从Java读取Arduino太慢了

Question

我正在尝试编写一个简单的Java程序，在一些物理传感器上的用户的刺激下，显示输入到Arduino板的模拟输入。

如果我使用Arduino程序本身并查看串行监视器，我会看到基于用户输入的模拟读数立即更新。但是，当从我的Java程序读取输入时，在物理刺激和显示值之间有很大的延迟(5-6秒)。

上传到Arduino的代码非常简单，只需通过一堆模拟端口循环并打印数据：

void setup() {
  Serial.begin(9600);
  pinMode(30, OUTPUT);
}

void loop() 
  digitalWrite(30, HIGH);

  for (int i = 0; i < 10; i++) {
    int sensorValue = analogRead(i);
    Serial.print(String(i) + ":");
    Serial.println(sensorValue);
  }
}

我使用的Java代码几乎全部复制自here提供的示例，除了我更新了端口名称以适用于我的系统(MacOSX10.10.3)之外。

下面是Java代码：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier; 
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent; 
import gnu.io.SerialPortEventListener; 
import java.util.Enumeration;


public class SerialTest implements SerialPortEventListener {

    SerialPort serialPort;

    /** The port we're normally going to use. */
    private static final String PORT_NAMES[] = { 
            "/dev/cu.usbmodem1411",
            "/dev/cu.usbmodem1451",
    };

    /**
    * A BufferedReader which will be fed by a InputStreamReader 
    * converting the bytes into characters 
    * making the displayed results codepage independent
    */
    private BufferedReader input;

    /** The output stream to the port */
    private OutputStream output;

    /** Milliseconds to block while waiting for port open */
    private static final int TIME_OUT = 2000;

    /** Default bits per second for COM port. */
    private static final int DATA_RATE = 9600;

    public void initialize() {
        CommPortIdentifier portId = null;
        Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();

        //First, Find an instance of serial port as set in PORT_NAMES.
        while (portEnum.hasMoreElements()) {
            CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
            for (String portName : PORT_NAMES) {
                if (currPortId.getName().equals(portName)) {
                    portId = currPortId;
                    break;
                }
            }
        }
        if (portId == null) {
            System.out.println("Could not find COM port.");
            return;
        }

        try {
            // open serial port, and use class name for the appName.
            serialPort = (SerialPort) portId.open(this.getClass().getName(),
                    TIME_OUT);

            // set port parameters
            serialPort.setSerialPortParams(DATA_RATE,
                    SerialPort.DATABITS_8,
                    SerialPort.STOPBITS_1,
                    SerialPort.PARITY_NONE);

            // open the streams
            input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
            output = serialPort.getOutputStream();

            // add event listeners
            serialPort.addEventListener(this);
            serialPort.notifyOnDataAvailable(true);
        } catch (Exception e) {
            System.err.println(e.toString());
        }
    }

    /**
     * This should be called when you stop using the port.
     * This will prevent port locking on platforms like Linux.
     */
    public synchronized void close() {
        if (serialPort != null) {
            serialPort.removeEventListener();
            serialPort.close();
        }
    }

    /**
     * Handle an event on the serial port. Read the data and print it.
     */
    public synchronized void serialEvent(SerialPortEvent oEvent) {
        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                String inputLine=input.readLine();
                System.out.println(inputLine);
            } catch (Exception e) {
                System.err.println(e.toString());
            }
        }
        // Ignore all the other eventTypes, but you should consider the other ones.
    }

    public static void main(String[] args) throws Exception {
        SerialTest main = new SerialTest();
        main.initialize();
        Thread t=new Thread() {
            public void run() {
                //the following line will keep this app alive for 1000 seconds,
                //waiting for events to occur and responding to them (printing incoming messages to console).
                try {Thread.sleep(1000000);} catch (InterruptedException ie) {}
            }
        };
        t.start();
        System.out.println("Started");
    }
}

该程序所做的全部工作就是打印出Arduino串行监视器的值，但是通过Java所花费的时间(5-6秒)要比Arduino程序本身所花费的时间长得多。

1)为什么会发生这种情况？

2)如何修复？

Answer 1

对我有效的答案是在我的Arduino代码中添加一个delay方法。显然，Java已经被输入的速度压垮了。

当然，Java仍然可以以足够快的速度读取，这有任何实际的区别。