The following covers the pinout for the various key pad products.

General Nomenclature

Each keypad is a combination of row and column circuits. The buttons themselves are simple switch like closures in these circuits. Here's an example of a basic 4x4 keypad arrangement.

There is 1 pin for each column and 1 pin for each row. So for the 4x4 keypad, there are 4 + 4 = 8 total pins. For the 3x4 keypad, there are 3 + 4 = 7 pins. Etc. Each of these needs to be connected to a separate digital pin on the microcontroller.

In the diagram above, the pins 1-4 correspond to the columns while pins 5-8 correspond to rows. Determining if a particular button is pressed is done by programmatically changing the digital pins between input and output and reading pin state. Doing this across all possible pin combinations is referred to as a scan. All of that work is typically taken care of for you in a library.

4x4 Matrix Keypad (PID 3844)


3x4 Matrix Keypad (PID 3845)


3x4 Phone-style Matrix Keypad (PID 1824)


Membrane 3x4 Matrix Keypad (PID 419)


Membrane 1x4 Matrix Keypad (PID 1332)


This guide was first published on Nov 06, 2018. It was last updated on Feb 19, 2024.

This page (Pinouts) was last updated on Mar 27, 2020.

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