// https://www.hackster.io/moty/frequency-counter-92ec57

/*
   LCD Counter
   Created: 12/08/2017 23:34:47
    Author: moty22.co.uk
*/

#include <LiquidCrystal.h>

byte overF = 0;
unsigned long freq;
double period;

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, A2, A3, A4, A5);

// the setup function runs once when you press reset or power the board
void setup() {

  lcd.begin(16, 2);   // set up the LCD's number of columns and rows:

  //1 Hz timer
  OCR0A = 249;
  TCCR0A = _BV(WGM00) | _BV(WGM01) | _BV(COM0A0); //
  TCCR0B = _BV(WGM02) | _BV(CS02) | _BV(CS01);  //  PWM mode, input T0 pin D4
  pinMode(6, OUTPUT);

  //250 Hz - timer2
  OCR2A = 249;
  OCR2B = 125;
  TCCR2A = _BV(COM2B1) | _BV(COM2B0) | _BV(WGM21) | _BV(WGM20);  //output B in phase, fast PWM mode
  TCCR2B = _BV(WGM22) | _BV(CS22) | _BV(CS21); // set prescaler to 256 and start the timer
  pinMode(3, OUTPUT);

  //  counter input T1 pin D5
  OCR1A = 32767;   //32768 counts
  TCCR1A = _BV(WGM10) | _BV(WGM11) | _BV(COM1A0); //
  TCCR1B = _BV(WGM12) | _BV(WGM13) | _BV(CS12) | _BV(CS11); //input pin D5
  pinMode(9, OUTPUT);

  lcd.setCursor(7, 0); // top middle
  lcd.print("hi");

}


// the loop function runs over and over again forever
void loop() {

  //wait for high
  while (digitalRead(6)) {}
  while (!digitalRead(6)) {}
  //start the count
  TIFR1 = _BV(OCF1A);    //reset int
  OCR1A = 32767;
  //OCR1A = 32755;
  TCNT1 = 0;
  overF = 0;
  while (digitalRead(6)) {
    if (TIFR1 & (1 << OCF1A)) {
      ++overF;  //overflow
      TIFR1 = _BV(OCF1A);
    }
  }
  //count end
  freq = (unsigned long)TCNT1 + ((unsigned long)overF * 32768);
  period = 1000000 / (double)freq;
  if (freq == 0) {
    period = 0;
  }

  lcd.clear();
  lcd.setCursor(3, 0); // top line
  lcd.print(freq, DEC);
  lcd.setCursor(11, 0);
  lcd.print("Hz");
  lcd.setCursor(3, 1);
  lcd.print(period, DEC);
  lcd.setCursor(10, 1);
  lcd.print(" uS   ");
}