//Connect the OLED Display to the Arduino Nano:
//OLED VCC to Arduino 5V
//OLED GND to Arduino GND
//OLED SDA to Arduino A4 (analog pin 4)
//OLED SCL to Arduino A5 (analog pin 5)


#include <Wire.h>
#include <Adafruit_SSD1306.h>

#define OLED_RESET    -1
Adafruit_SSD1306 display(OLED_RESET);

#define TRIG  2  // Trig pin of ultrasonic sensor connected to D2
#define ECHO  3 // Echo pin of ultrasonic sensor connected to D3

#define R  9   // Red LED connected to D9
#define G 10  // Green LED connected to D10
#define B 11  // Blue LED connected to D11

int distance = 0;

void setup() {
  Serial.begin(9600); //slow baud rate of 9600 bits per second (bps).
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(R, OUTPUT);
  pinMode(G, OUTPUT);
  pinMode(B, OUTPUT);

  display.begin(SSD1306_WHITE, 0x3C); // Address 0x3C for 128x32
  display.display();
  delay(2000);
  display.clearDisplay();
}

void loop() {
  // Measuring the distance
  distance = getDistance();

  // Display the distance on the OLED screen
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0,0);
  display.print("Distance: ");
  display.print(distance);
  display.print(" mm");
  display.display();

  // Control of the LEDs based on distance
  if (distance >= 350) {
    digitalWrite(R, HIGH);
    digitalWrite(G, LOW);
    digitalWrite(B, LOW);
  }
   else if (distance >= 200 && distance < 350) {
    digitalWrite(R, LOW);
    digitalWrite(G, HIGH);
    digitalWrite(B, LOW);
  } 
  else if (distance >= 0 && distance < 200) {
    digitalWrite(R, LOW);
    digitalWrite(G, LOW);
    digitalWrite(B, HIGH);
  }

  delay(100); // can be adjusted 
}

 int getDistance() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  return pulseIn(ECHO, HIGH) * 0.034 / 2;
}