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The second mode is button algorithm mode. Here further processing with parameters defined by the user (see
) is done on the data and a button thresholding as defined
by the user is applied. The processed data are available in separate registers to be read by I
2
C and any button
press detection is indicated on the OUTx pins (see
) This mode is used to implement
button press functionality and can also be used to implement the measurement of force applied for button press
along with detection to implement multilevel button press.
For register settings that are applicable to button mode versus raw access data mode are clearly identified in the
descriptions of the registers (see
L to
Digital
Converter
LC Driver
&
Sampler
Baseline
Tracking
Button
Press
Detection
OUTx, INTB Pins
DATAx Regs
I2C Add: 0x02-0x09
INTB Pin
RAW_DATAx Regs
I2C Add: 0x59-0x64
BTN_ALG_EN=1
BTN_ALG_EN=0
Figure 7-2. Multimode Operation in LDC3114
7.3.2 Multichannel and Single-Channel Operation
The LDC3114 provides four independent sensing channels. In the following sections, some parameters, such as
DATA
n
and SENSOR
n
_CONFIG, contain a channel index
n
.
Any of the four channels available in the LDC3114 can be independently enabled by setting the EN
n
and LPEN
n
(
n
= 0, 1, 2, or 3) bit fields in
Register EN (Address 0x0C)
. The low-power-enable bit LPEN
n
only takes effect
if the corresponding EN
n
bit is also set. If only one channel is set active, the LDC3114 periodically samples the
single active channel at the configured scan rate. When several channels are set active, the LDC3114 operates
in multichannel mode, and the device sequentially samples the active channels at the configured scan rate. Each
channel of the LDC3114 can be independently enabled in Low Power Mode and Normal Power Mode.
7.3.3 Raw Data Output
Raw data mode is enabled by setting
BTN_ALG_EN=0x0
field in
Register INTPOL Address 0x11
.
shows that this operation will extract data directly from the output of the inductance-to-digital converter.
The data is read from the I
2
C interface of the LDC3114. The
DATA_RDY
field in
Register OUT (Address 0x01)
indicates when new data is available for reading. In the raw data mode, the INTB pin also assserted when new
data is available and can be used by the MCU as an interrupt. The raw data can be extracted by reading, the
output RAW_DATA
n
_
x
registers (
n
= 0, 1, 2, or 3, for each channel,
x
= 1, 2, or 3 splitting 24-bit data over 3 8-bit
register fields).
shows the relationship between 24-bit data and the sensor frequency.
REF _ CLK
SENSOR
30 W
f
f
raw _ data
u
u
(1)
where:
• f
sensor
is the instantaneous frequency of the inductive sensor
• f
REF_CLK
is the internal reference clock frequency as specified in
• raw_data is the decimal representation of 24-bit binary data read from the RAW_DATAn_x for a particular
channel
Programming Button or Raw Data Sampling Window
LCDIV
W
128
1
SENCY
2
u
u
n
(2)
SNOSDD0 – DECEMBER 2021
10
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