RTOS Micromouse

A real-time operating system (FreeRTOS) based micromouse robot that solves line-following mazes using state machines and task-based concurrency.

Overview

This project implements a sophisticated maze-solving robot using:

• Arduino Nano (ATmega328P) microcontroller
• FreeRTOS for multitasking and real-time control
• QTR Sensors for line detection (8-sensor array)
• TB6612 Motor Driver for motor control
• State Machine Architecture for robot behavior management

Features

• ✅ Line following with PID control
• ✅ Automatic sensor calibration
• ✅ Left-hand and right-hand maze solving rules
• ✅ Intersection detection and turn execution
• ✅ Path optimization and simplification
• ✅ Recovery mechanism for lost line detection
• ✅ Watchdog task for timeout monitoring
• ✅ Multi-threaded task scheduling with FreeRTOS

Hardware Setup

Pin Definitions

Motor Control (TB6612):
- AIN1: Pin 5
- AIN2: Pin 4
- PWMA: Pin 3
- BIN1: Pin 6
- BIN2: Pin 8
- PWMB: Pin 9

Sensors:
- QTR-8 Array: A0-A7 (Analog Pins)

Control Switches:
- SW1 (Start/Restart): Pin 10
- SW2 (Left Rule): Pin 11
- SW3 (Right Rule): Pin 12

Indicators:
- LED: Pin 7

Wiring

• Connect TB6612 motor driver to specified pins
• Connect 8-sensor QTR array to analog pins A0-A7
• Connect switches with pull-up resistors to digital pins
• Connect 2 DC motors to motor driver outputs

Software Setup

Requirements

• PlatformIO (recommended) or Arduino IDE
• Arduino Framework
• Dependencies:
  • QTRSensors (v4.0.0+)
  • FreeRTOS (feilipu/FreeRTOS v10.5.1+)
  • Arduino core libraries

Build & Upload

# Install dependencies
platformio lib install

# Build the project
platformio run

# Upload to Arduino Nano
platformio run --target upload

# Monitor serial output
platformio device monitor --baud 9600

Operation

States

1. IDLE: Waiting for calibration command
2. CALIBRATING: Swinging left/right to calibrate sensors
3. EXPLORING: Solving the maze following selected rule
4. RECOVERY: Recovering when line is lost
5. FINISHED: Maze solved, ready for optimized run

Workflow

1. Power on the robot
2. Press SW1 to start calibration
3. Robot swings left/right to calibrate sensor thresholds
4. Press SW2 for left-hand rule or SW3 for right-hand rule
5. Robot explores and solves the maze
6. LED indicates status (blinking = calibrating/exploring, solid = finished)

Task Structure

• StateMachine Task (Priority 2): Executes state handlers every 50ms
• Watchdog Task (Priority 3): Monitors for timeouts and hangs

PID Control Parameters

kp = 0.161  // Proportional gain
kd = 0.54   // Derivative gain
BaseSpeed = 230
MaxSpeed = 255

Memory Usage

• Flash: 67.8% (20834 / 30720 bytes)
• RAM: 74.2% (1519 / 2048 bytes)

Serial Output

The robot sends debug information at 9600 baud:

• State transitions
• Sensor calibration values
• Maze solution path
• Error messages and warnings

Troubleshooting

• Robot spins in place: Check sensor wiring and calibration
• Motor not moving: Verify motor driver pins and power supply
• Poor line following: Adjust PID constants and sensor thresholds
• Timeout errors: Increase timeout values or check line continuity

License

See LICENSE file for details.