These Keypad Matrix use I2C to communicate, 2 pins are required to interface. The Keypad Matrix has an interrupt pin to provide fast detection of changes. This example shows the working of polling.

A keypad is one of the most commonly used input devices in microprocessor applications. In a standard keypad wired as an X-Y switch matrix, normally-open switches connect a row to a column when ...

[Andrea] just sent us this great student hack he made for his room. He’s constructed an Arduino keypad door lock — without using any proper fastening hardware! The entire build is made out of scrap ...