#define Channel_A     9
#define Channel_B     10
uint32_t number = 0;
volatile byte tmrCount = 0;
bool Enc_Run = false;
bool DIR;


void setup() 
{
  pinMode(Channel_A, OUTPUT);
  pinMode(Channel_B, OUTPUT);
  Serial.begin(9600);//enable serial monitor
  Serial.println("Interrupt timer1 calculator");
  Serial.println("--------------------");
}

ISR(TIMER1_COMPA_vect){
   //interrupt commands for TIMER 1 here
  switch (tmrCount & 3) {
  case 0:
    digitalWrite(Channel_A,HIGH);
    break;
  case 1:
    digitalWrite(Channel_B,HIGH);
    break;
  case 2:
    digitalWrite(Channel_A,LOW);
    break;
  case 3:
    digitalWrite(Channel_B,LOW);
  }
  number++;
  if (!DIR) {
    tmrCount++;
  }
  else {
    tmrCount--;
  }
}

void loop() {
while (Serial.available() == 0) {}
  
  int value = Serial.parseInt();
  float Freq;
  int Puls10Mtr=6522;
  float CompareReg;

  if(value > 0)
  {
    cli(); // stop interrupts
    TCCR1A = 0; // set entire TCCR1A register to 0
    TCCR1B = 0; // same for TCCR1B
    TCNT1  = 0; // initialize counter value to 0
    Freq=value;
    Serial.print("Fequency: ");
    Serial.print(Freq,5);
    Serial.println(" Hz");
    CompareReg=(16000000/(1*Freq))-1;
    if (CompareReg<65536){
      Serial.println("CS12 - CS10 = 001 : divide by 1");
      // Set CS12, CS11 and CS10 bits for 1 prescaler
      TCCR1B |= (0 << CS12) | (0 << CS11) | (1 << CS10);
      goto Found;
    }
    CompareReg=(16000000/(8*Freq))-1;
    if (CompareReg<65536){
      Serial.println("CS12 - CS10 = 010 : divide by 8");
      // Set CS12, CS11 and CS10 bits for 8 prescaler
      TCCR1B |= (0 << CS12) | (1 << CS11) | (0 << CS10);
      goto Found;
    }
    CompareReg=(16000000/(64*Freq))-1;
    if (CompareReg<65536){
      Serial.println("CS12 - CS10 = 011 : divide by 64");
      // Set CS12, CS11 and CS10 bits for 8 prescaler
      TCCR1B |= (0 << CS12) | (1 << CS11) | (1 << CS10);
      goto Found;
    }
    CompareReg=(16000000/(256*Freq))-1;
    if (CompareReg<65536){
      Serial.println("CS12 - CS10 = 100 : divide by 256");
      // Set CS12, CS11 and CS10 bits for 256 prescaler
      TCCR1B |= (1 << CS12) | (0 << CS11) | (0 << CS10);
      goto Found;
    }    CompareReg=(16000000/(1024*Freq))-1;
    if (CompareReg<65536){
      Serial.println("CS12 - CS10 = 101 : divide by 1024");
      // Set CS12, CS11 and CS10 bits for 1024 prescaler
      TCCR1B |= (1 << CS12) | (0 << CS11) | (1 << CS10);
      goto Found;
    }  
    Found:
    Serial.print("compare match register: ");
    Serial.println(word(CompareReg));

    DIR = false;
    // set compare match register
    OCR1A = word(CompareReg);
    // turn on CTC mode
    TCCR1B |= (1 << WGM12);
    // enable timer compare interrupt
    TIMSK1 |= (1 << OCIE1A);
    sei(); // allow interrupts
  }
}