2. Schematic Checklist and PCB Layout Design
Figure 19: ESP32 UART Design
2.2.1.8 Touch Sensor
ESP32 offers up to 10 capacitive IOs that detect changes in capacitance on touch sensors due to finger contact or
proximity. The chip’s internal capacitance detection circuit features low noise and high sensitivity. It allows users to
use touch pads with smaller area to implement the touch detection function. Users can also use the touch panel
array to detect a larger area or more test points. Figure 20 depicts a typical touch sensor application.
Figure 20: A Typical Touch Sensor Application
In order to prevent capacitive coupling and other electrical interference to the sensitivity of the touch sensor system,
the following factors should be taken into account.
Electrode Pattern
The proper size and shape of an electrode improves system sensitivity. Round, oval, or shapes similar to a hu-
man fingertip is commonly applied. Large size or irregular shape might lead to incorrect responses from nearby
electrodes.
Note:
The examples illustrated in Figure 21 are not of actual scale. It is suggested that users use a human fingertip as reference.
Espressif Systems 15 ESP32 Hardware Design Guidelines V2.7
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