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

LiquidCrystal_I2C lcd(0x27, 16, 2);
void setup() {
  // put your setup code here, to run once:
  Wire.setSDA(8); Wire.setSCL(9);
  Wire.begin();

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Voltmeter");
  lcd.setCursor(0, 1);
  lcd.print("E = ");

  analogReadResolution(12);
  analogWriteResolution(12);
  analogWriteFreq(500);

}

void int_lcd(int row, int column, double num, int fp, String txt) {
  lcd.setCursor(column, row);
  lcd.print(num, fp);

  // clear error display
  if( num < 10) column = column + fp + 2;
  else if( (num >= 10) && (num < 100) ) column = column + fp + 3;
  else if( (num >= 100) && (num< 1000) ) column = column + fp + 4;
  else if( (num >= 1000) && (num< 10000) ) column = column + fp + 5;
  lcd.setCursor(column, row);
  lcd.print(txt + "        ");

}

void loop() {

  // int_lcd(1, 4, ((analogRead(A0) * 1000) / 4096), 2, "V");
  int_lcd(1, 4, map(analogRead(A0), 0, 4096, 0, 10000), 2, "V");
  delay(100);
  // put your main code here, to run repeatedly:
}