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

// OLED settings
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Ultrasonic sensor pins
#define TRIG_PIN 18
#define ECHO_PIN 19

void setup() {
  Serial.begin(115200);

  // Initialize ultrasonic pins
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  // Initialize I2C
  Wire.begin(4, 5);  // SDA = GPIO4, SCL = GPIO5

  // Initialize OLED display
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // 0x3C is the common I2C address
    Serial.println(F("SSD1306 allocation failed"));
    for (;;); // Don't proceed, loop forever
  }

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0,0);
  display.println("Ultrasonic Ready");
  display.display();
}

void loop() {
  long duration;
  float distance_cm;

  // Trigger the ultrasonic pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read echo time
  duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate distance in cm
  distance_cm = duration * 0.0343 / 2;

  // Print to Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");

  // Show on OLED
  display.clearDisplay();
  display.setTextSize(2);
  display.setCursor(0,0);
  display.print(distance_cm, 1);
  display.println(" cm");
  display.display();

  delay(500); // Update every half second
}