Arduino Sudoku Solver

An interactive Sudoku game and solver built for Arduino with a TFT touchscreen display. This project allows you to play, create, and solve Sudoku puzzles using a touch interface.

Note: This project is based on the Electronic Sudoku Game tutorial by TechKiwiGadgets on Instructables.

Features

• Play Mode: Load and play preloaded Sudoku puzzles with varying difficulty levels
• Puzzle Generator: Automatically generate new Sudoku puzzles with configurable difficulty
• Interactive Touch Interface: Use the touchscreen to input numbers directly into the grid
• Help System: Highlight conflicts and errors in red to assist with solving
• Auto Solver: Automated solver that attempts to solve puzzles using multiple algorithms
• Home Mode: Create your own puzzles from scratch or manually enter puzzles to solve

Hardware Requirements

• Arduino Uno R3 (or compatible)
• 2.8" TFT Touch LCD Screen (compatible with MCUFRIEND_kbv library)
• Touchscreen stylus (optional, for better precision)

Software Requirements

Arduino Libraries

The following libraries are required and can be installed via the Arduino Library Manager:

• MCUFRIEND_kbv - TFT LCD display driver
• Adafruit_GFX - Graphics core library
• TouchScreen - Touchscreen input handling

Installation

1. Install the required libraries using the Arduino IDE Library Manager:

   • Go to Sketch → Include Library → Manage Libraries
   • Search for and install:
     • MCUFRIEND_kbv
     • Adafruit_GFX
     • TouchScreen

2. Open the main sketch file sudoku_solver.ino in the Arduino IDE

3. Upload the code to your Arduino board

Configuration

Touchscreen Calibration

The touchscreen calibration values are defined in sudoku_solver.ino:

#define TS_MINX 934
#define TS_MAXX 149
#define TS_MINY 967
#define TS_MAXY 140

If your touchscreen coordinates are incorrect, you may need to adjust these values. The code includes test coordinate data that can be used for calibration.

Display Settings

• Display identifier: 0x9488 (ILI9488 controller)
• Screen rotation: Portrait mode (can be adjusted in setup())
• Color definitions can be modified if your display shows incorrect colors

Usage

Controls

The interface includes four main buttons:

1. HOME (Green): Clears the board and allows you to create your own puzzle or manually enter a puzzle to solve
2. PLAY (Yellow): Loads a preloaded puzzle or generates a new one. Cycles through 6 different puzzles
3. HELP (Magenta): Highlights conflicts in red for half a second to help identify errors
4. SOLVE (Blue): Attempts to automatically solve the current puzzle using the solver algorithms

Playing the Game

1. Press PLAY to load a puzzle
2. Touch any cell in the 9x9 grid to select it
3. Touch the same cell again to cycle through numbers 1-9 (or 0 to clear)
4. Use HELP to check for conflicts if you're unsure about your entries
5. Use SOLVE to let the computer solve the puzzle automatically

Puzzle Generation

The system includes a Sudoku puzzle generator that creates valid puzzles with configurable difficulty:

• Easy: 40 digits removed
• Medium: 50 digits removed
• Hard: 60 digits removed

Puzzles are generated using a recursive backtracking algorithm that ensures a valid solution exists.

Project Structure

sudoku_solver/
├── sudoku_solver.ino    # Main program file with setup and loop
├── sudoku_game.ino      # Game logic, puzzle loading, and solver algorithms
├── sudoku_generator.ino # Sudoku puzzle generator class and functions
├── screen.ino           # Display functions (drawing grid, buttons, refresh)
└── touch.ino            # Touchscreen input handling and cell value changes

Solver Algorithms

The solver implements several techniques:

1. Horizontal Rule: Eliminates possibilities based on solved cells in the same row
2. Vertical Rule: Eliminates possibilities based on solved cells in the same column
3. Panel Rule: Eliminates possibilities based on solved cells in the same 3x3 box
4. Reverse Solve: Identifies cells with only one remaining possibility
5. Unique Candidate: Finds cells where a number can only appear in one location within a box/row/column

Technical Details

Data Structure

The Sudoku grid is stored in a 2D array sudoku[82][14] where:

• Index 0: Solve flag (0 = unsolved, 1 = preloaded clue, 2 = solved/entered)
• Index 1: Display value (0-9)
• Index 2: Y coordinate for display
• Index 3: X coordinate for display
• Indices 4-12: Possible values (1-9) for constraint elimination
• Index 13: Panel/box identifier (1-9)

Touch Input

Touch coordinates are mapped to grid positions using a cell-based coordinate system. The touchscreen is debounced to prevent accidental multiple inputs.

Troubleshooting

Display Issues

• Wrong colors: Check the color definitions in the code (around line 24-32)
• Inverted display: Adjust the rotation in setup() (line 89)
• Touch not working: Recalibrate touch coordinates using the test data in the code

Solver Issues

• The solver may not complete all puzzles, especially very difficult ones
• Some puzzles may require manual intervention
• Use the HELP button to identify conflicts before solving

Credits

This project is based on the Electronic Sudoku Game tutorial by TechKiwiGadgets on Instructables.

License

This project is provided as-is for educational and personal use.

Contributing

Feel free to submit issues, fork the repository, and create pull requests for any improvements.

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Enjoy solving Sudoku puzzles!