#include <TimerOne.h>

void setup(void)
{
  pinMode(7, INPUT);
  Timer1.initialize(100);//1000000=1s
  Timer1.attachInterrupt(blinkLED);
  Serial.begin(9600);
}


int ledState = LOW,T=0,state0=0,state1=0;
volatile unsigned long blinkCount = 0;  variables

void blinkLED(void)
{
  T++;
}

void loop(void)
{
  state0=state1;
  state1=digitalRead(7);
  if(state0!=state1)
  {
    //Serial.print("state1=");
    //Serial.print(state1);
    //Serial.print("  T=");
    Serial.println(T);
    T=0;
  }
}