arduino 傳string型別變數至unity，unity利用serialport的ReadLine()方法讀出來是String型態。如果我想把這個String型態變數轉換為float(我是用float.parse(string變數))結果印不出來。這應該要如何解決呢?謝謝~

//unity程式碼
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.IO.Ports;
public class NewBehaviourScript1 : MonoBehaviour {

SerialPort sp=new SerialPort("COM4",9600);
//float num=0;
// Use this for initialization
void Start () {
	sp.Open ();
	sp.ReadTimeout = 10000;
}
// Update is called once per frame
void Update () {
	if (sp.IsOpen) {
		try{
			float data= float.Parse(sp.ReadLine());
			print(data);
			this.gameObject.transorm.Rotate(new Vector3(0f,0f,data));
		}
		catch(System.Exception){
		}
	}
}	

}
//arduino程式碼
const int outputA=6;
const int outputB=7;
float counter=0;
int aState;
int aLastState;
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);

pinMode(outputA,INPUT);
pinMode(outputB,INPUT);

aLastState=digitalRead(outputA);
}
void loop() {
// put your main code here, to run repeatedly:
aState=digitalRead(outputA);
if(aState!=aLastState){
if(digitalRead(outputB)!=aState){
counter--;
}
else{
counter++;
}
Serial.print("Position: ");
Serial.println(String(counter));
}
aLastState=aState;
}