4×4 Matrix Keypad Membrane Switch for Arduino, ARM and other MCU

This Matrix Keypad 4 X 4 has 16 buttons, arranged in a telephone-line 3x4 grid with a column of 4 characters (A, B, C, and D). The keys are connected into a matrix, hence only 8 microcontroller pins (4-columns and 4-rows) are required to scan the pad. It's made of a thin, flexible membrane material with an adhesive backing (just remove the paper) so you can attach it to nearly anything. The keys are connected into a matrix, so you only need 8 microcontroller pins (4-columns and 4-rows) to scan through the pad.