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87. Arduino Calculator

Hey everyone

Sorry I have not posted in a while. Today, I am back with an interesting project which is the Arduino Calculator. In this blog post, you will learn about the hardware components that are required for this project, the schematic and the explanation of the codes as well as a demonstration of this Arduino project.

Hardware components used in this project

  • Arduino Uno 
  • LCD display module with IIC interface - 16x2
  • Matrix Keypad - 4x4
  • Male-to-Female Jumper wires (x12)

Software required

  • Arduino IDE - latest version (preferred)

Schematic


Matrix Keypad


  • R1 - D9
  • R2 - D8
  • R3 - D7
  • R4 - D6
  • C1 - D5
  • C2 - D4
  • C3 - D3
  • C4 - D2


LCD Display module with IIC interface

  • GND (-) - Ground
  • VCC (+) - 5V
  • SDA - A4
  • SCL - A5

Coding

For this project, you will be needing the following libraries:
If you do not have the last two libraries installed, you can follow the hyperlink to read their documentation and access their repository. You can install the libraries from the respective Github repository or follow the instructions given in the respective Arduino reference page that can be accessed by following the hyperlink.

Create an LCD instance using the LiquidCrystal_I2C command and declare two variables that are of constant byte datatype. Name the variables as 'Rows' and 'Columns' and assign them to the value 4 as our matrix keypad has 4 columns and 4 rows. Create a few variables to store the value of the operands, operator and the answer.

Instantiate a keypad object that uses pins 9, 8, 7 and 6 as the row pins, and 5, 4, 3 and 2 as the column pins.
Create four user defined functions that will perform the calculations when 'A', 'B', 'C' or 'D' are pressed. Within void setup( ), initialize the LCD and set cursor to (4,0) and this is where you will print the welcome message but this is optional. Program the LCD display module to wait for 2 seconds and then clear its screen.

Within void loop( ),  create a character variable to store the value returned when any key is pressed. If any operator keys are pressed, print the value stored in the result variable and then print this operator. As the result variable has an initial value of 0, the first operand will be 0 in this case. If any number key is pressed, store the value returned in one of the number variables. If the '#' key is pressed, check the last value of the expression. If the last value is an operator, return an error message. If not, call the respective user defined function to perform the calculation and print the answer in the second row of the LCD. The operator variables should be assigned 0 and the operator variable must be empty after the calculation is done. If '*' key is pressed, clear the LCD. If any number key is pressed after a calculation is done and before clearing the screen (before '*' is pressed), you should program your microcontroller to automatically clear the screen.

Please watch the Youtube video in the next section of this post to get an understanding of how this works. 

Final Look


If you have any questions or suggestions regarding this project, please feel free to comment below. 





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