#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Pin definitions for ultrasonic sensor
const int trigPin = 5;  // Trigger pin
const int echoPin = 18; // Echo pin

LiquidCrystal_I2C lcd = LiquidCrystal_I2C(0x27, 16, 2);

// Variables
float height = 0.0;    // in meters
float weight = 0.0;    // in kg
float bmi = 0.0;
long duration;
float distance;


void setup() {
  // Initialize Serial communication
  Serial.begin(115200);

  lcd.init();
  lcd.backlight();
  
  // Configure ultrasonic sensor pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  
  // Initial LCD display
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("BMI Calculator");
  delay(500);
}

float measureHeight() {
  // Clear trigger pin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  
  // Send 10μs pulse
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  // Measure the response
  duration = pulseIn(echoPin, HIGH);
  distance = (duration * 0.0343) / 2;
  float personHeight = (250 - distance) / 100;  // Convert cm to m
  return personHeight;
}

void calculateBMI() {
  bmi = weight / (height);
}

void displayBMI() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Height: ");
  lcd.print(height, 2);
  lcd.print("m");
  
  lcd.setCursor(0, 1);
  lcd.print("BMI: ");
  lcd.print(bmi, 1);
  
  Serial.print(bmi);
}

void loop() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Enter weight(kg):");
  
  // Wait for weight input from Serial
  while (!Serial.available()) {
    delay(100);
  }
  
  if (Serial.available() > 0) {
    weight = Serial.parseFloat();
    Serial.print("Weight entered: ");
    Serial.print(weight);
    Serial.println(" kg");
    
    // Measure height
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Measuring height");
    delay(100);
    
    height = measureHeight();
    
    Serial.print("Measured height: ");
    Serial.print(height);
    Serial.println(" m");
    
    // Calculate and display BMI
    calculateBMI();
    displayBMI();
    
    // Wait before next measurement
    delay(2000);
  }
}