处理 - > Arduino - >通过端口进行Unity通信

Question

What I try to do: Processing 3 is receiving a sort of QR code via my webcam --> it reads the value and sends it to my Arduino, Arduino successfully receives it and can now do stuff with it. Now I want to add another communication channel, Unity. I want the Arduino to send the value from the Processing to Unity. It is easy to communicate between Arduino and Unity, but I need Processing for the webcam value.

The problem: Both Processing 3 and Unity make use of the same port (COM4, 9600). This will cause an IO exception in Unity saying "Access Denied" followed by errors of the Serial port isn't open.

Processing 3 code

...
 //Open port
  String portName = Serial.list()[0];
  myPort = new Serial(this, portName, 9600);
  myPort.write(1);
...

Arduino code

void setup() {
  // put your setup code here, to run once:
   ...
   Serial.begin(9600); // Start serial communication at 9600 bps
   ...
}

void loop() {
  if (Serial.available()) { // If data is available to read,
    val = Serial.read(); // read it and store it in val
  }
  //val contains now the data that was sent from Processing 3
  //Send this data to Unity:
  Serial.flush();
  Serial.println(val);
}

Unity code

...
SerialPort stream = new SerialPort ("COM4", 9600); //We obviously can't open this port since its already in use by Processing 3. How to fix this?
...
// Use this for initialization
    void Start () {
        stream.Open(); //Throws IO exception: Access Denied error
    }
    // Update is called once per frame
    void Update () {
        string value = stream.ReadLine();
        val = int.Parse(value);
        if (val == 1) {
            //Links van arduino
            goLeft();
        }else if (val == 2) {
            //Rechts van arduino
            goRight();
        }

    }

We obviously can't open the port in Unity since its already in use by Processing 3. How to fix this? Communication stream:

Processing 3 --> Arduino --> Unity

Eventually Unity needs to know whether you have to go Left or Right based on the QR code input on the webcam.

Answer 1

You can't use the same serial port in two concurrent applications (why do you want to use an Arduino at all?) A solution is to establish alink between applications. A network connection, using a 127.0.0.1 loopback connection, is a tried and tested way of creating that link.

As far as protocols go, you have endless options, my personal preference is to use OSC - both processing (via OSCP5) and Unity (various plugins, including my own I should really make public at some point) have decent support for messaging, but you can use many other types of links (ie. websockets)

Answer 2

For the people who would like to know how to solve this problem. You can't. We have to think in another way. Options were:

1. Close port while done processing and then open port in Unity (was not practical since we need a constant stream of instructions)
2. Leave out the Arduino and communicate between Processing and Unity (was not practical either since we need the Arduino in this case for blinkers)
3. Find another communication form between the Arduino/Processing and Unity without any ports. (Thanks to @kaj)

I've implemented the last option

• Output Processing results to a "data.txt" file
• Unity opens this file in C# with ReadAccess FileStream and reads the output and uses this

In this way we can still use the Arduino and Unity directly reads output from the Processing without a middleman.