#include <LiquidCrystal.h>
const int RS = 12;
const int EN = 11;
const int D4 = 10;
const int D5 = 8;
const int D6 = 7;
const int D7 = 6;
LiquidCrystal lcd(RS, EN, D4, D5, D6, D7);
bool isPlaying = 0;       /* 0: Stop; 1: Play             */
bool countDirection = 0;  /* 0: Count Down; 1: Count Up   */
float countValue = 0.0;

void setup() {
  lcd.begin(16, 2);

  if (!isPlaying) {
    lcd.print("STOP");
  } else {
    if (countDirection) {
      lcd.print("COUNT_UP");
    } else {
      lcd.print("COUNT_DOWN");
    }
    
  }
  
  // Set up Timer1
  noInterrupts();	// Disable all interrupts
  TCCR1A = 0; 	// Reset TCCR1A register
  TCCR1B = 0; 	// Reset TCCR1B register
  // Set the prescaler to 1024 
  TCCR1B |= 0x05; 
  // Set the compare match value for 1s
  OCR1A = 15625; 	//（15625 ≒ 1s / (1 / (16MHz / 1024)))
  // Set the CTC mode
  TCCR1B |= (1 << WGM12); 
  // Enable Timer1 compare match A interrupt
  TIMSK1 |= (1 << OCIE1A);
  interrupts();    // Enable all interrupts
}

void loop() {
  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  // print the number of seconds since reset:
  lcd.print(countValue);
  lcd.print("s");
}

// Timer1 compare match A interrupt service routine
ISR(TIMER1_COMPA_vect) {
  countValue = 0.1;
 // Your custom code here
 // This code will be executed every 100ms
}

/*
Exercise 3. Stop Watch

Learning Objective
•	Timer interrupt, state transition, LCD control

Task Overview
•	Create a stopwatch system that uses an Arduino UNO, four buttons, and an LCD to perform count-up, countdown, and stop state transitions.

Input Specifications:
1.	Push button 1 (pin 5): Count up (enabled only when stopped)
2.	Push button 2 (pin 4): Countdown (enabled only while stopped)
3.	Push button 3 (pin 3): stop/count reset (Accepted at any time. Count reset enabled only while stopped)
4.	Push button 4 (pin 2): Reserve for next exercise
 
Output Specifications:
1.	LCD (Pins 12, 11, 10, 8, 7, 6): the first line shows the current state, the second line shows the count value (Seconds, up to one decimal place)

Required Features:
1.	When the power is turned ON, the following states and values are set.
a.	Status: STOP
b.	Count: 0.0 s
2.	The first line of the LCD always displays the current status (STOP/COUNT_UP/COUNT_DOWN), and the second line always displays the count value (**.* s).

Sample
C	O	U	N	T	_	D	O	W	N						
0	9	.	5	s											

3.	When push button 1 is pressed, count up is started. When the count reaches 20 seconds, the count stops (STOP).
4.	When the push button 2 is pressed, the countdown is started. When the count value reaches 0 seconds, the count stops (STOP).
5.	When the push button 3 is pressed during count up or count down, the count stops (STOP).
6.	When the push button 3 is pressed while the count is stopped, the count is reset.

Restrictions: 
•	The following libraries shall be prohibited:
・	PinMode
・	DigitalRead
・	DigitalWrite
・	millis()
・	micros()
(Use port manipulations.)

Reference Applications:

•	HelloWorld (under File->Examples->LiquidCrystal in Arduino IDE)
•	Timer Interrupt Example
The processing to perform the interrupt accurately every 1 second is described below. You can also change the interrupt cycle by reviewing each setting.

void setup() {
   // Set up Timer1
   noInterrupts();	// Disable all interrupts
   TCCR1A = 0; 	// Reset TCCR1A register
   TCCR1B = 0; 	// Reset TCCR1B register
   // Set the prescaler to 1024 
   TCCR1B |= 0x05; 
   // Set the compare match value for 1s
   OCR1A = 15625; 	//（15625 ≒ 1s / (1 / (16MHz / 1024)))
   // Set the CTC mode
   TCCR1B |= (1 << WGM12); 
   // Enable Timer1 compare match A interrupt
   TIMSK1 |= (1 << OCIE1A);
   interrupts();    // Enable all interrupts
}

// Timer1 compare match A interrupt service routine
ISR(TIMER1_COMPA_vect) {
 // Your custom code here
 // This code will be executed every 100ms
}

*/