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

// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Analog input pin for voltage measurement
const int voltagePin = A0;
// Reference voltage (usually 5V for Arduino, but measure for accuracy)
const float referenceVoltage = 5.0;
// Voltage divider ratio if you're using one (set to 1 for direct measurement)
const float voltageDividerRatio = 1.0;

void setup() {
  // Initialize the I2C LCD
  lcd.init();
  // Turn on the backlight
  lcd.backlight();
  
  // Print a startup message
  lcd.print("Voltage Meter");
  delay(1000);
  lcd.clear();
  
  // Configure the analog reference (DEFAULT is usually 5V)
  analogReference(DEFAULT);
  
  // Optional: set the resolution to 10 bits (default on most Arduino boards)
  // analogReadResolution(10);

  // Initialize I2C
  Wire.begin();
}

void loop() {
  // Read the analog value (0-1023 for 10-bit ADC)
  int sensorValue = analogRead(voltagePin);
  
  // Convert the analog reading to voltage
  float voltage = (sensorValue * referenceVoltage) / 1023.0;
  
  // Apply voltage divider ratio if needed
  voltage *= voltageDividerRatio;
  
  // Display the voltage on the LCD
  lcd.setCursor(0, 0);
  lcd.print("Voltage: ");
  lcd.print(voltage, 2); // Display with 2 decimal places
  lcd.print(" V");
  
  // Clear the second line and show raw value (optional)
  lcd.setCursor(0, 1);
  lcd.print("Raw: ");
  lcd.print(sensorValue);
  lcd.print("    "); // Clear any remaining characters
  
  // Wait a bit before the next reading
  delay(500);
}