#include <Wire.h>
#include <TM1637TinyDisplay.h> 
 
int rpm;  // ex float

float value=0;
float rev=0;

int oldtime=0;        
int time;

#define CLK 5
#define DIO 3

TM1637TinyDisplay display(CLK, DIO);


void count() {
  rev++;
}

void setup()
{
  Serial.begin(9600);

  pinMode(2, INPUT);
    attachInterrupt(digitalPinToInterrupt(2), count, RISING); //RISING or //CHANGE
  delay(100); // ?
  
  display.begin();
  
}
void loop()
{
delay(100);// 2 second delay
detachInterrupt(digitalPinToInterrupt(2));           //detaches  the interrupt while calculating
time=millis()-oldtime;        //finds the time  
rpm=(rev/time)*600;         //calculates rpm
oldtime=millis();             //saves  the current time
rev=0;

if(rpm>1){
  Serial.println(rpm); 
  }
  display.showNumber(rpm);
   // display.showNumber(rpm, true, 4, 0); 

attachInterrupt(digitalPinToInterrupt(2), count, RISING);
  
 }