Circuit Lake

by Sandeep M Satav, Indian Institute of Technology, Bombay, India

Designers of microcontroller-based products that require a keypad for user data entry can select from dedicating an input line for each key, continuously polling the keypad’s x and y lines, or generating an interrupt whenever a user presses a key. Although conceptually simple, dedicating lines to a keypad can tie up most of the microcontroller’s I/O resources. Continuously polled keypads can burden the microprocessor’s resources and consume excessive amounts of battery power.
The third method, an interrupt-driven keypad, offers several benefits. First, using interrupts frees the microcontroller to perform other tasks or to switch into an idling or power-down mode while awaiting the next key closure. Second, using interrupts helps reduce electromagnetic interference produced by continuously scanning the keypad’s lines.

Link: EDN magazine