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CapTIvate™ Touch Getting Started Manual
23
Copyright © 2021, Texas Instruments Incorporated
direct relationship between the two and LTA is shown in formulas 5-4 and 5-5. In addition, it can be seen from
formula 5-2 that Delta has a parallel relationship with
∆𝐶
𝑡𝑜𝑢𝑐ℎ
. This is also the reason why Prox/ Touch Threshold
and Prox/ Touch Threshold Percentage are different, because the latter directly characterizes the change in touch
capacitance.
|𝐷𝑒𝑙𝑡𝑎| = Prox Threshold
(5-4)
|𝐷𝑒𝑙𝑡𝑎| = LTA ∗
Touch Threshold
128
(5-5)
Other Thresholds will determine the setting events of the Touch flag and Proximity flag of the entire Sensor. For
example, the MCU is powered on when a human hand touches it. At this time, the touch signal of the human hand
will be counted as the base capacitance of the environment. At this time, removing the finger will generate a
negative signal. When the negative signal reaches the Negative Threshold, system calibration will be triggered.
Debounce in/out threshold will introduce a signal anti-jitter mechanism to combat noise, which will delay the
response of the button to a certain extent. The Sensor Timeout Threshold is used to prevent environmental
changes from triggering the Prox Threshold situation. After the threshold is triggered, the system will recalibrate
the environmental base capacitance.
5.1.4
Object structure in CapTIvate™
Figure 5-6 T
he object structure in CapTIvate™
There are four types of objects in CapTIvate™, Top Level, Sensor, Cycle, and Element. Figure 5
-6 shows the parent-
child relationship between different structures, and also gives the object name, structure name, and actual naming
Top Level is used to describe the working mode of MCU. It belongs to the abstract concept of MCU. It corresponds
to the MCU widget in the GUI, and the parameters configured by the MCU widget hang under the Top-Level
structure. This part of the content is in 5.1.1 of this chapter. Discussed in the subsection, Sensor, Cycle, and
Element correspond to the sensor widgets in the GUI. The parameters configured by the sensor widgets are placed
under these three structures. This part of the content is also discussed in section 5.1.2 of this chapter.
Sensor corresponds to the five sensor forms of button panel, proximity sensor, scroll wheel, slider, touch panel,
and proximity sensor, which belong to the abstract concept of physical sensors, so there will be multiple Sensor
objects in a system.
Since one capacitance detection module of CapTIvate™ MCU corresponds to 4 CAP IOs, it is necessary to
select the
scanned IO ports sequentially by chip selection, so Cycle corresponds to each round of scanning.
Element is an abstract concept of physical buttons. All Sensor modes, button panels, proximity sensors, scroll
wheels, sliders, and touch panels are essentially based on the signals measured by each button, and then
processed on the software to obtain the corresponding zero-dimensional, one-dimensional, and two-dimensional
