Difference between revisions of "F24: Tilt Maze"

Connectivity Table MP3 Decoder to Sj2 Board:

Hardware Interface

• **LED Matrix Display**: 13 GPIO channels on SJ2 microcontroller
• **Accelerometer (ADXL345)**: I2C communication on SJ2 microcontroller (SCL, SDA)
• **MP3 Decoder**: SPI communication using MOSI, CS, SCK on SJ2 microcontroller
• **Speaker**: AUX cord for audio output
• **Power Supply**: 5V/4A adapter for powering the LED matrix and SJ2 microcontroller

Software Design

• **LED Matrix:
  • 1. Initialized LED matrix connected pins to board IOs.
  • 2. Designed matrix driver for screen display by rendering maze patterns and player movements.

• **Accelerometer**:
  • 1. Initialized I2C communication for ADXL345 accelerometer.
  • 2. Configured accelerometer in measurement mode and set sensitivity to ±2g.
  • 3. Processed tilt data to calculate real-time player movement commands.

• **Mp3 Player**:
  • 1. Initialized using UART2.
  • 2. Set the device to the selected SD card and configured volume level.
  • 3. Played background music and sound effects based on game state.

Implementation

• **LED Matrix Driver Functions**:
• LED Matrix:
  • 1. Initialized LED matrix connected pins to board IOs.
  • 2. Designed matrix driver for screen display by reading an matrix.
  • 3. Designed pause menu, main menu and gameplay environment for different states of game.
  • 4. Used GPIO pins as buttons as controls in main menu

• **Accelerometer Driver**:
  • 1. accelerometer_init: Configures the ADXL345 accelerometer with ±2g sensitivity and sets up I2C communication with semaphores for thread safety
  • 2. accelerometer_task: Periodically reads acceleration data, applies smoothing, and updates player position based on tilt movements

// Add acceleration smoothing static int16_t last_x = 0; static int16_t last_y = 0; const float smoothing_factor = 0.7f; // Increased for better responsiveness

void accelerometer_init(void) {

 // Initialize I2C at 400kHz for faster response
 i2c__initialize(I2C__2, 400 * 1000, 96 * 1000 * 1000UL, &binary_sem_memory, &mutex_memory);
 // Create mutex for thread-safe movement
 movement_mutex = xSemaphoreCreateMutexStatic(&mutex_memory);

 // Configure ADXL345 accelerometer
 i2c__write_single(I2C__2, ADXL345_WRITE, REG_DATA_FORMAT, 0x00); // ±2g range
 i2c__write_single(I2C__2, ADXL345_WRITE, REG_POWER_CTL, 0x08);   // Measurement mode

 // Initialize smoothing variables
 last_x = 0;
 last_y = 0;

}

• Maze Logic:
  • 1. `get_maze_layout`: Retrieves the maze pattern for the current level
  • 2. `is_wall_at`: Checks if a specific position in the maze contains a wall, used to constrain player movement
  • 3. `is_goal_at`: Determines if the player has reached the maze's goal position to proceed to the next level

• **Game Logic**:
  • 1. set_player_to_start : Resets the player position to the starting point of the current level
  • 2. handle_collisions: Detects collisions with walls, traps, and goals, triggering state changes like `GAME_STATE_GAME_OVER` or GAME_STATE_LEVEL_UP
  • 3. change_game_state: Manages game states such as `GAME_STATE_TITLE`, `GAME_STATE_PLAYING`, and `GAME_STATE_WIN`, and handles music transitions

switch (new_state) {

 case GAME_STATE_TITLE:
   stop_gameplay_music();
   mp3_decoder__play_song_at_index(SOUND_TITLE);
   enable_movement(false);
   break;

 case GAME_STATE_PLAYING:
   start_gameplay_music();
   enable_movement(true);
   break;

 case GAME_STATE_LEVEL_UP:
   stop_gameplay_music();
   mp3_decoder__play_song_at_index(SOUND_LEVELUP);
   enable_movement(false);
   break;

 case GAME_STATE_GAME_OVER:
   stop_gameplay_music();
   mp3_decoder__play_song_at_index(SOUND_LOSE);
   enable_movement(false);
   break;

 case GAME_STATE_WIN:
   stop_gameplay_music();
   mp3_decoder__play_song_at_index(SOUND_WIN);
   enable_movement(false);
   break;
 }

}

• **MP3 Decoder**:
  • 1. mp3_decoder__init: Initializes the MP3 decoder, sets the default volume, and selects the storage device
  • 2. mp3_decoder__play_song_at_index: Plays a specific song based on its index in single-cycle mode
  • 3. mp3_decoder__play_song_with_mode: Allows playback in loop or single-cycle mode, depending on the game state
  • 4. mp3_decoder__stop_playback: Stops any active song playback
  • 5. mp3_decoder__volume_set_level: Adjusts the volume level of the MP3 decoder

typedef enum {

 mp3_decoder__next_song = 0x01,
 mp3_decoder__prev_song = 0x02,
 mp3_decoder__play_at_index = 0x03,
 mp3_decoder__play_loop = 0x08, // Added loop command
 mp3_decoder__set_volume = 0x06,
 mp3_decoder__select_device = 0x09,
 mp3_decoder__reset = 0x0C,
 mp3_decoder__stop = 0x16, // Added stop command

} mp3_decoder__commands_e;

// Added playback mode enum typedef enum { MP3_PLAY_ONCE, MP3_PLAY_LOOP } mp3_playback_mode_t;

Testing & Technical Challenges

The most challenging part of the Tilt Maze game was the integration and calibration of the accelerometer. Reading accurate tilt data and translating it into smooth, responsive movements for the game character required careful implementation. Additionally, ensuring the player's movement was constrained within the maze boundaries while avoiding unintended behavior added complexity.

Bug/Issue Name

Conclusion

Building the Tilt Maze game on a microcontroller proved to be a rewarding and challenging experience. Developing custom drivers for the accelerometer, LED matrix, and MP3 decoder required a deep understanding of embedded systems. Implementing FreeRTOS tasks to handle concurrent updates for accelerometer input, game logic, and display rendering added complexity but ensured smooth and responsive gameplay. One of the most challenging aspects was achieving accurate and stable accelerometer readings for tilt detection, which required calibration, noise filtering, and careful logic for player movement.

Throughout the project, we encountered various issues, including synchronization conflicts, noisy sensor data, and priority balancing in FreeRTOS. These challenges taught us the importance of debugging, modular design, and leveraging RTOS APIs effectively. As embedded engineers, we learned that creating a system from scratch involves meticulous attention to both hardware and software integration.

In the end, we successfully implemented a fun and interactive game that showcases the power of embedded systems. Future improvements could include adding a scoring system, dynamic maze generation, and more refined accelerometer controls to further enhance gameplay.

Project Video

[Watch the Tilt Maze game demo]

Project Source Code

https://gitlab.com/first892736/tilt-maze-group-2

References

Acknowledgement

Special thanks to Mr. Preet Kang for his lessons and detailed-documentation website on microcontrollers.

References Used

• 1. Mp3 user manual: https://usermanual.wiki/Pdf/Serial20MP320Player20v10120Manual.2117229468/view
• 2. LPC40xx_FreeRtos Github: https://gitlab.com/sjtwo-c-dev/sjtwo-c

Appendix

• 1. LPC40xx_FreeRtos Github: https://gitlab.com/sjtwo-c-dev/sjtwo-c
• 2. FreeRTOS: https://www.freertos.org/a00116.html