Space Invaders on ATmega1284

A real-time Space Invaders game built in C/C++ for the ATmega1284. The project uses a cooperative (synchronous) task scheduler to keep gameplay responsive while coordinating graphics, input, score/lives output, and sound effects.

Overview

This project demonstrates how to build a small game loop on resource-constrained hardware by splitting work across periodic tasks:

• Read joystick input
• Update player/projectile/enemy state
• Render frames to the SPI LCD
• Update score/lives output
• Drive PWM sound effects

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Hardware Architecture

flowchart LR
    MCU[ATmega1284 MCU]
    LCD[HiLetgo 1.44 in <br> ST7735 SPI LCD]
    JOY[Joystick Module <br> ADC X/Y + Button]
    LED[2x16 LED Display <br> Score + Lives]
    BUZ[Passive Buzzer <br> PWM Output]

    MCU -- SPI --> LCD
    JOY -- Analog + Digital --> MCU
    MCU -- GPIO --> LED
    MCU -- Timer/PWM --> BUZ

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Main Peripherals

• Display: ST7735-based 1.44" SPI LCD for rendering gameplay.
• Input: Joystick for left/right movement and up for firing. Button for hard restart.
• Output: LED display for score and lives.
• Audio: Passive buzzer driven with PWM patterns.

Wiring Schematic

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16 x 2 LCD Display

The LCD is wired for a standard 4-bit data interface.

Arduino Pin	LCD Pin Label	Function	Connection Type
GND	VSS	Ground	Ground Rail
5V	VDD	Logic Power	Power Rail
-	VO	Contrast	Potentiometer (Wiper)
D2	RS	Register Select	Digital Signal
GND	RW	Read/Write	Ground Rail
D3	E	Enable	Digital Signal
D4	D4	Data Bit 4	Digital Signal
D5	D5	Data Bit 5	Digital Signal
D6	D6	Data Bit 6	Digital Signal
D7	D7	Data Bit 7	Digital Signal
5V	A	Display Power	Power Rail
GND	K	Ground	Ground Rail

HiLetgo Module (SPI LCD display)

This module utilizes the high-speed SPI pins for game rendering.

Arduino Pin	Module Pin Label	Function
5V	LED	LED
D13	SCK	Serial Clock
D11	SDA	Serial Data (MOSI)
D8	AO	Data/Command Select
D10	RESET	Module Reset
D12	CS	Chip Select
GND	GND	Ground Rail
5V	VCC	Logic Power

Joystick

Arduino Pin	Module Pin Label	Function
GND	GND	Ground
5V	5V	Power
A1	VRX	Serial Data (MOSI)
A2	VRY	Data/Command Select
A0	SW	Module Reset

Other Components

Arduino Pin	Component
A5	Button
D9	Buzzer

Software / Task Flow

The program runs as a scheduled set of finite-state-machine-style tasks.

flowchart TD
    Start([Power On / Reset]) --> Init[Initialize peripherals<br>SPI, ADC, Timers, PWM, LCD]
    Init --> Scheduler[Start synchronous scheduler]

    Scheduler --> T1[Task: Read Input]
    Scheduler --> T2[Task: Update Game State]
    Scheduler --> T3[Task: Collision & Rules]
    Scheduler --> T4[Task: Render Frame]
    Scheduler --> T5[Task: Update Score/Lives]
    Scheduler --> T6[Task: Audio Control]

    T1 --> T2
    T2 --> T3
    T3 --> T4
    T4 --> T5
    T5 --> T6
    T6 --> Scheduler

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Game State Flow

stateDiagram-v2
    [*] --> Boot
    Boot --> Menu
    Menu --> Playing: Start input
    Playing --> Playing: Move / Shoot / Spawn / Collide
    Playing --> Win: All enemies cleared
    Playing --> Lose: Lives == 0
    Win --> Menu: Restart
    Lose --> Menu: Restart

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Project Structure

.
├── src/
│   └── arein015_main.cpp      # Main game loop, scheduler, gameplay logic
├── include/
│   ├── st7735.h               # LCD driver interface
│   ├── spiAVR.h               # SPI utilities
│   ├── timerISR.h             # Timer/scheduler timing support
│   ├── analogHelper.h         # ADC / joystick helpers
│   ├── LCD.h                  # LCD helper utilities
│   └── serialATmega.h         # Serial debug support
├── platformio.ini             # Build configuration
└── README.md

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Build and Upload

Option 1: PlatformIO (recommended)

1. Install PlatformIO.
2. Connect your ATmega1284 programming setup.
3. Build:

   pio run

4. Upload:

   pio run -t upload

Option 2: AVR toolchain

• Compile with your AVR-GCC setup and flash using your preferred uploader.

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How to Play

1. Power on the system.
2. Use the joystick to move the player ship.
3. Trigger shoot input to fire projectiles.
4. Eliminate enemies while avoiding hits.
5. Watch score/lives on the LED display.
6. Listen for event-based buzzer feedback (shoot, win, lose).

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Why This Project Is Useful

• Demonstrates real-time embedded scheduling.
• Shows practical SPI graphics on constrained MCUs.
• Integrates mixed I/O: ADC, GPIO, PWM, timers, and display control.
• Good reference for embedded game architecture and classroom demos.

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License

This project is intended for educational and demonstration use.