Cypress CapSense CY8C20x36 Uživatelská příručka stáhnout pdf (Strana 10)

10 Document No. 001-64846 Rev. *I Getting Started with CapSense

2. CapSense Technology

Cypress‘s CapSense controllers use changes in capacitance to detect the presence of a finger on or near a touch

surface, as shown in Figure 2-1. This touch button example illustrates a capacitive sensor replacing a mechanical

button. The sensing function is achieved using a combination of hardware and firmware. The following section

provides an overview of capacitive sensing technology and CapSense solutions.

Figure 2-1. Illustration of a Capacitance Sensor Application

2.1 Capacitive Sensing Methods

Capacitance can be measured between two points using either self-capacitance or mutual-capacitance.

Figure 2-2. Self-Capacitance and Mutual-Capacitance Methods

_ C

Self Capacitance

Tx Rx

Mutual Capacitance

2.1.1 Self-Capacitance

Self-capacitance uses a single pin and measures the capacitance between that pin and ground. A self-capacitance

sensing system operates by driving current on a pin connected to a sensor and measuring the voltage. When a finger

is placed on the sensor, it increases the measured capacitance. Self-capacitance sensing is best suited for single-

touch sensors, such as buttons and sliders.

Cypress‘s CapSense solutions use self-capacitance sensing. This approach makes efficient use of pins for single

touch sensors and sliders.

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Cypress CapSense CY8C20x36 Uživatelská příručka Strana 10