// This code implements traffic lights behaviour on the crossing of two roads.
// Shift registers are used to save some digital pins on Arduino.
// Slightly strangely but mainly due to gradual development of the system
// each shift register has two car traffic lights, one for each road
// and one pedestrian traffic light, for each road connected. 


// Define the pins for the 74HC595 shift register 1
const int dataPin1 = 2;   // SER
const int clockPin1 = 3;  // SRCLK
const int latchPin1 = 4;  // RCLK

// Define the pins for the 74HC595 shift register 2
const int dataPin2 = 5;   // SER
const int clockPin2 = 6;  // SRCLK
const int latchPin2 = 7;  // RCLK


// Traffic light 1 states
const byte RED1 = 0b00000001;
const byte YELLOW1 = 0b00000010;
const byte GREEN1 = 0b00000100;

// Traffic light 2 states
const byte RED2 = 0b00001000;
const byte YELLOW2 = 0b00010000;
const byte GREEN2 = 0b00100000;

// Pedestrian trafic light 1 states
const byte REDP1 = 0b01000000;
const byte GREENP1 = 0b10000000;

// Pedestrian trafic light 2 states
const byte REDP2 = 0b01000000;
const byte GREENP2 = 0b10000000;


void setup() {
  // Initialize the shift register control pins as outputs
  pinMode(dataPin1, OUTPUT);
  pinMode(clockPin1, OUTPUT);
  pinMode(latchPin1, OUTPUT);

  pinMode(dataPin2, OUTPUT);
  pinMode(clockPin2, OUTPUT);
  pinMode(latchPin2, OUTPUT);

  // Initialize the traffic lights
  updateShiftRegister1(RED1 | GREEN2 | GREENP1);
  updateShiftRegister2(RED1 | GREEN2 | REDP2);
}

void loop() {
  // First traffic light: Green, Second traffic light: Red
  // First pedestrian traffic light: Red
  // Second pedestrian traffic light: Green
  updateShiftRegister2(GREEN1 | RED2 | REDP1);
  updateShiftRegister1(GREEN1 | RED2 | GREENP2);
  delay(120000); // 2 minutes = 120000 ms

  // First traffic light: Yellow, Second traffic light: Red
  // First pedestrian traffic light: Red
  // Second pedestrian traffic light: Red
  updateShiftRegister1(YELLOW1 | RED2 | REDP1);
  updateShiftRegister2(YELLOW1 | RED2 | REDP2);
  delay(5000); // 5 seconds = 5000 ms

  // First traffic light: Red, Second traffic light: Green
  // First pedestrian traffic light: Green
  // Second pedestrian traffic light: Red
  updateShiftRegister1(RED1 | GREEN2 | GREENP1);
  updateShiftRegister2(RED1 | GREEN2 | REDP2);
  delay(120000); // 2 minutes = 120000 ms

  // First traffic light: Red, Second traffic light: Yellow
  // First pedestrian traffic light: Red
  // Second pedestrian traffic light: Red
  updateShiftRegister1(RED1 | YELLOW2 | REDP1);
  updateShiftRegister2(RED1 | YELLOW2 | REDP2);
  delay(5000); // 5 seconds = 5000 ms
}

// Functions to update the shift registers
void updateShiftRegister1(byte data) {
  // Set latchPin low to prepare for data loading
  digitalWrite(latchPin1, LOW);

  // Shift out the data
  shiftOut(dataPin1, clockPin1, MSBFIRST, data);

  // Set latchPin high to store the data in the register
  digitalWrite(latchPin1, HIGH);
}

void updateShiftRegister2(byte data) {
  // Set latchPin low to prepare for data loading
  digitalWrite(latchPin2, LOW);

  // Shift out the data
  shiftOut(dataPin2, clockPin2, MSBFIRST, data);

  // Set latchPin high to store the data in the register
  digitalWrite(latchPin2, HIGH);
}