This Application Note describes programming techniques implemented on the AT91 ARM-based microcontroller for scanning a 4x4 Keyboard matrix usually found in both consumer and industrial applications for numeric data entry.

This section focuses on a typical 4x4 matrix keypad, but you can use the same technique with a matrix keypad of any dimensions. A matrix keypad can be connected to the PSoC 1 without using any external components as shown

4x4 Matrix Keypad Interface with Atmel AVR.