Unity animation slows with serial port open

Question

I am creating a simple unity program where a serial data is sent from Arduino and processed in Unity using C#. Depending on the value received, two different animations are played.

Arduino Code:

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

void loop() {
  int val=random(0,1);
  if(val==1){
    Serial.flush();
    Serial.println(1);
  }
  else{
    Serial.flush();
    Serial.println(0);
    }
  }
  delay(500);
}

Unity C# code:

using System.Collections;
using System.Collections.Generic;
using System.Threading;
using System.IO.Ports;
using UnityEngine;

public class ard : MonoBehaviour
{
    private SerialPort data_stream = new SerialPort("COM3", 9600);
    public GameObject kid;

    // Start is called before the first frame update
    void Start()
    {
        data_stream.Open();
    }

    // Update is called once per frame
    void Update()
    {
        if (data_stream.IsOpen) { 
            string val=data_stream.ReadLine();
            if (val == "0") {
                kid.GetComponent<Animator>().Play("Standing Idle To Fight Idle");
            }
            else if(val == "1")
            {
                kid.GetComponent<Animator>().Play("Fast Run");
            }
        }

    }
}

Arduino sends the data and Unity receives it perfectly fine. The only model I use in the Unity scene is the boy model from Mixamo. The problem is that the animation is really slow and choppy even with my RTX3050. If I replace the serial code with an ordinary keyboard input, it animates flawlessly.

What do I need to change to make the animations smooth while taking serial data as input?

Answer 1

Try replacing your line

if (data_stream.IsOpen) {

with

if (data_stream.IsOpen && data_stream.BytesToRead > 0) {

Also for the sake of testing I would be tempted to change your Arduino code so that every second or two it flipped between sending a 1 and a zero, rather than randomly every 500ms.