Table 17. Touch-Sensing-Related Configuration Elements - ST STM32L4R9I-EVAL User Manual

UM2248
An active shield is designed in layer 2 of the main PCB, under the button footprint. It allows
reducing disturbances from other circuits to prevent false touch detections.
The active shield is connected to the PB6 port of STM32L4R9AII6 through the resistor R22.
The related charge capacitor is connected to PB7.
Table 17
them serve to enable or disable its operation. However, most of them serve to optimize the
touch sensing performance, by isolating copper tracks to avoid disturbances due to their
antenna effect.
.
Element
R44
SB21
R46
SB19
SB20
R26
SB14
SB15
shows the configuration elements related to the touch sensing function. Some of

Table 17. Touch-sensing-related configuration elements

Setting
PC6 port is routed to the CN6 connector of the daughterboard.
In
This setting is not good for the robustness of touch sensing.
Default setting.
Out
PC6 port is cut from CN6.
Default setting.
Open
PC6 is not routed to motor control.
PC6 is routed to motor control.
Closed
This setting is not good for the robustness of touch sensing.
PC7 port is routed to the CN6 connector of the daughterboard.
In
This setting is not good for the robustness of touch sensing.
Default setting.
Out
PC7 port is cut from CN6.
Default setting.
Open
PC7 is not routed to motor control.
PC7 is routed to motor control.
Closed
This setting is not good for the robustness of touch sensing.
PC7 is not routed to the sampling capacitor. Touch sensing cannot
Open
operate.
Default setting.
Closed
PC7 is routed to the sampling capacitor. Touch sensing available.
PB6 port is routed to the CN5 connector of the daughterboard.
In
This setting is not good for the robustness of touch sensing.
Default setting.
Out
PB6 port is cut from CN5.
Default setting.
Open
PB6 is not routed to motor control.
PB6 is routed to motor control.
Closed
This setting is not good for the robustness of touch sensing.
PB6 is not routed to the active shield under the touch sensing button.
Open
This setting is not good for the robustness of touch sensing.
Configuration
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Hardware layout and configuration
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