# Crossroad Traffic Light Controller

Arduino/ESP32 project for controlling a simple two-way crossroad traffic light system with pedestrian buttons.

The sketch is in `crossroad.ino`.

## Features

- Controls North/South and East/West traffic lights.
- Uses two pedestrian buttons.
- Runs with a non-blocking `millis()` state machine.
- Prints state changes and countdown logs to the Serial Monitor.
- Uses button debounce to avoid repeated false presses.

## Hardware

This project is written for an ESP32.

### Traffic Light Pins

| Direction | Color  | GPIO |
| --- | --- | --- |
| North/South | Red    | 23 |
| North/South | Yellow | 22 |
| North/South | Green  | 21 |
| East/West | Red    | 19 |
| East/West | Yellow | 18 |
| East/West | Green  | 5 |

### Pedestrian Button Pins

| Button | GPIO |
| --- | --- |
| Pedestrian button 1 | 32 |
| Pedestrian button 2 | 33 |

## Wiring Notes

### LEDs

The code uses active-low LEDs:

```cpp
const int LED_ON  = LOW;
const int LED_OFF = HIGH;
```

That means an LED turns on when the ESP32 pin is `LOW`.

Typical wiring:

```text
3.3V -> resistor -> LED -> GPIO pin
```

If your LEDs are wired from GPIO to resistor to GND, the lights may behave inverted.

### Buttons

The pedestrian buttons use `INPUT_PULLUP`:

```cpp
pinMode(PED_BTN_1, INPUT_PULLUP);
pinMode(PED_BTN_2, INPUT_PULLUP);
```

Each button should be wired like this:

```text
GPIO 32 -> button -> GND
GPIO 33 -> button -> GND
```

When the button is not pressed, the pin reads `HIGH`.
When the button is pressed, the pin connects to GND and reads `LOW`.

## Timing

| Event | Duration |
| --- | --- |
| Normal green light | 15 seconds |
| Normal yellow light | 3 seconds |
| Wait after pedestrian button press | 3 seconds |
| Pedestrian both-yellow phase | 3 seconds |
| Pedestrian both-red phase | 10 seconds |
| Button debounce | 50 milliseconds |

## Normal Traffic Flow

The normal traffic cycle is:

```text
NS green, EW red
NS yellow, EW red
EW green, NS red
EW yellow, NS red
repeat
```

## Pedestrian Flow

When either pedestrian button is pressed:

1. The request is registered.
2. The controller waits 3 seconds.
3. Both directions turn yellow.
4. After 3 seconds, both directions turn red.
5. After 10 seconds, the controller resumes the traffic state that was active when the button was pressed.

## Serial Monitor

Open the Serial Monitor at:

```text
115200 baud
```

Example logs:

```text
STATE: NS GREEN, EW RED
TIME BEFORE CHANGE (NS GREEN, EW RED): 15 sec
TIME BEFORE CHANGE (NS GREEN, EW RED): 14 sec
PEDESTRIAN REQUEST REGISTERED
PEDESTRIAN: will resume NS GREEN, EW RED
PEDESTRIAN: both yellow starts in 3 sec
STATE: BOTH YELLOW
TIME BEFORE CHANGE (BOTH YELLOW): 3 sec
STATE: BOTH RED
TIME BEFORE CHANGE (BOTH RED): 10 sec
STATE: NS GREEN, EW RED
```

## Uploading

1. Open `crossroad.ino` in the Arduino IDE.
2. Select your ESP32 board.
3. Select the correct USB port.
4. Upload the sketch.
5. Open Serial Monitor at `115200` baud to see logs.