Adding capacitive sensing to a consumer or industrial product can be a daunting challenge that requires developers to maintain sensor robustness and responsiveness while minimizing current consumption and addressing other system-level design priorities. Navigating this embedded development process without the help of tools and support can lead to lengthy trial-and-error design iterations, both in software and hardware, resulting in slipped release schedules and suboptimal solutions.
While fixed-function capacitive-sensing solutions can ease some of these design burdens, those devices are rarely pure drop-in solutions, as many still rely on developer-side configuration and calibration. In addition, fixed-function solutions prevent developers from giving the sensor additional responsibilities in a system, which can help reduce system current consumption, board size, and bill-of-materials (BOM) cost.
Capacitive-sensing solutions based on general-purpose 8-bit microcontrollers (MCUs) can help designers through each step of the development process, enabling them to generate projects using capacitive-sensing firmware libraries, add and debug features with an intuitive and powerful integrated development environment (IDE), and view real-time capacitive-sensing performance in-system using capacitive-sensing visualization tools.
Capacitive-Sensing Design Basics
Capacitive-sensing technologies measure the capacitance of an electrode connected to the sensor’s input. The electrode being measured is often a printed-circuit-board (PCB)-designed round pattern of solid copper about 10 mm in diameter that’s isolated from the board’s ground. A thin overlay, usually made of a type of plastic or glass, is sometimes adhered to the PCB, and the resulting system can function as a touch interface that doesn’t require mechanical buttons.