🤖 MSP432 Autonomous Maze Solver

Autonomous navigation system designed for a differential drive robot. This project implements a robust Wall-Following Algorithm using IR distance sensors and a Real-Time Proportional Controller to correct trajectory errors on the fly.

Built from scratch in C without high-level abstractions, interacting directly with registers and implementing a custom UART Driver for Dynamixel actuators.

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🎥 Demo

(The robot continuously adjusts its distance to the wall using P-Control logic)

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🧠 Algorithmic Logic (Flowcharts)

1. Main Control Loop & State Machine

The system features a safety-first "Arming Sequence". The robot does not move until the mode is activated (Center Button) and a direction is selected.

👁️ Click to expand Main Logic Diagram

graph TD
    Start([Start System]) --> Init[Init UART, Timers & Interrupts]
    Init --> Idle{Wait for Input}
    
    Idle -- "Center Button" --> Arm[Mode ENABLED<br/>Wait for Direction]
    Arm -- "Left/Right Joystick" --> SetDir[Set Direction Flags]
    SetDir --> CheckLoop{Check Loop Condition}
    
    CheckLoop -- "Flags=True & Mode=True" --> Algorithm[Execute Wall Follower]
    Algorithm --> CheckJoy{Joystick Moved?}
    
    CheckJoy -- "YES (Emergency Stop)" --> Stop[STOP Robot & Reset Flags]
    Stop --> Idle
    
    CheckJoy -- NO --> CheckLoop
    
    style Start fill:#f9f,stroke:#333,stroke-width:2px
    style Stop fill:#ffaaaa,stroke:#333,stroke-width:2px

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2. Wall Following Logic (Right Hand Rule)

Complex decision-making process involving Proportional Error Correction for straight lines and specific sub-routines for corners and dead-ends.

👁️ Click to expand Algorithm Diagram

graph TD
    Start([Start Algorithm]) --> Read[Read All Sensors]
    Read --> Front{Wall in Front?}
    
    %% BRANCH: WALL IN FRONT
    Front -- YES --> RightClose{Right Wall Close?}
    RightClose -- YES --> Rot90[Rotate 90 Left]
    RightClose -- NO --> TurnLeft[Turn Left]
    TurnLeft --> Advance1[Advance]
    
    Rot90 --> DetectRight{Detect Right Wall?}
    DetectRight -- YES --> Merge((Continue))
    
    %% RECOVERY MODE (Lost Wall)
    DetectRight -- NO --> LargeRot[Wide Rotation<br/>Advance + Turn Right]
    LargeRot --> Read2[Read Sensors]
    Read2 --> FrontVeryClose{Front Wall<br/>Very Close?}
    
    FrontVeryClose -- YES --> Rot180[Rotate 180]
    FrontVeryClose -- NO --> DetectRight
    Rot180 --> DetectRight
    
    %% BRANCH: NO WALL IN FRONT (Proportional Control)
    Front -- NO --> Calc["Calculate Error<br/>(Ideal - Actual)"]
    Calc --> ErrBig{"Error > 3<br/>(Too Far)"}
    
    ErrBig -- YES --> TurnRight[Turn Right]
    ErrBig -- NO --> ErrSmall{"Error < -3<br/>(Too Close)"}
    
    ErrSmall -- YES --> TurnLeft2[Turn Left]
    ErrSmall -- NO --> Advance2[Advance Fast]
    
    TurnRight --> Advance3[Advance]
    TurnLeft2 --> Advance3
    Advance2 --> Merge
    Advance3 --> Merge
    
    Merge --> Read

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🏗️ Technical Architecture

1. Hardware Abstraction Layer (HAL)

The code is structured to separate business logic from hardware specifics:

• main.c: High-level decision making and state management.
• robot_control.c: Low-level driver implementation. Direct manipulation of P3.2/P3.3 for UART and Timer_A0/A1 for precise timing.

2. Custom Protocol Implementation

Instead of using a pre-built library, a custom driver was written to communicate with the Dynamixel AX-12A motors via UART Half-Duplex.

• Packet Construction: Manually assembling the byte frame (Header, ID, Length, Instruction, Checksum).
• Error Handling: Implementation of TxPacketSegur to retry transmission upon checksum failures.

3. Memory & Resource Management

• Efficient Polling: Optimized sensor reading cycles to avoid blocking the CPU.
• Bitwise Operations: Extensive use of bit masking for register configuration (NVIC, GPIO) to minimize memory footprint.

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🛠️ Hardware Stack

• Microcontroller: TI MSP432P401R (ARM Cortex-M4F)
• Actuators: Dynamixel AX-12A (Smart Serial Servos)
• Sensors: IR Distance Sensors (Sharp GP2Y0A21YK)
• Interface: Nokia 5110 LCD & Joystick Shield

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💻 How to Flash

1. Import the source files (.c, .h) into Code Composer Studio.
2. Ensure the target is set to MSP432P401R.
3. Build and Flash via USB Debugger.