/*
 * HC-SR04 example sketch
 *
 * https://create.arduino.cc/projecthub/Isaac100/getting-started-with-the-hc-sr04-ultrasonic-sensor-036380
 *
 * by Isaac100
 */
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);


const int trigPin = 9;
const int echoPin = 8;

float distance1;
float t1;
float distance2;
float t2;
float speed;

float sonicRead ()
{
   digitalWrite(trigPin, HIGH);
   delayMicroseconds(10);
   digitalWrite(trigPin, LOW);
 
   unsigned long duration = pulseIn(echoPin, HIGH);
   return duration * 0.034 / 2;
}

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
  lcd.begin(2,16,LCD_5x8DOTS);      // pocetak rada display-a
  lcd.backlight(); 
}

void loop() {
  
distance1 = sonicRead();
t1 = millis();
delay(1000);
distance2 = sonicRead();
t2 = millis();
speed = (distance2 - distance1)*1000 / ( t2 - t1);
  lcd.setCursor(0,0);
  lcd.print("Distance: ");
  lcd.println(distance2);
  lcd.setCursor(0,1);
  lcd.print("Speed: ");
  lcd.println(speed);
  delay(10);
}