// |———————————————————————————————————————————————————————| 
// |  made by Arduino_uno_guy 11/13/2019                   |
// |   https://create.arduino.cc/projecthub/arduino_uno_guy|
// |———————————————————————————————————————————————————————|


#include <LiquidCrystal_I2C.h>

//#include  Wire.h

#define led_pin 13

//initialize the liquid crystal library
//the first parameter is  the I2C address
//the second parameter is how many rows are on your screen
//the  third parameter is how many columns are on your screen
LiquidCrystal_I2C lcd(0x27,  16, 2);

void setup() {

   // 設定 A0 為輸入
   pinMode(A0, INPUT);

   pinMode(led_pin, OUTPUT);

  //initialize lcd screen
  lcd.init();
  // turn on the backlight
  lcd.backlight();
}
void loop() {
  //wait  for a second
  delay(1000);
  // tell the screen to write on the top row
  //lcd.setCursor(0,0);
  // tell the screen to write “hello, from” on the top  row
  //lcd.print("Hello, From");
  // tell the screen to write on the bottom  row
  lcd.setCursor(0,1);
  // tell the screen to write “Arduino_uno_guy”  on the bottom row
  // you can change whats in the quotes to be what you want  it to be!
  lcd.print("Arduino_uno_guy");

  printVolts();
  
}

void printVolts()
{
  int sensorValue = analogRead(A0); //read the A0 pin value
  float voltage = sensorValue * (5.00 / 1023.00) * 2; //convert the value to a true voltage.
  lcd.setCursor(0,0);
  lcd.print("voltage = ");
  lcd.print(voltage); //print the voltage to LCD
  lcd.print(" V");
  if (voltage < 6.50) //set the voltage considered low battery here
  {
    digitalWrite(led_pin, HIGH);
  }
}