Introduction to Capacitive Sensing

Capacitive sensing is becoming more prevalent and in demand for consumer applications. This application note introduces one solution for capacitive sensing using several Microchip parts. The targeted parts of this application note are the PIC16F616 family, the PIC16F690 family and the PIC16F887 family, representing low-to-high pin count, 8-bit microcontrollers.

There are several techniques for capacitive sensing currently being used in the industry. Many are based on measuring a frequency or duty cycle, which is changed by the introduction of additional capacitance from a person's finger to the ground. Some other methods use charge balancing or rise and fall time measurements. The solution described here measures frequency using a free-running RC oscillator.