在Java中读取串口 [英] Reading serial port in Java

问题描述

我是Java的初学者。我正在通过串口从设备读取数据。我每分钟都会获得一次数据，但是在数据正确显示之后，第一次读数会变为一半。

I'm beginner in Java. I'm reading data from device through serial port. I'm getting data for every one minute, but first reading is coming half, after that data is coming correctly.

我得到的输出是：

6050.003120815340006050.003120815350006050.0

6050.003120815340006050.003120815350006050.0

正确的输出应该是这样的：

Correct output should be like this:

03120815340006050.003120815350006050.0

03120815340006050.003120815350006050.0

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我的代码是：

My code is:

import java.io.*;
import java.util.*; //import gnu.io.*;
import javax.comm.*;

public class SimpleRead implements Runnable, SerialPortEventListener {
    static CommPortIdentifier portId;
    static Enumeration portList;

InputStream inputStream;
SerialPort serialPort;
Thread readThread;
byte[] readBuffer;

public static void main(String[] args) {
    portList = CommPortIdentifier.getPortIdentifiers();
    System.out.println("portList... " + portList);
    while (portList.hasMoreElements()) {
        portId = (CommPortIdentifier) portList.nextElement();
        if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
            System.out.println("port identified is Serial.. "
                    + portId.getPortType());
            if (portId.getName().equals("COM2")) {
                System.out.println("port identified is COM2.. "
                        + portId.getName());
                // if (portId.getName().equals("/dev/term/a")) {
                SimpleRead reader = new SimpleRead();
            } else {
                System.out.println("unable to open port");
            }
        }
    }
}

public SimpleRead() {
    try {
        System.out.println("In SimpleRead() contructor");
        serialPort = (SerialPort) portId.open("SimpleReadApp1111",500);
        System.out.println(" Serial Port.. " + serialPort);
    } catch (PortInUseException e) {
        System.out.println("Port in use Exception");
    }
    try {
        inputStream = serialPort.getInputStream();
        System.out.println(" Input Stream... " + inputStream);
    } catch (IOException e) {
        System.out.println("IO Exception");
    }
    try {
        serialPort.addEventListener(this);

    } catch (TooManyListenersException e) {
        System.out.println("Tooo many Listener exception");
    }
    serialPort.notifyOnDataAvailable(true);
    try {

        serialPort.setSerialPortParams(9600, SerialPort.DATABITS_8,
                SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);

        // no handshaking or other flow control
        serialPort.setFlowControlMode(SerialPort.FLOWCONTROL_NONE);

        // timer on any read of the serial port
        serialPort.enableReceiveTimeout(500);

        System.out.println("................");

    } catch (UnsupportedCommOperationException e) {
        System.out.println("UnSupported comm operation");
    }
    readThread = new Thread(this);
    readThread.start();
}

public void run() {
    try {
        System.out.println("In run() function ");
        Thread.sleep(500);
        // System.out.println();
    } catch (InterruptedException e) {
        System.out.println("Interrupted Exception in run() method");
    }
}

public void serialEvent(SerialPortEvent event) {

    // System.out.println("In Serial Event function().. " + event +
    // event.getEventType());
    switch (event.getEventType()) {
    /*
     * case SerialPortEvent.BI: case SerialPortEvent.OE: case
     * SerialPortEvent.FE: case SerialPortEvent.PE: case SerialPortEvent.CD:
     * case SerialPortEvent.CTS: case SerialPortEvent.DSR: case
     * SerialPortEvent.RI: case SerialPortEvent.OUTPUT_BUFFER_EMPTY: break;
     */
    case SerialPortEvent.DATA_AVAILABLE:
        readBuffer = new byte[8];

        try {

            while (inputStream.available()>0) {

                int numBytes = inputStream.read(readBuffer);
            //   System.out.println("Number of bytes read " + numBytes);
            }

            System.out.print(new String(readBuffer));

        } catch (IOException e) {
            System.out.println("IO Exception in SerialEvent()");
        }
        break;
    }
    // System.out.println();
/*  String one = new String(readBuffer);
    char two = one.charAt(0);
    System.out.println("Character at three: " + two);*/
}

}

推荐答案

使用以下内容：

while (inputStream.available()>0) {
  int numBytes = inputStream.read(readBuffer);
  System.out.print(new String(readBuffer));
}

您正在从while循环中打印结果。但是循环中的代码可能会运行多次，因此数据块将丢失。

You are printing the result out of the while loop. However the code inside the loop may run more than once, so chunk of data will be lost.

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