Fever thermometer on an Arduino Uno

// Fever thermometer: an MLX90614 infrared thermometer, a 16x2 I2C LCD and a
// piezo.
//
//   SDA, SCL  the MLX90614 (0x5A) and the LCD backpack (0x27), one bus
//   pin 8     the piezo; its other leg to ground
//
// The MLX90614 reads the temperature of what it is pointed at without
// touching it, here a forehead a couple of centimeters away, and its own
// (the ambient). Twice a second the LCD shows both; over 38.0 C the first
// line says FEVER and the piezo beeps.
//
// readObjectTempC() returns a float; the sketch works in tenths of a degree
// so the comparison and the display are whole numbers.

#include <Wire.h>
#include <Adafruit_MLX90614.h>
#include <LiquidCrystal_I2C.h>

const int PIEZO = 8;
const int FEVER_TENTHS = 380;

Adafruit_MLX90614 mlx = Adafruit_MLX90614();
LiquidCrystal_I2C lcd(0x27, 16, 2);

void printTenths(int tenths) {
  if (tenths < 0) {
    lcd.print('-');
    tenths = -tenths;
  }
  lcd.print(tenths / 10);
  lcd.print('.');
  lcd.print(tenths % 10);
}

void setup() {
  Serial.begin(115200);
  Serial.println("Mokxi Arduino Uno: fever thermometer");
  lcd.init();
  lcd.backlight();
  if (!mlx.begin()) {
    lcd.print("No MLX90614");
    Serial.println("no MLX90614: check SDA, SCL and power");
    while (1) delay(10);
  }
}

void loop() {
  int object = (int)(mlx.readObjectTempC() * 10.0 + 0.5);
  int ambient = (int)(mlx.readAmbientTempC() * 10.0 + 0.5);
  bool fever = object > FEVER_TENTHS;

  lcd.setCursor(0, 0);
  lcd.print(fever ? "FEVER " : "Temp  ");
  printTenths(object);
  lcd.print(" C   ");
  lcd.setCursor(0, 1);
  lcd.print("Room  ");
  printTenths(ambient);
  lcd.print(" C   ");

  Serial.print("forehead ");
  Serial.print(object / 10);
  Serial.print('.');
  Serial.print(object % 10);
  Serial.print(" C");
  Serial.println(fever ? "  FEVER" : "");
  if (fever) tone(PIEZO, 2000, 150);
  delay(500);
}