One single analog pin keypad control using Arduino

Overview

In this tutorial, we will learn how to interfacing 4*4 keypad with Arduino by a single analog pin. The use of a lot of pins can be reduced by following this procedure. It helps to use rest of pins for another purpose. For this tutorial, we will use a single analog pin to interfacing keypad with Arduino. 

You can watch the following video below:-

Components Required

The required components list for this tutorial given below:-

• Arduino Uno.
• 4*4 keypad.
• Three 4.7k resistors.
• Four 1k resistors.
• One 220ohm resistor.
• LCD display.
• 10k potentiometer.
• Some jumper wire.

  

  Fig:1.1

Keypad Pinout

The following below figure shows 4*4 keypad pinout. 

Fig 2.1: 4*4 Keypad Pinout

Circuit Schematic

The given below schematic is single wire keypad with Arduino:- 

Fig 3.1: One wire keypad with Arduino

Circuit Description

One single analog pin keypad control based on basic voltage divider role. The voltage increase gradually from left to right (Fig: 4.1) in the row and up to down (Fig: 4.1) in the column. The voltage is minimum at the first-row first column and the maximum voltage is at point row 4 and column 4. Three 4.7k ohm resistors will gradually connect between row 1 to  2, 2 to 3, 3 to 4. Similarly, three 1k ohm resistors will connect between column 1 to 2, 2 to 3, and 3 to 4 respectively. The remaining one 1k ohm resistor will go to ground from column 1. Next +5V will connect with row 1 and analog input A0 pin from Arduino will connect with column 1. 

Fig: 4.1

The first pin of LCD from left is Gnd pin which will connect with Arduino ground pin. Next LCD pin R/W 5  and cathode pin16 will also go to ground. The second pin of LCD is Vcc which connect with Arduino +5V. The anode pin 16 of LCD operated on 5V, a 220-ohm resistor should be connected in series to this pin. Next comes to the VEE (Pin 3) which is LCD contrast adjustment pin that will be connected a 10k potentiometer to +5V and ground, with its wiper (output) pin. The LCD rs and enable pin 4 and 6 will connect with Arduino digital pin 2 and 3 respectively. Next LCD pin D3 to D7 gradually connect with Arduino digital pin 4 to 7.   

Fig 4.2: One wire keypad with LCD using Arduino

Source Code

One wire keypad with Arduino source code is given below:-

One wire keypad with LCD using Arduino source code is given below:-


You can download the library here: https://github.com/AndrewMascolo/OnewireKeypad