🚦 Traffic Control System

This project implements a smart Traffic Light Control System on STM32 microcontroller, desgined to manage a 4-way intersection. The system intelligently controls 4 traffic lights, dynamically adjusting light states based on real-time vehicle detection and traffic density.

By leveraging external interrupts, queue-based scheduling, and SysTick timer, the controller ensures efficient traffic flow, minimal waiting times, and safe transitions between lights.

Documentation: The project includes comprehensive Doxygen documentation covering modules, functions, classes and detailed usage.
👉 Explore the generated docs: Doxygen Documentation

🔑 Key Features

1. Event-Driven Architecture · Low-Power · Interrupts

• The system remains in a low-power idle state until a vehicle is detected, reducing unnecessary CPU usage.
• All events are interrupt-driven, ensuring responsive traffic management without continous polling.

2. GPIO External Interrupts (EXTI) · GPIO · Interrupts · Vehicle Detection

• Each traffic lane has a button-simulated vehicle sensor connected to a GPIO pin.
• External interrupts immediately detect vehicle presence, triggering the control logic efficiently.

3. Efficient Queue System · Circular Queue · Scheduling

• Uses a circular queue to manage requests for green signals from different lanes.
• Guarantees first-come, first-served priority while preventing lost requests.
• Optimized for multiple simultaneous requests.

4. Dynamic Signal Timing · Adaptive Control · Timing

• Adjust green signal duration based on the number of vehicles detected.
  Example: 1 car -> 2 seconds, 2 cars -> 3 seconds, >3 cars -> 5 seconds.
• Ensures shorter waits for low-traffic lanes and longer green phases for high-traffic lanes.

5. SysTick Timer · Timers · Scheduling · Precision

• Implements a millisecond-precision timer for scheduling light transitions and timeouts.
• Enables precise delay management and time-based vehicle detection logic.

6. UART Communication · UART · Debugging · Monitoring

• UART outputs provide a detailed, real-time log of system operations, enabling effective debugging, state monitoring, and timing analysis.
• Displays traffic light states, vehicle counts, transitions, and timing information in real-time.

7. LED Traffic Light Control · GPIO · Embedded Sytems

• Uses GPIO outputs to drive LEDs representing traffic lights (RED, GREEN, YELLOW).
• Provides accurate visual simulation of real-world trffic lights.

8. Bare-Metal Firmware · Direct Register Access · Embedded · C Programming

• Written entirely in C, using direct register access for maximum efficiency.
• No operating system overhead; fully bare-metal for predictable timing and low latency.

9. Modular Design Architecture · Modularity · Maintainability

• Firmware divided into clear modules: controller, lights, exti, queue, uart, systick encouraging reuse and scalability for future traffic projects.
• Each module handles a specific responsibility, making code easy to maintain and extend.

10. Doxygen Documentation · Documentation · Maintainability

• Fully documented using Doxygen with clear function, module, and data structure description.
• Generate browsable HTML documentation published via GitHub Pages from the docs/ directory.

🏗 System Architecture

                                     |  |  │  |  |
                          south-bound|  |  │  |  |
                            traffic  |  |⬇️│  |⬆️| 
                                     |  |  │  |  |
                                     |⬇️|  │⬆️|  |
                                     ── ── ── ── ─ 
                                      🚥 
               _ _ _ _ _ _ _ .       Light 2           ._ _ _ _ _ _ _ _ _ west-bound
               _ _ _ ⬅️ _  _ |                       🚦|_⬅️ _ _ _ _ _ _ _   traffic
               ___________⬅️_|                 Light 3 |_______⬅️________
    east-bound _ _ _➡️ _ _ _ |🚦                       |_➡️ _ _ _ _ _ _ _
      traffic  _ _ _ _ _➡️ _ |Light 1                  |_ _ _ _ ➡️_ _ _ _
                                             🚥 Light 4
                                     ── ── ── ── ─ 
                                     |⬇️|  │  |⬆️|
                                     |  |  │  |  | north-bound 
                                     |  |⬇️│⬆️|  |   traffic
                                     |  |  │  |  |
                                     |  |  │  |  |

🔄 Traffic Light Synchronization

Light 1 and Light 3 are synchronized, operating in tandem to manage east-west traffic flow.
Light 2 and Light 4 are synchronized, controlling north-south traffic flow.

💡 Example Serial Terminal Output

other outputs above...
Light 1-3: RED (east-west traffic stopped)   
Light 2-4: GREEN (north-south traffic allowed) 

Light 1 car detected: 1
Light 1 car detected: 2
Light 1 car detected: 3

Light 2-4: YELLOW (caution, changing soon)
Light 2-4: RED (north-south traffic stopped)
Light 1-3: GREEN (east-west traffic allowed)
... continues with other outputs

🛠️ Tools & Software

🕹️ Microcontroller Development

• VS Code - Primary development environment for STM32 firmware, used for editing, building, and debugging.
• OpenOCD - Used for flashing firmware and debugging the STM32 over SWD.
• Makefile - Manages compilation, linking, and build automation for the project.

⚙️ Hardware

• STM32 MCU - Microcontroller responsible for controlling traffic light logic and timing.
• RGB LEDs - Used to simulate the traffic lights.
  • Used Red and Green LEDs; Yellow is achieved by activating both red and green LEDs simultaneously.
• Resistors - Limit LED current and protect GPIO pins.
• Breadboards - Enables rapid prototyping and testing of the traffic light system.

⛓️ Hardware Connection

Traffic Light LED Connections

• LEDs are configured in an active-low setup, with the common anode connected to ground.
• Red and green channels driven by dedicated GPIO outputs.
• Yellow state achieved by simultaneously activating both red and green channels.

Button Connections:

• Tactile push buttons are connected to GPIO input pins configured with internal pull-up resistors.
• Pressing a button pulls the input low, generating a GPIO external interrupt (EXTI) used to simulate vehicle detection.

📍 Pin Assignments

LIGHT	RED	GREEN	BUTTON
Light 1	PB10	PB4	PC10
Light 2	PB5	PB3	PC11
Light 3	PB2	PB1	PC12
Light 4	PB14	PB13	PC13

Demo