DimmerAtmega

//#include <TimerOne.h>   //https://github.com/PaulStoffregen/TimerOne         [Attiny support]
#include<Timer1.h>        //https://github.com/carlosrafaelgn/ArduinoTimer/tree/master/Timer1


#include "PinChangeInterrupt.h"

#define MotorPin 4       // Triac Pin  [Physical Pin 3]
#define ZCD_Pin 1        // Zero Cross [Physical Pin 6]
//----------------------------------------------------------------------------------------------//
// Motor Speed Control
int fanval[5] = {90, 50, 20};         // Fan different Speed
int timeval;
bool interruptState = false;
boolean  fan;
byte speedCounter = 0;
volatile boolean fanON = 0;
bool machineState = false;
//----------------------------------------------------------------------------------------------//

char mode;

void setup() {
  Serial.begin(9600);
  pinMode(ZCD_Pin, INPUT);
  pinMode(MotorPin, OUTPUT);
  fan = false;
  attachPCINT(digitalPinToPCINT(ZCD_Pin), dimmer, FALLING);
//  attachInterrupt(0, dimmer, FALLING);
}

void dimmer()
{
  long int dimval;
  dimval = timeval * 75;
  if (fanON)
    startTimer1(dimval);
  //    Timer1.initialize(dimval);
}

ISR(timer1Event)
{
  //  Timer1.stop();
  pauseTimer1();
  digitalWrite(MotorPin, HIGH);
  delayMicroseconds(100);
  digitalWrite(MotorPin, LOW);
}
void loop() {

  if (Serial.available() > 0) {

    mode = Serial.read();
    //////////////////////////////////////////////////////////////////// OFF ////////////////////////////////////////////////////////////////////
    if (mode == '0')
    {
      Serial.println("OFF");
      if (machineState == true) {                 // Turn OFF only if it's ON
        fanON = 0;
        interruptState = false;
        machineState = false;
      }
    }
    //////////////////////////////////////////////////////////////////// LOW ////////////////////////////////////////////////////////////////////
    if (mode == '1')
    {
      Serial.println("LOW");
      if (machineState == false) {                        // Turn ON only if it's OFF

        speedCounter = 3;
        timeval = fanval[0];
        if (interruptState == false) {
          fanON = 1;
          interruptState = true;
        }
        machineState = true;
      }
    }
    //////////////////////////////////////////////////////////////////// MED ////////////////////////////////////////////////////////////////////
    if (mode == '2')
    {
      Serial.println("MED");
      timeval = fanval[1];
      if (interruptState == false) {
        fanON = 1;
        interruptState = true;
      }
    }
    //////////////////////////////////////////////////////////////////// HIGH ////////////////////////////////////////////////////////////////////
    if (mode == '3')
    {
      Serial.println("HIGH");
      timeval = fanval[2];
      if (interruptState == false) {
        fanON = 1;
        interruptState = true;
      }
    }
  }
}