//////////////////////////////////////////////////////
//ATtiny85 Period Time & Frequency counting via ISR;
// Time counting more than 255
// Mokhtar Zerdali 2022.
#include<avr/io.h>
#include<util/delay.h>
#include <TinyDebug.h>

#define F_CPU 8000000UL
#define INT_PIN PB2 // INT0 -> PB2 external interrupt pin

volatile unsigned long Overflow ; // value >256, and volatile between void programs
volatile unsigned long Count;
volatile unsigned long Time;
volatile unsigned long Start_Time;
volatile unsigned long Finish_Time;
volatile unsigned long Elapsed_Time;
volatile  float Frequency;
volatile  int PRB;// pulse rate beat

volatile byte  i;

void counter_setup()
{
  //Debug.begin( 9600 );    // for tiny_debug_serial
  Debug.begin();
  //Debug.println(F("Hello, clock is running"));
  DDRB = (1 << PB1) | (1 << PB0) | (1 << PB3) | (1 << PB4);

  TCCR0A = 0X00; //TCCR0A to low for normal port operation and mode 0.
  TCCR0B = 0X00; //WGM02=0
  TCCR0B |= (1 << CS00); //No prescaling clk
  TCNT0 = 0; //initializing the counter to 0
  // Overflow >255 interrupts
  TIMSK = bit (TOIE0); //|= (1 << TOIE0); //enabling overflow interrupts of  timer0
  Overflow = 0;
  //Externall interrupts
  GIMSK |= (1 << INT0); // enable external interrupt

  // Mode sense of MCUCR Register to choose the adequate sense
  /////////////////////////////////////
 // MCUCR &= ~(bit(ISC01) | bit(ISC00));    //1/ INT0 on low level
// The low level of INT0 generates an interrupt request
  //MCUCR = //(1 << ISC00); //2/ Any Logical mode sense
 MCUCR = (1 << ISC01); //3/ FALLING mode sense
  //MCUCR = bit(ISC01) | bit(ISC00); //4// RISING mode sense
  sei(); //global interruption
}
///////////////////////////////
ISR (TIMER0_OVF_vect) //Interrupt vector for Timer0 >>>> Counter0
{
  Overflow++; // count number of overflow
} // End of TIMER0_OVF_vect
//////////////////////////////
ISR(INT0_vect) // Interrupter vector for external inerruption
{
  i = digitalRead(PB2);
  digitalWrite(PB1, i);

  Count = TCNT0 + (Overflow << 8); //n° overflow*256
  Time = 0.000125 * Count; // 8MHz ; clk : 125 ns.
  Start_Time = Time;

  //Debug.println("Start_Time:");
  //Debug.print(Start_Time);
  //Debug.println("ms");
  //Debug.println("###:");

  //Debug.println("Elapsed_Time:");
  //Debug.print(Elapsed_Time);
  //Debug.println("ms");
  //Debug.println("###:");

  Debug.println("Frequency:");
  Debug.print(Frequency);
  Debug.println("Hz");
  Debug.println("###:");

Debug.println("Pulse rate beat:");
  Debug.print(PRB);// heart
  Debug.println("/min");
  Debug.println("###:");
}
///////////////////////////////////
int main()
{
  counter_setup();
  while (1)
  {
    Count = TCNT0 + (Overflow << 8); //n° overflow*256
    Time = 0.000125 * Count; // 8MHz ; clk : 125 ns.

    Finish_Time = Time;
    Elapsed_Time = Finish_Time - Start_Time;
    Frequency = 1000 / float(Elapsed_Time); // on Hz
    PRB = 60* Frequency; //pulse rate beat
    //if (Start_Time > 1500)
    {
      PORTB = bit(PB0);

    }
  }
}