DIY-Calculator

The REAL Chinese Calculator

An advanced floating-point calculator project for Arduino using a 4x5 matrix keypad and an I2C LCD display. This calculator supports standard arithmetic, chaining operations, modulo, and a unique Power/Root mode selector.

Features

• Basic Arithmetic: Addition (+), Subtraction (-), Multiplication (*), Division (/).
• Scientific Operations:
  • Modulo (B): Calculates the remainder of a division.
  • Power & Root (A): A submenu allows you to choose between calculating $x^y$ (Power) or $\sqrt[y]{x}$ (Root).
• Smart Formatting: Automatically switches between integer display, fixed decimals, and scientific notation based on result size.
• Error Handling: Protects against Division by 0, Modulo by 0, and imaginary numbers (even roots of negative numbers).
• Chain Calculations: Immediately use the result of the previous calculation as the start of the next one.

Hardware Requirements

Microcontroller: Arduino Uno, Nano, or compatible.

• Display: 16x2 LCD with I2C Backpack (Address: 0x27).
• Input: 4x5 Matrix Keypad (Membrane or Mechanical).
• Connections: Jumper wires.

Wiring & Pinout

Based on the code configuration, connect your components as follows:

Keypad Connection

Keypad Pin	Arduino Pin	Function
Row 1	D2	Row
Row 2	D3	Row
Row 3	D4	Row
Row 4	D5	Row
Col 1	D6	Column
Col 2	D7	Column
Col 3	D8	Column
Col 4	D9	Column
Col 5	D10	Column

LCD Connection

LCD Pin	Arduino Pin
VCC	5V
GND	GND
SDA	A4 (Uno) / D18 (Mega)
SCL	A5 (Uno) / D19 (Mega)

Keypad Map

The code uses a custom 4x5 layout:

	Col 1	Col 2	Col 3	Col 4	Col 5
Row 1	/	*	-	+	=
Row 2	B	9	6	3	.
Row 3	A	8	5	2	0
Row 4	C	7	4	1	D

Usage Guide

1. Basic Math

Type the first number, press an operator (+, -, *, /), type the second number, and press =.

2. Modulo (Remainder)

Use the B key.

• Example: 10 B 3 =
• Result: 1 (because 10 divided by 3 leaves a remainder of 1).

3. Power & Root (The 'A' Key)

The A key enters a special mode.

1. Enter your first number (Base).
2. Press A.
3. The screen will show D+:Root D-:Power.
4. Select Mode:
   • Press D to toggle the sign.
   • Sign: + means Root (calculate $\sqrt[y]{x}$).
   • Sign: - means Power (calculate $x^y$).
5. Enter the second number (Exponent or Root degree).
6. Press =.

4. Negative Numbers

To make a number negative, type the number first, then press D.

• Example: To enter -5, type 5 then press D.

5. Clear

Press C to reset the calculator completely.