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

LiquidCrystal_I2C lcd(0x27, 16, 2);

int analogInput = A1;
float vout = 0.0;
float vin = 0.0;
float R1 = 100000.0;
float R2 = 10000.0;
int value = 0;

void setup() {
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("DC VOLTMETER");
}

void loop() {
  value = analogRead(analogInput);
  vout = (value * 5.0) / 1024.0;
  vin = vout / (R2 / (R1 + R2));

  if (vin < 0.01) vin = 0.0;

  Serial.print("Vout (A1 Pin): ");
  Serial.print(vout, 2);
  Serial.print("V | Vin (Calculated): ");
  Serial.print(vin, 2);
  Serial.println("V");

  lcd.setCursor(0, 1);
  lcd.print("INPUT V= ");
  lcd.print(vin, 2);
  lcd.print("  ");

  delay(500);
}