ABSTRACT
This chapter discusses the two most commonly used devices for microcontrollers: the switch and the keypad. Common switch types are rocker, toggle, pushbutton, dual inline package, rotary, tactile, slide, keylock, snap-action, thumbwheel, and several others. Switches are classified according to the various contact arrangements. In the normally-open switch, the contacts are separated until some force causes them to close. In the normally-closed switch, the contacts are held together until some force separates them. Some switches can be selected to operate as either normally open or normally closed. In the world of microcontroller-based circuits, a keypad is a set of pushbutton switches sometimes labeled with digits, mathematical symbols, or letters of the alphabet. In this sense, a calculator keypad contains the decimal digits, the decimal point, as well as keys for the mathematical features of the calculator. Keypads are usually implemented as pushbutton switches located in a row and column matrix. Keypads, like the switches they incorporate, require debouncing.
