Arduino encoder z Unity

#define btn 3
#define pinA 4 //clk
#define pinB 5 // dt

int counter = 0; 
int pos;
int lastPos;  

void setup() { 
   pinMode (pinA,INPUT);
   pinMode (pinB,INPUT);
   pinMode (btn,INPUT);
   Serial.begin (9600);
   lastPos = digitalRead(pinA);   
} 

void loop() { 
  //button func
  if(digitalRead(btn)==0)
  {
    counter=0;
    Serial.println(counter);
  }

  pos = digitalRead(pinA);
  if(pos == lastPos) return;

  if (digitalRead(pinB) == pos) { 
    counter ++;
  }else {
    counter --;
  }
  Serial.println(counter);
  lastPos = pos; 
  delay(20);
}

using UnityEngine;
using System.IO.Ports;
using System;

public class ArduinoConnection : MonoBehaviour
{
    SerialPort portNo = new SerialPort("COM3", 9600);

    public int Counter { get; private set; }

    void Start()
    {
        portNo.Open();
        portNo.ReadTimeout = 5000;
    }

    private void Update()
    {
        ReadEncoder();
    }

    
    void ReadEncoder()
    {
        if (portNo.IsOpen)
        {
            if (portNo.BytesToRead > 0)
            {
                string recData = portNo.ReadLine();
                if (Int32.TryParse(recData, out int x))
                {
                    Counter = x;
                }
                Debug.Log(Counter);
            }
        }
    }
}