AN576
Si11 4
X
C
ONTROL
P
ANEL
A
PPLICATION
U
SER
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S
G
UIDE
1. Introduction
The Si114x control panel application enables the user to configure an Si1140DK or an IRslider2EK board quickly
and operate it in a way that is representative of the end application. The application enables ambient-light sensing
and proximity detection. The only Si114x features not supported are interrupt-driven accesses and autonomous
measurements. Instead, the application initiates forced measurement cycles asynchronously and performs
statistical computations (average and standard deviation) on the measurement results.
2. Getting Started
Upon startup, the user sees the following panel:
The Dashboard tab groups the main controls and results the user will be using for configuration and measurement.
The other tabs contain additional settings required for proximity, ambient light and auxiliary measurements.
Rev. 0.3 1/15
Copyright © 2015 by Silicon Laboratories
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3. Connecting the Evaluation Board
If a supported evaluation board is connected to a USB port prior to launching the application, its device code will
appear in real time in the device-selection drop-down menu on the upper-left corner, as in the figure below. Other
USB ports that appear in the menu, such as COM1, should be ignored. Select the board by its identifier
(TS0000C0B9 in this example) and click on the Connect button.
Once the evaluation board is connected to the application, the Si114x registers and parameters are read and
displayed on the application controls. If the board was just powered, the Si114x will be configured to its power-on
reset values. Refer to the Si114x data sheet for a complete list of the Si114x power-on reset values.
4. Measurement Channels
Once the above step is completed successfully, the evaluation board is ready to perform measurements. Six
measurement modes, called “channels,” are possible:
Three proximity-detection channels, each of which may use any combination of up to three infrared LEDs
A visible ambient-light channel
An infrared ambient-light channel
An internal “auxiliary” channel, typically used to monitor device temperature for precise offset control
Each channel can be enabled or disabled independently, depending on the system requirements. The main
proximity-measurement parameters, namely LED selection and current, can also be set in the Dashboard tab.
All controls, when set by the user, are instantly written to the Si114x and read back to the GUI for verification. Refer
to the Program Walk-Through section for a detailed description of control and result fields throughout the
application.
5. Making Measurements
Once the Si114x has been configured, measurements may be initiated by clicking on Measure Samples for a finite
number of measurements, or on Measure Continuous for continuous measurements. Refer to “7.1.4. Making
Accurate Lux Measurements” and "7.1.5. Making Proximity Measurements" on page 4 for details on performing
those respective measurements.
6. Exiting the Program
The application may be terminated by clicking on the Done button at the lower right-hand corner of the panel.
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7. Program Walk-Through
The following sections describe the program in detail.
7.1. Dashboard
Once the evaluation board is connected through the application, the Dashboard tab appears as shown below:
7.1.1. Interface Area
The Interface area displays the contents of the various Si114x registers that help identify the part and verify proper
connectivity. The I
2
C address shown is the global address (0).
7.1.2. Measurement Area
The Measurement area contains the basic configuration settings that define the Si114x’s mode of operation. The
proximity channels can also be reconfigured for ambient-light measurement, in which case all LED selections
should be disabled, and the PS_ADC_MODE must be set to “Raw ADC” in the next tab. For each LED, a different
current level can be programmed, but each LED is turned on at the same current level for all proximity channels
that make use of it.
7.1.3. Result Area
The
ADC_OFFSET
value is added to each measurement. It is needed to avoid very low readings to be
occasionally reported as negative when noise is present. An uncompressed value of 256 is normally adequate,
unless a larger system or ambient noise level warrants a higher value.
For each channel that is enabled, instant measurement results are displayed in the Sample field, while the average
and standard deviation are displayed in the Average and Sigma fields, respectively. Statistics are reset each time
Measure Samples, Measure Continuous or Capture Dark is clicked.
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7.1.4. Making Accurate Lux Measurements
The Si114x is capable of accurate lux measurements even under dark product overlays, such as tinted plastics or
dark ink silkscreened over toughened glass. Typically, those overlays appear dark but are fairly transparent to
infrared light, thus enabling unobstructed proximity detection. However, accurate ambient-light estimation requires
correction of the visible and infrared light measurements as seen through the overlay.
Accurate lux measurements require a “dark” value for each channel for proper coefficient weighting. In an actual
implementation, the dark values would be programmed empirically into the system software based on channel
gain, ambient light noise, supply voltage, etc. However, in a prototyping environment, the most expedient way to
obtain dark values is to cover the Si114x with dark material, such as black ESD foam, and click on the Capture
Dark button. If a lux measurement is attempted prior to capturing a dark value, a warning appears and default dark
values are used for the lux calculation.
Lux measurements typically use the visible and small infrared photodiodes, available in the ALS Visible and ALS IR
channels, respectively. While lux measurements are concerned only with visible light, the ALS IR channel is
required to subtract any residual infrared response in the ALS visible channel. Proper weighting of the visible
versus IR channel depends on the product overlay’s spectral characteristics. Whichever channel must be taken
into account for lux calculations must be enabled with the appropriate (nonzero) coefficient. Refer to “AN523:
Overlay Considerations for the Si114x Sensor” for coefficient selection based on product overlay.
7.1.5. Making Proximity Measurements
7.1.5.1. Typical Proximity Measurement Sequence
Proximity of a target is detected by the Si114x comparing the photodiode current with the LED turned on to the
photodiode current with the LED turned off, thus removing the offset caused by ambient light. Another kind of offset
is still present because of optical leakage, i.e. the amount of light caused by direct coupling between the LED and
the Si114x and by indirect coupling due to internal reflections. This offset is called the proximity baseline and must
be calibrated before accurate proximity detection can occur. In an actual system, the baseline is either set in the
factory or calculated dynamically, depending on system considerations. In a prototyping environment, the baseline
is captured after configuring the proximity settings.
After configuring the proximity channel or channels, the user must click on the “Capture baseline” button in the
Dashboard with no detectable object in front of the Si114x. Ideally, a very dark surface, such as photographic
focusing cloth, should be placed in front of the Si114x at several times the maximum intended detection distance. If
that is not practical, leaving the Si114x with “nothing” in front is often sufficient. Once captured, the proximity
baseline for each enabled channel is displayed in the corresponding data field in the result area of the Dashboard.
If any proximity setting is subsequently changed, the baseline is reset to zero.
After the baseline has been recorded, proximity measurements can be made by clicking either the “Measure
Samples” button or the “Measure Continuous” button, depending on the type of measurement desired. Proximity
counts, i.e. photodiode ADC counts with both ambient light and baseline offsets subtracted, are displayed for each
enabled channel in the corresponding data field in the result area of the Dashboard.
7.1.5.2. Proximity-Related Presets
A number of buttons are provided in the “Proximity-general” tab as shortcuts to configure the proximity channels for
various kinds of proximity measurements. The results of clicking each button are shown in the following table. After
a preset has been selected, the user is free to modify the Si114x settings to suit the exact requirements of the
application. The preset values may also be modified for each button by editing the settings.ini text file, which
resides in the same directory as the application's executable.
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Rev. 0.3
Button
PS1_ADCMUX,
PS2_ADCMUX,
PS3_ADCMUX
PS_ADC_GAIN
PS_LED1,
PS_LED2,
PS_LED3
Current
(High)
13, 269 mA
3, 22.4 mA
Normal
Range
Normal
Range
Normal
Range
High Range
1
Normal
Range
High
Range
Small IR
Photodiode
Large IR
Photodiode
1
4
Normal
Range
Large IR
Photodiode
1
16
Normal
Range
Large IR
Photodiode
16
Normal
Range
Normal
Range
Normal
Range
1
High Range
1
Normal
Range
Small IR
Photodiode
1
Normal
Range
PS_LED1,
PS_LED2,
PS_LED3
Current
(Low)
PS_RANGE
ALS_VIS_
ADC_GAIN
VIS_
RANGE
ALS_IR_A
DCMUX
ALS_IR_ADC
_GAIN
IR_RANGE
PS_ADC_MODE
Reset
defaults
4
13, 269 mA
3, 22.4 mA
Large IR
photodiode
1
Normal Proximity
Low light
Large IR
photodiode
1
15, 359 mA
4, 45 mA
Normal Proximity
High
sensitivity
1
15, 359 mA
7, 112 mA
Large IR
photodiode
Normal Proximity
High
signal
1
15, 359 mA
10, 180 mA
High Range
1
Large IR
photodiode
Normal Proximity
Sunlight
Small IR
photodiode
Normal Proximity
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