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

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define SoundSpeed 0.034 // in cm/us


const int trigger = 27;
const int echo = 26;

long duration;
float distance;



// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define NUMFLAKES     10 // Number of snowflakes in the animation example

#define LOGO_HEIGHT   16
#define LOGO_WIDTH    16
static const unsigned char PROGMEM logo_bmp[] =
{ B00000000, B11000000,
  B00000001, B11000000,
  B00000001, B11000000,
  B00000011, B11100000,
  B11110011, B11100000,
  B11111110, B11111000,
  B01111110, B11111111,
  B00110011, B10011111,
  B00011111, B11111100,
  B00001101, B01110000,
  B00011011, B10100000,
  B00111111, B11100000,
  B00111111, B11110000,
  B01111100, B11110000,
  B01110000, B01110000,
  B00000000, B00110000 };

void setup() {
  Serial.begin(115200);
  pinMode(trigger, OUTPUT);
  pinMode(echo,INPUT);

  // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { 
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }

  // Show initial display buffer contents on the screen --
  // the library initializes this with an Adafruit splash screen.
  //display.display();
  //delay(2000); // Pause for 2 seconds

  // Clear the buffer
  display.clearDisplay();

  //Display Text
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0, 0);
  display.println("Welcome");
  display.setCursor(0, 10);
  display.println("To");
  display.setCursor(0, 20);
  display.println("HCSR04 ESP32 OLED");  
  display.setCursor(0, 30);
  display.println("Tutorial");  
  display.setCursor(0, 40);
  display.println("RPW1 LAB");    
  display.display(); 
  delay(2000);
  display.clearDisplay();

}
void loop() {
digitalWrite(trigger,LOW);
delayMicroseconds(2);
digitalWrite(trigger,HIGH);
delayMicroseconds(10);
digitalWrite(trigger,LOW);

duration = pulseIn(echo,HIGH);
distance = duration * SoundSpeed /2;
Serial.println("Distance in cm: " + String(distance) );

 display.setCursor(20, 20);
 display.println("Distance in cm: ");  
 display.setCursor(60, 40);
 display.print(distance);
 display.display();
 delay(2000);
 display.clearDisplay();

}