SLAU857 User guide

SLAU857A May 2021 – July 2021 MSP430FR2476 , MSP430FR2512 , MSP430FR2522 , MSP430FR2532 , MSP430FR2533 , MSP430FR2632 , MSP430FR2633 , MSP430FR2672 , MSP430FR2673 , MSP430FR2675 , MSP430FR2676

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3.1.2 Slider or Wheel

Both the slider and the roller are one-dimensional linear sensors, and their implementation principles and structures are similar. Because the base capacitance of mutual-capacitive detection is low and the signal fluctuates more than in self-capacitive detection, mutual-capacitive detection is less often used in sliders or wheels. Therefore, only the self-inductance slider or wheel is discussed, as shown in Figure 3-4.

The basic structure of the slider or wheel is the buttons. By interlacing the buttons, when the human hand moves, because the contact area of the two adjacent buttons is different, the movement of the signal can be detected. In addition, the two copper coatings at the beginning and the end of the slider are connected together by wires and belong to the same button.

For self-capacitive sliders and scroll wheels, at least 3 MCU CAP I/O pins are required. The resolution range of the sliders or scroll wheels supported by the software is 3 to 65535. The actual number of CAP I/O pins occupied and the selected resolution must be adjusted according to the requirements of the application.

Figure 3-4 Self-Capacitive Slider or Wheel PCB