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

#define trigPin 2
#define echoPin 3

#define OLED_RESET 4
Adafruit_SSD1306 display(OLED_RESET);

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C); 
  display.clearDisplay();
}

void loop() {
  float duration;
  float distance_cm;
  float distance_in;
  float distance_mm; 

  digitalWrite(trigPin, LOW); 
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);

  distance_cm = (duration / 2) / 29.1;
  distance_in = (duration / 2) / 73.914;
  distance_mm = duration / 2 * 0.343; 

  display.setCursor(25, 0); 
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.println("Distance Meter");

  display.setCursor(10, 20); 
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.println(distance_cm);
  display.setCursor(90, 20);
  display.setTextSize(2);
  display.println("cm");

  display.setCursor(10, 45); 
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.println(distance_in);
  display.setCursor(90, 45);
  display.setTextSize(2);
  display.println("in");

  display.setCursor(10, 70); 
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.println(distance_mm);
  display.setCursor(90, 70);
  display.setTextSize(2);
  display.println("mm");

  display.display();

  delay(500);
  display.clearDisplay();

  Serial.println(distance_cm);
  Serial.println(distance_in);
  Serial.println(distance_mm);
}