status of the capacitive buttons, GPIs, operation modes
etc…
- control (read/write). These registers control the soft reset, operating modes, GPIOs and offset compensation.
- SPM gateway (read/write). These registers are used for the communication between host and the SPM. The
SPM gateway communication is done typically at power up and is not supposed to be changed when the
application is running. The SPM needs to be re-stored each time the SX8661 is powered down.
The SPM can be stored permanently in the NVM memory of the SX8661. The SPM gateway communication over
the I2C at power up is then not required.
The I2C will be able to read and write from a start address and then perform read or writes sequentially, and the
address increments automatically.
The supported I2C access formats are described in the next sections.
6.1
I2C Write
The format of the I2C write is given in Figure 56.
After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The
SX8661 then acknowledges [A] that it is being addressed, and the master sends an 8 bit Data Byte consisting of
the SX8661 Register Address (RA). The slave acknowledges [A] and the master sends the appropriate 8 bit Data
Byte (WD0). Again the slave acknowledges [A]. In case the master needs to write more data, a succeeding 8 bit
Data Byte will follow (WD1), acknowledged by the slave [A]. This sequence will be repeated until the master
terminates the transfer with the Stop condition [P].
Figure 56 I2C write
The register address is incremented automatically when successive register data (WD1...WDn) is supplied by the
master.
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6.2
DATASHEET
I2C read
The format of the I2C read is given in Figure 57.
After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The
SX8661 then acknowledges [A] that it is being addressed, and the master responds with an 8 bit data consisting
of the Register Address (RA). The slave acknowledges [A] and the master sends the Repeated Start Condition
[Sr]. Once again, the slave address (SA) is sent, followed by an eighth bit (‘1’) indicating a Read.
The SX8661 responds with acknowledge [A] and the Read Data byte (RD0). If the master needs to read more
data it will acknowledge [A] and the SX8661 will send the next read byte (RD1). This sequence can be repeated
until the master terminates with a NACK [N] followed by a stop [P].
Figure 57 I2C read
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6.3
DATASHEET
I2C Registers Overview
Address
Name
R/W
Description
0x00
IrqSrc
read
Interrupt Source
0x01
Reserved
0x02
CapStat
read
Button Status
0x03
Reserved
0x04
Reserved
0x05
Reserved
0x06
Reserved
0x07
Reserved
0x08
SpmStat
read
SPM Status
0x09
CompOpMode
read/write
Compensation and
Operating Mode
0x0A
GpoCtrl
read/write
GPO Control
0x0B
GppPinId
read/write
GPP Pin Selection
0x0C
GppIntensity
read/write
GPP Intensity
0x0D
SpmCfg
read/write
SPM Configuration
0x0E
SpmBaseAddr
read/write
SPM Base Address
0x0F
Reserved
0xAC
SpmKeyMsb
read/write
SPM Key MSB
0xAD
SpmkeyLsb
read/write
SPM Key LSB
0xB1
SoftReset
read/write
Software Reset
Table 27 I2C Registers Overview
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6.4
DATASHEET
Status Registers
Address
0x00
Name
IrqSrc
Bits
Description
7
Reserved
6
NVM burn interrupt flag
5
SPM write interrupt flag
4
Reserved
3
Reserved
2
Buttons/Proximity interrupt flag
1
Compensation interrupt flag
0
Operating Mode interrupt flag
Interrupt source flags
0: Inactive (default)
1: Active
INTB goes low if any of
these bits is set.
More than one bit can be
set.
Reading IrqSrc clears it
together with INTB.
Table 28 Interrupt Source
The delay between the actual event and the flags indicating the interrupt source may be one scan period.
IrqSrc[6] is set once NVM burn procedure is completed.
IrqSrc[5] is set once SPM write is effective.
IrqSrc[2] is set if a Button/Proximity event occurred (touch or release if enabled). CapStatLsb show the detailed
status of the Buttons.
IrqSrc[1] is set once compensation procedure is completed either through automatic trigger or via host request.
IrqSrc[0] is set when actually entering Active or Doze mode via host request. CompOpmode shows the current
operation mode.
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Address Name
0x02
CapStat
Bits
Description
7
Status button 7
6
Status button 6
5
Status button 5
4
Status button 4
3
Status button 3
2
Status button 2
1
Status button 1
0
Status button 0
DATASHEET
Status of individual buttons
0: Released (default)
1: Touched
Table 29 I2C Cap status
Address
0x08
Name
Bits
Description
7:4
reserved
3
NvmValid
2:0
Indicates the number of times NVM has been burned:
0: None – QSM is used (default)
1: Once – NVM is used if NvmValid = 1, else QSM.
NvmCount
2: Twice – NVM is used if NvmValid = 1, else QSM.
3: Three times – NVM is used if NvmValid = 1, else QSM.
4: More than three times – QSM is used
Indicates if the current NVM is valid.
0: No – QSM is used
1: Yes – NVM is used
SpmStat
Table 30 I2C SPM status
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6.5
DATASHEET
Control Registers
Address Name
Bits
Description
7:3
Reserved*, write only ‘00000’
2
0x09
Compensation
Indicates/triggers compensation procedure
0: Compensation completed (default)
1: read -> compensation running ; write -> trigger
compensation
Operating Mode
Indicates/programs** operating mode
00: Active mode (default)
01: Doze mode
10: Sleep mode
11: Reserved
CompOpMode
1:0
* The reading of these reserved bits will return varying values.
** After the operating mode change (Active/Doze) the host should wait for INTB or 300ms before
performing any I2C read access.
Table 31 I2C compensation, operation modes
Address Name
0x0A
GpoCtrl
Bits
7:0
Description
GpoCtrl[7:0]
Triggers ON/OFF state of GPOs when Autolight is OFF
0: OFF (i.e. go to IntensityOff)
1: ON (i.e. go to IntensityOn)
Default is set by SPM parameter GpioOutPwrUp
Bits of non-GPO pins are ignored.
Table 32 I2C GPO Control
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Address
0x0B
Name
Bits
Description
7:3
Reserved, write only ‘00000’
GppPinId
2:0
GPP Pin Identifier
DATASHEET
Defines the GPP pin to which the GppIntensity is
assigned for the following read/write operations
0x0 = GPP0 (default)
0x1 = GPP1
...
0x7 = GPP7
GPPx refers to pin GPIOx configured as GPP
Table 33 I2C GPP Pin Identifier
Address
0x0C
Name
GppIntensity
Bits
7:0
Description
Defines the intensity index of the GPP pin selected in GppPinId
0x00: 0
0x01: 1
…
0xFF: 255
Reading returns the intensity index of the GPP pin selected in GppPinId.
Default value is IntensityOn or IntensityOff depending on GpioOutPwrUp.
Table 34 I2C GPP Intensity
Address
0xB1
Name
Bits
Description
SoftReset
7:0
Writing 0xDE followed by 0x00 will reset the chip.
Table 35 I2C Soft Reset
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6.6
DATASHEET
SPM Gateway Registers
The SX8661 I2C interface offers two registers for exchanging the SPM data with the host.
• SpmCfg
• SpmBaseAddr
Address
0x0D
Name
Bits
Description
7:6
00: Reserved
5:4
Defines the normal operation or SPM mode
00: I2C in normal operation mode (default)
01: I2C in SPM mode
10: Reserved
11: Reserved
3
Defines r/w direction of SPM
0: SPM write access (default)
1: SPM read access
2:0
000: Reserved
SpmCfg
Table 36 SPM access configuration
Address
Name
Bits
Description
0x0E
SpmBaseAddr
7:0
SPM Base Address (modulo 8).
The lowest address is 0x00 (default)
The highest address is 0x78.
Table 37 SPM Base Address
The exchange of data, read and write, between the host and the SPM is always done in bursts of eight bytes.
The base address of each burst of eight bytes is a modulo 8 number, starting at 0x00 and ending at 0x78.
The registers SpmKeyMsb and SpmKeyLsb are required for NVM programming as described in section 6.7.
Address
0xAC
Name
Bits
Description
SpmKeyMsb
7:0
SPM to NVM burn Key MSB
Unlock requires writing data: 0x62
Table 38 SPM Key MSB at I2C register address 0xAC
Address
0xAD
Name
Bits
Description
SpmKeyLsb
7:0
SPM to NVM burn Key LSB
Unlock requires writing data: 0x9D
Table 39 SPM Key LSB
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6.6.1
DATASHEET
SPM Write Sequence
The SPM must always be written in blocks of 8 bytes. The sequence is described below:
1. Set the I2C in SPM mode by writing “01” to SpmCfg[5:4] and SPM write access by writing ‘0’ to SpmCfg[3].
2. Write the SPM base address to SpmBaseAddr (The base address needs to be a value modulo 8).
3. Write the eight consecutive bytes to I2C address 0, 1, 2, …7
4. Terminate by writing “000” to SpmCfg[5:3].
Figure 58 SPM write sequence
The complete SPM can be written by repeating 16 times the cycles shown in Figure 58 using base addresses
0x00, 0x08, 0x10,…0x70, 0x78.
Once the SPM write sequence is actually applied, the INTB pin will be asserted. The host clears the interrupt by
reading any I2C register. At the same time the bit GenStatMsb[6], indicating the SPM write is done, will be
cleared.
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6.6.2
DATASHEET
SPM Read Sequence
The SPM must always be read in blocks of 8 bytes. The sequence is described below:
1. Set the I2C in SPM mode by writing “01” to SpmCfg[5:4] and SPM read access by writing ‘1’ to SpmCfg[3].
2. Write the SPM base address to SpmBaseAddr (The base address needs to be a value modulo 8).
3. Read the eight consecutive bytes from I2C address 0, 1, 2, …7
4. Terminate by writing “000” to SpmCfg[5:3].
Figure 59 SPM Read Sequence
The complete SPM can be read by repeating 16 times the cycles shown in Figure 59 using base addresses 0x00,
0x08, 0x10,…0x70, 0x78.
Once the SPM read sequence is actually applied, the INTB pin will be asserted. The host clears the interrupt by
reading any I2C register. At the same time the bit GenStatMsb[6], indicating the SPM write is done, will be
cleared.
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6.7
DATASHEET
NVM burn
The content of the SPM can be copied permanently (burned) into the NVM to be used as the new default
parameters. The burning of the NVM can be done up to three times and must be done only when the SPM is
completely written with the desired data.
The number of times the NVM has been burned can be monitored by reading NvmCycle from the I2C register
GenStatLsb[7:5].
Figure 60 Simplified Diagram NvmCycle
Figure 60 shows the simplified diagram of the NvmCycle counter. The SX8661 is delivered with empty NVM and
NvmCycle set to zero. The SPM points to the QSM.
Each NVM burn will increase the NvmCycle. At the fourth NVM burn the SX8661 switches definitely to the QSM.
The burning of the SPM into the NVM is done by executing a special sequence of four I2C commands.
1. Write the data 0x62 to the I2C register I2CKeyMsb.
2. Write the data 0x9D to the I2C register I2CKeyLsb.
3. Write the data 0xA5 to the I2C register I2CSpmBaseAddr.
4. Write the data 0x5A to the I2C register I2CSpmBaseAddr.
Terminate the I2C write by a STOP.
Terminate the I2C write by a STOP.
Terminate the I2C write by a STOP.
Terminate the I2C write by a STOP.
This is illustrated in Figure 61.
1)
S
SA
0
A
0xAC
A
0x62
A
P
2)
S
SA
0
A
0xAD
A
0x9D
A
P
3)
S
SA
0
A
0x0E
A
0xA5
A
P
4)
S
SA
0
A
0x0E
A
0x5A
A
P
S
SA
A
P
: Start condition
: Slave address
: Slave acknowledge
: Stop condition
From master to slave
From slave to master
Figure 61: NVM burn procedure
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7 APPLICATION INFORMATION
7.1
Triple proximity reporting
This section describes in further detail the quickstart application of chapter 3.1.
One AOI with seven LEDs are used. The intensity level of the LEDs show if proximity (medium intensity) or a
touch (maximum intensity) is detected. The LEDs are off in case no finger is present.
Figure 62 Typical Application (one AOI), triple proximity reporting
In case of proximity all LEDs (d0 to d6) are enabled to a medium intensity.
If a sensor is touched then only the corresponding LED will light up with full intensity. The other LEDs remain at
medium intensity.
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7.2
DATASHEET
Dual proximity reporting
Two AOIs and two LEDs are used. One LED is showing proximity and the second LED (or multiple LEDs) for
showing any touch.
Figure 63 Typical Application (two AOI), dual proximity reporting
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Figure 64 dual proximity LED and AOI reporting
Figure 64 shows the reporting on the LEDs and the AOI for the application with two AOIs.
On proximity all the LEDs (d1 to dx) are enabled to maximum light intensity.
A touch on any button is shown by the continuous fading in and fading out of the LED d0.
prox
key1
key2
key3
key4
key5
key6
key7
AOI-A
idle
0.6V
0.9V
1.2V
idle
idle
idle
idle
AOI-B
idle
idle
idle
idle
1.5V
1.8V
2.1V
2.4V
Table 40 example AOI-A, AOIB
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7.2.1
DATASHEET
SPM file (application two AOI, dual proximity reporting)
#Address[Hex]
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
0x0D
0x0E
0x0F
0x10
0x11
0x12
0x13
0x14
0x15
0x16
0x17
0x18
0x19
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
0x20
0x21
0x22
0x23
0x24
0x25
0x26
0x27
0x28
0x29
0x2A
0x2B
0x2C
0x2D
0x2E
0x2F
0x30
0x31
0x32
0x33
0x34
0x35
0x36
0x37
0x38
0x39
0x3A
0x3B
0x3C
0x3D
0x3E
0x3F
Value[Hex]
0xxx
0xxx
0x41
0xxx
0x2B
0x02
0x0D
0x00
0x00
0x05
0x00
0x55
0x57
0x73
0x33
0x33
0x33
0x00
0x00
0xA0
0xA0
0xA0
0xA0
0xA0
0xA0
0xA0
0xA0
0x00
0x00
0x00
0x0A
0x00
0x70
0x50
0x50
0x01
0x0A
0x00
0x80
0x00
0x00
0x00
0xFF
0x01
0xAA
0x55
0xFF
0x2E
0x45
0x5D
0x74
0x8B
0xA3
0xBA
0xFF
0xA4
0x40
0x20
0x00
0x00
0x00
0x00
0x0C
0x00
Revision v3.2, January 2011
#Address[Hex]
0x40
0x41
0x42
0x43
0x44
0x45
0x46
0x47
0x48
0x49
0x4A
0x4B
0x4C
0x4D
0x4E
0x4F
0x50
0x51
0x52
0x53
0x54
0x55
0x56
0x57
0x58
0x59
0x5A
0x5B
0x5C
0x5D
0x5E
0x5F
0x60
0x61
0x62
0x63
0x64
0x65
0x66
0x67
0x68
0x69
0x6A
0x6B
0x6C
0x6D
0x6E
0x6F
0x70
0x71
0x72
0x73
0x74
0x75
0x76
0x77
0x78
0x79
0x7A
0x7B
0x7C
0x7D
0x7E
0x7F
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Value[Hex]
0xFE
0x00
0x00
0xF0
0x00
0xFF
0xFF
0xFF
0xFF
0xFF
0xFF
0xFF
0xFF
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0xFF
0x00
0xC3
0xC0
0xC0
0x00
0x00
0x04
0x44
0x44
0x44
0x00
0x44
0x44
0x44
0x00
0xEE
0xEE
0xE0
0x00
0x00
0x00
0x00
0x00
0x00
0x01
0x50
0x74
0x10
0x45
0x03
0xFF
0xFF
0xFF
0xD5
0x55
0x55
0x7F
0x23
0x22
0x41
0xFF
0x3D
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7.3
DATASHEET
Example of Touch+Proximity Module
7.3.1 Overview
To demonstrate the proximity sensing feature of the SX8661/SX863x family, a module has been designed and is
illustrated in figure below.
Figure 65 Touch+Proximity Module Overview
The touch button controller is running in stand-alone (i.e. without host) and uses the Autolight mode to turn LEDs
ON/OFF accordingly to the touch buttons and proximity sensing status.
7.3.2
Operation
Module operation can be seen as 5 steps which are described in figure below
1. No finger
=> No proximity detected
=> All LEDs OFF
2. Finger approaches
=> Proximity detected
=> Blue LEDs turned ON
3. Button touch
=> Orange LED turned ON
(blue+orange = pink)
4. Button release
=> Orange LED turned
OFF
5. Finger removed
=> No proximity detected
=> Blue LEDs turned OFF
Figure 66 Touch+Proximity Module Operation
Notes:
- For better user experience, bicolor LEDs have been used here but one could decide to design a module with
normal unicolor LEDs. In this case, step 3 above would simply consist in a higher (blue) intensity for the LED of
the button touched.
- For obvious demonstration purposes the overlay used here is transparent but in typical applications (TV,
Monitor, Set-top box, etc) the overlay would be opaque enough so that when LEDs are OFF (i.e. no proximity
detected) the PCB is not visible to the user.
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7.3.3
DATASHEET
Performance
The proximity sensing distance of detection has been measured in these conditions:
- CapProxEnable = ON
- CapSensitivity = 7 (Max)
- CapThreshold = 300
- Board main supplied and placed vertically i.e. same orientation as hand/finger
- Finger pointing center button
The results obtained are provided in table below:
Palm
Finger (natural position)
Orthogonal finger (worst case)
Distance of Detection
~10cm
~6cm
~4cm
Table 41 Proximity Sensing Distance of Detection
7.3.4
Schematics
Figure 67 Touch+Proximity Module Schematics
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
7.3.5
DATASHEET
Layout
Figure 68 Touch+Proximity Module Layout - Top
Figure 69 Touch+Proximity Module Layout - Mid1
Figure 70 Touch+Proximity Module Layout - Mid2
Figure 71 Touch+Proximity Module Layout - Bottom
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
8 REFERENCES
[1] Capacitive Touch Sensing Layout guidelines on www.semtech.com
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
9 PACKAGING INFORMATION
9.1
Package Outline Drawing
SX8661 is assembled in a MLPQ-UT28 package as shown in Figure 72.
A
D
PIN 1
INDICATOR
(LASER MARK)
DIM
B
E
A2
A
aaa C
C
A1
A
A1
A2
b
D
D1
E
E1
e
L
N
aaa
bbb
DIMENSIONS
INCHES
MILLIMETERS
MIN NOM MAX MIN NOM MAX
.024
.001
(.006)
.006 .008 .010
.154 .157 .161
.100 .104 .108
.154 .157 .161
.100 .104 .108
.016 BSC
.012 .016 .020
28
.003
.004
.020
.000
0.60
0.02
(0.152)
0.15 0.20 0.25
3.90 4.00 4.10
2.55 2.65 2.75
3.90 4.00 4.10
2.55 2.65 2.75
0.40 BSC
0.30 0.40 0.50
28
0.08
0.10
0.50
0.00
SEATING
PLANE
LxN
D1
E/2
E1
2
1
N
e
bxN
D/2
bbb
C A B
NOTES:
1.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2.
COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS.
Figure 72 Package outline drawing
9.2
Land Pattern
The land pattern of MLPQ-UT28 package, 4 mm x 4 mm is shown in Figure 73.
Revision v3.2, January 2011
Figure 73 Land pattern
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SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
© Semtech 2011
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Contact Information
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Advanced Communications and Sensing Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111 Fax: (805) 498-3804
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