Making Two digit calculator with Arduino uno , 16x2 lcd and 4x4 numeric keypad

This tutorial is about making arduino calculator. We will build two digit arduino calculator using arduino uno, 4×4 numeric keypad and 16×2 lcd. This particular arduino calculator can perform six functions addition, subtraction, multiplication, division, power and reminder. Code is easy to understand but its lengthy. If you are already familiar with the arduino coding syntax, you can easily understand the code below. If you are not than take some tutorials to become familiar with arduino language syntax.

Arduino calculator project requirements

Arduino uno (Microcontroller)
4×4 Keypad (Taking input from Users)
16×2 Lcd (Displays Result)
Potentiometer (Setting Lcd Contrast)

Arduino uno is used as microcontroller in the project. Arduino takes the input from user and after analyzing the instructions produces output. The output is than displayed on 16×2 lcd. 4×4 numeric keypad is used as input. User presses the buttons on keypad to give input to arduino calculator. Arduino calculator takes two digits and an operator as input. Arduino calculator then identifies the operator, computes results according to the operator and then displays the result on 16×2 lcd screen.

Lcd 16×2 is interfaced in 4-bit mode with arduino uno. Arduino pins D13, D12, D11, D10, D9 and D8 are occupied by 16×2 lcd. 4×4 Keypad rows are connected to pins D4, D5, D6 & D7 of arduino uno. Coulombs of keypad are connected to pins D0, D1, D2 & D3 of arduino uno.

The lay out arduino calculator keypad is given below. All the six mathematics functions which our calculator can perform are mapped on the keypad.
Note: You may see buttons text printed on your 4×4 keypad different then the keypad shown below. Actually buttons text did not mean any thing. What we define or map on keypad keys at controller side will be performed by the keypad. So in our case i lay out the mapping on keypad shown below. Instead of power and reminder operator you will find “On” and “=” printed on keypad in most of the cases.

Arduino calculator keypad

Its not possible to explain how to interface 16×2 lcd with arduino uno? In what modes lcd 16×2 can be interfaced with arduino? and How to operate it. Its also not possible to explain the interface of 4×4 numeric keypad with arduino uno. If you seeking the results of above questions i recommend you to take the tutorials listed below. These tutorials are about interfacing of 16×2 lcd and 4×4 keypad with arduino.

How to interface 16×2 lcd in 4-bit mode with arduino

The tutorials above are very important. If you take them its become easier for you to understand the arduino calculator code below. If you already know how to interface character lcd (16×2) and 4×4 keypad with arduino, you can skip the above tutorials. Circuit Diagram of the project is given below.

Arduino calculator (arduino uno, 16x2 lcd, 4x4 numeric keypad)circuit diagram

Arduino calculator (arduino uno, 16×2 lcd, 4×4 numeric keypad)circuit diagram

Calculator with Arduino uno, 16x2 lcd and 4x4 keypad--Circuit Diagram

Calculator with Arduino uno, 16×2 lcd and 4×4 keypad–Circuit Diagram

Arduino calculator code

First off all in the code i exported Liquid Crystal library. Liquid Crystal library contains predefined functions which could be used in arduino code to easily interface and operate 16×2 lcd with arduino uno. I am interfacing 16×2 lcd in 4-bit mode with arduino uno. Comming to wards the key functions which are part of the arduino calculator code. Each function name with the functions they perform are listed below.

int getKey () is taking inputs, digits from keypad.
char getOper() is taking input , Operator from keypad.
void result (float result) Displaying result on lcd.

Next two statements define rows and coulombs of keypad. key1 is an integer variable, it stores first digit which is inputted by user using 4×4 keypad. key2 is an another integer variable, it stores second digit inputted by the user. oper is character variable it stores the operator inputted by user through keypad.

In setup() function, lcd.begin(16,2) statement initializes the lcd. This tells the 16×2 lcd controller to begin operation. Command passes some constraints to controller and tells it to operate in this mode with 16 coulombs and 2 rows After wards rows of keypad are initialized as output and coulombs are initialized as input.

The first string that appears on the screen when you download the code in arduino uno board and run it is “CALCULATOR!!!!“. It will be displayed on the first row of 16×2 character lcd. It will remain on the screen for 4 seconds delay(4000) statement means stop execution of instructions for 4 seconds. After 4 seconds “CALCULATOR!!!” string vanishes and a new text string will prompt on lcd. New text will be “Enter 1 no = “. Now you have to enter the first digit using keypad. After you enter the first number second text will appear on 16×2 lcd asking for second digit “Enter 2 no = “. At this point you have to enter the second digit. Than a third string appears on lcd asking to input operator “Operator = “. You now must select the operator from keyboard. As soon as you enter the operator result will be displayed on lcd with out any further delay. Result of a particular inputs remain on lcd for 5 seconds. After 5 seconds lcd clears all the text displayed on it and starts from beginning. Taking digits, operator etc and producing results.

More calculator projects using other different types microcontrollers are listed below. Each microcontroller calculator project contains free source code and circuit diagram of the project.

Calculator with Pic Microcontroller

Calculator with 8051 Microcontroller

Watch the Project Video Here…..

Download the Project Files that contain code and .ino file of the project. If you have any questions regarding code or circuit diagram, Please write them in the comments section below. Give us your feed back on the project.

Calculator using Arduino Uno Files