Touch Sensor; Electrode Pattern; Pcb Layout - Espressif Systems ESP32 Hardware Design Manuallines

Chapter 4. PCB Layout Design
• It is better to surround the SDIO_CLK trace with ground copper. The path from SDIO GPIOs to the master
SDIO interface should be as short as possible and no more than 2500 mil or even 2000 mil.
• Do not place SDIO traces across planes.

4.10 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 to use
touch pads with smaller area to implement the touch detection function. You can also use the touch panel array to
detect a larger area or more test points.
Figure ESP32 Typical Touch Sensor Application
To prevent capacitive coupling and other electrical interference to the sensitivity of the touch sensor system, the
following factors should be taken into account.

4.10.1 Electrode Pattern

The proper size and shape of an electrode improves system sensitivity. Round, oval, or shapes similar to a human fin-
gertip are commonly applied. Large size or irregular shape might lead to incorrect responses from nearby electrodes.
Figure ESP32 Electrode Pattern Requirements
that the examples illustrated in the figure are not of actual scale. It is suggested to use a human fingertip as reference.

4.10.2 PCB Layout

Figure ESP32 Sensor Track Routing Requirements
• The trace should be as short as possible and no longer than 300 mm.
• The trace width (W) can not be larger than 0.18 mm (7 mil).
• The alignment angle (R) should not be less than 90°.
• The trace-to-ground gap (S) should be in the range of 0.5 mm to 1 mm.
• The electrode diameter (D) should be in the range of 8 mm to 15 mm.
• Hatched ground should be added around the electrodes and traces.
• The traces should be isolated well and routed away from that of the antenna.
Note: For more details on the hardware design of the touch sensor, please refer to
Espressif Systems
depicts a typical touch sensor application.
Fig. 13: ESP32 Typical Touch Sensor Application
shows the proper and improper size or shape of electrode. Please note
illustrates the general guidelines to routing traces. Specifically,
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Touch Sensor Application
Release master
Note.