# Keypad Scanning

The 3x4 and 4x4 matrix keyboards are commonly used for user input. Usually,
the row and column wires are connected to GPIO pins on a microcontroller. A
simple approach requires 7 wires for a 3x4 keypad.

[This article](keypad_to_microcontroller.md) introduces a new technique wish reduces the number of GPIO pins
down to 6, 5 and even 4, using software scanning techniques and diodes.

Even though this reduces GPIO pin requirements in a manner similar to 
[charliplexing](https://en.wikipedia.org/wiki/Charlieplexing), this is a
*different* design.