Picses' sky

一个嵌入式系统通常需要通过串口与其主控系统进行全双工通讯，譬如一个流水线
控制系统需要不断的接受从主控系统发送来的查询和控制信息，并将执行结果或查
询结果发送回主控系统。本文介绍了一个简单的通过串口实现全双工通讯的Java类
库，该类库大大的简化了对串口进行操作的过程。

本类库主要包括：SerialBean.java (与其他应用程序的接口), SerialBuffer.java
(用来保存从串口所接收数据的缓冲区), ReadSerial.java (从串口读取数据的程序)。
另外本类库还提供了一个例程SerialExample.java 作为示范。在下面的内容中将逐
一对这几个部分进行详细介绍。

1. SerialBean

SerialBean是本类库与其他应用程序的接口。该类库中定义了SerialBean的构造方
法以及初始化串口，从串口读取数据，往串口写入数据以及关闭串口的函数。具体
介绍如下：

public SerialBean(int PortID)

本函数构造一个指向特定串口的SerialBean，该串口由参数PortID所指定。
PortID = 1 表示COM1，PortID = 2 表示COM2，由此类推。

public int Initialize()

本函数初始化所指定的串口并返回初始化结果。如果初始化成功返回1，否
则返回-1。初始化的结果是该串口被SerialBean独占性使用，其参数被设置
为9600, N, 8, 1。如果串口被成功初始化，则打开一个进程读取从串口传
入的数据并将其保存在缓冲区中。

public String ReadPort(int Length)

本函数从串口(缓冲区)中读取指定长度的一个字符串。参数Length指定所返
回字符串的长度。

public void WritePort(String Msg)

本函数向串口发送一个字符串。参数Msg是需要发送的字符串。

public void ClosePort()

本函数停止串口检测进程并关闭串口。

SerialBean的源代码如下：

package serial;

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

/**
*
* This bean provides some basic functions to implement full dulplex
* information exchange through the srial port.
*
*/

public class SerialBean
{

static String PortName;
CommPortIdentifier portId;
SerialPort serialPort;
static OutputStream out;
static InputStream in;

SerialBuffer SB;
ReadSerial RT;

/**
*
* Constructor
*
* @param PortID the ID of the serial to be used. 1 for COM1,
* 2 for COM2, etc.
*
*/

public SerialBean(int PortID)
{
PortName = "COM" + PortID;
}

/**
*
* This function initialize the serial port for communication. It starts a
* thread which consistently monitors the serial port. Any signal captured
* from the serial port is stored into a buffer area.
*
*/

public int Initialize()
{

int InitSuccess = 1;
int InitFail = -1;

try
{

portId = CommPortIdentifier.getPortIdentifier(PortName);

try
{
serialPort = (SerialPort)
portId.open("Serial_Communication", 2000);
} catch (PortInUseException e)
{
return InitFail;
}

//Use InputStream in to read from the serial port, and OutputStream
//out to write to the serial port.

try
{
in = serialPort.getInputStream();
out = serialPort.getOutputStream();
} catch (IOException e)
{
return InitFail;
}

//Initialize the communication parameters to 9600, 8, 1, none.

try
{
serialPort.setSerialPortParams(9600,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
} catch (UnsupportedCommOperationException e)
{
return InitFail;
}
} catch (NoSuchPortException e)
{
return InitFail;
}

// when successfully open the serial port, create a new serial buffer,
// then create a thread that consistently accepts incoming signals from
// the serial port. Incoming signals are stored in the serial buffer.

SB = new SerialBuffer();
RT = new ReadSerial(SB, in);
RT.start();

// return success information

return InitSuccess;
}

/**
*
* This function returns a string with a certain length from the incoming
* messages.
*
* @param Length The length of the string to be returned.
*
*/

public String ReadPort(int Length)
{
String Msg;
Msg = SB.GetMsg(Length);
return Msg;
}

/**
*
* This function sends a message through the serial port.
*
* @param Msg The string to be sent.
*
*/

public void WritePort(String Msg)
{
int c;
try
{
for (int i = 0; i < Msg.length(); i++)
out.write(Msg.charAt(i));
} catch (IOException e) {}
}

/**
*
* This function closes the serial port in use.
*
*/

public void ClosePort()
{
RT.stop();
serialPort.close();
}
}

2. SerialBuffer

SerialBuffer是本类库中所定义的串口缓冲区，它定义了往该缓冲区中写入数据和
从该缓冲区中读取数据所需要的函数。

public synchronized String GetMsg(int Length)

本函数从串口(缓冲区)中读取指定长度的一个字符串。参数Length指定所
返回字符串的长度。

public synchronized void PutChar(int c)

本函数望串口缓冲区中写入一个字符，参数c 是需要写入的字符。

在往缓冲区写入数据或者是从缓冲区读取数据的时候，必须保证数据的同
步，因此GetMsg和PutChar函数均被声明为synchronized并在具体实现中采
取措施实现的数据的同步。

SerialBuffer的源代码如下：

package serial;

/**
*
* This class implements the buffer area to store incoming data from the serial
* port.
*
*/

public class SerialBuffer
{
private String Content = "";
private String CurrentMsg, TempContent;
private boolean available = false;
private int LengthNeeded = 1;

/**
*
* This function returns a string with a certain length from the incoming
* messages.
*
* @param Length The length of the string to be returned.
*
*/

public synchronized String GetMsg(int Length)
{
LengthNeeded = Length;
notifyAll();

if (LengthNeeded > Content.length())
{
available = false;
while (available == false)
{
try
{
wait();
} catch (InterruptedException e) { }
}
}

CurrentMsg = Content.substring(0, LengthNeeded);
TempContent = Content.substring(LengthNeeded);
Content = TempContent;
LengthNeeded = 1;
notifyAll();
return CurrentMsg;
}

/**
*
* This function stores a character captured from the serial port to the
* buffer area.
*
* @param t The char value of the character to be stored.
*
*/

public synchronized void PutChar(int c)
{
Character d = new Character((char) c);
Content = Content.concat(d.toString());
if (LengthNeeded < Content.length())
{
available = true;
}
notifyAll();
}
}

3. ReadSerial

ReadSerial是一个进程，它不断的从指定的串口读取数据并将其存放到缓冲区中。

public ReadSerial(SerialBuffer SB, InputStream Port)

本函数构造一个ReadSerial进程，参数SB指定存放传入数据的缓冲区，参
数Port指定从串口所接收的数据流。

public void run()

ReadSerial进程的主函数，它不断的从指定的串口读取数据并将其存放到
缓冲区中。

ReadSerial的源代码如下：

package serial;

import java.io.*;

/**
*
* This class reads message from the specific serial port and save
* the message to the serial buffer.
*
*/

public class ReadSerial extends Thread
{
private SerialBuffer ComBuffer;
private InputStream ComPort;

/**
*
* Constructor
*
* @param SB The buffer to save the incoming messages.
* @param Port The InputStream from the specific serial port.
*
*/

public ReadSerial(SerialBuffer SB, InputStream Port)
{
ComBuffer = SB;
ComPort = Port;
}

public void run()
{
int c;
try
{
while (true)
{
c = ComPort.read();
ComBuffer.PutChar(c);
}
} catch (IOException e) {}
}
}

4. SerialExample

SerialExample是本类库所提供的一个例程。它所实现的功能是打开串口COM1，对
其进行初始化，从串口读取信息对其进行处理后将处理结果发送到串口。

import serial.*;
import java.io.*;

/**
*
* This is an example of how to use the SerialBean. It opens COM1 and reads
* six messages with different length form the serial port.
*
*/

class SerialExample
{
public static void main(String[] args)
{
//TO DO: Add your JAVA codes here

SerialBean SB = new SerialBean(1);
String Msg;

SB.Initialize();
for (int i = 5; i <= 10; i++)
{
Msg = SB.ReadPort(i);
SB.WritePort("Reply: " + Msg);
}
SB.ClosePort();
}
}

5. 编译与调试

本类库中使用了Java Communication API (javax.comm)。这是一个Java扩展类库，
并不包括在标准的Java SDK当中。如果你尚未安装这个扩展类库的话，你应该从Sun
公司的Java站点下载这个类库并将其安装在你的系统上。在所下载的包里面包括一个
安装说明，如果你没有正确安装这个类库及其运行环境的话，运行这个程序的时候你
会找不到串口。

正确安装Java Communication API并将上述程序编译通过以后，你可以按如下方法测
试这个程序。如果你只有一台机器，你可以利用一条RS-232电缆将COM1和COM2连接起
来，在COM1上运行SerialExample，在COM2上运行Windows提供的超级终端程序。如果
你有两台机器的话，你可以利用一条RS-232电缆将两台机器的COM1(或者是COM2)连接
起来，在一端运行例程，另外一端运行Windows提供的超级终端程序。如果有必要的
话，可以对SerialExample中所声明的串口进行相应改动。

本程序在Windows 2000 + Java SDK 1.3环境下编译通过并成功运行。

　　以下是用Java读取串口的程序。

这个简单的程序包括以下文件：

       IMU.java (主程序)
       ReadBuffer.java (从缓冲区读取一个消息)
       ReadSerial.java (读取串口数据并放入缓冲区)
       SerialBuffer.java (缓冲区)
       WriteSerial.java (不断的往串口送星号'*')

测试程序：

       SendCom.java (将一个数据文件往串口发送)
       SEND.TXT (供测试用的数据文件)

在这个通讯程序中使用了一个简单的协议，既不同的消息之间用星号'*'作为分隔。这个程序中的问题是ReadSerial进程和WriteSerial进程不能够同时启动，出错信息是不能够打开串口，因为同样一个串口不能够同时被打开两次(在ReadSerial中声明了FileReader和在WriteSerial中声明了FileWriter)。这样是不能够实现全双工通讯的。

/*
*
* IMU.java 1.0
* Main Program for Serial Communication
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu
*
*/

import java.io.*;

class IMU
{
       public static void main(String[] args)
       {
               //TO DO: Add your JAVA codes here

               File ComPort = new File("COM1");

       SerialBuffer SB = new SerialBuffer();
       ReadSerial r1 = new ReadSerial(SB, ComPort);
       ReadBuffer r2 = new ReadBuffer(SB);
       WriteSerial r3 = new WriteSerial(ComPort);

       r1.start();
       r2.start();
       r3.start();
   }
}

/*
*
* ReadBuffer.java 1.0
* Program to Read the Serial Buffer
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu

*
*/

import java.io.*;

public class ReadBuffer extends Thread
{
   private SerialBuffer ComBuffer;

   public ReadBuffer(SerialBuffer SB)
   {
       ComBuffer = SB;
   }

   public void run()
   {
               String Msg;

       while (true)
       {
               Msg = ComBuffer.GetMsg();
               System.out.println(Msg);
       }

   }
}

/*
*
* ReadSerial.java 1.0
* Program to read characters from the serial port and put it
* to the buffer
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
*       qjiang@tsinghua.edu
*
*/

import java.io.*;

public class ReadSerial extends Thread
{
   private SerialBuffer ComBuffer;
   private File ComPort;

   public ReadSerial(SerialBuffer SB, File Port)
   {
       ComBuffer = SB;
       ComPort = Port;
   }

   public void run()
   {
               int c;
               try
               {
                       FileReader in = new FileReader(ComPort);

while (true)
           {
               c = in.read();
               ComBuffer.PutChar(c);
           }
               try
               {
                       FileReader in = new FileReader(ComPort);
               while (true)
           {
               c = in.read();

               ComBuffer.PutChar(c);
           }
       } catch (IOException e) {}
   }
}

/*
*
* SerialBuffer.java 1.0
* Class that implements the serial buffer
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
*   American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu

*
*/

public class SerialBuffer
{
   private String Content = "";
   private String CurrentMsg, TempContent;
   private boolean available = false;

   public synchronized String GetMsg()
   {
       int SepMark;

       if ((SepMark = Content.indexOf('*')) == -1)
       {
               available = false;
               while (available == false)
               {
               try
               {
                   wait();
               } catch (InterruptedException e) { }
               }
               SepMark = Content.indexOf('*');
       }

       CurrentMsg = Content.substring(0, SepMark);
       TempContent = Content.substring(SepMark+1);
       Content = TempContent;
       notifyAll();
       return CurrentMsg;
   }

   public synchronized void PutChar(int c)
   {
       Character d = new Character((char) c);
       Content = Content.concat(d.toString());
       if (c == '*')
       {
               available = true;
       }
       notifyAll();
   }
}

/*
*
* WriteSerial.java 1.0
* Program to send a character to the serial port
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu
*
*/

import java.io.*;

public class WriteSerial extends Thread
{
   private SerialBuffer ComBuffer;
   private File ComPort;

   public WriteSerial(File Port)
   {
       ComPort = Port;
   }

   public void run()
   {
               int c;
               try
               {
                       FileWriter out = new FileWriter(ComPort);
               while (true)
           {
               out.write('*');
           }
       } catch (IOException e)
       {
               System.out.println(e.getMessage());
       }
   }
}

import java.io.*;

public class SendCom
{
   public static void main(String[] args)
   {

               File OutFile = new File("SEND.TXT");
               File ComPort = new File("COM2");

               int c;

               try
               {
                       FileReader in = new FileReader(OutFile);
                       FileWriter out = new FileWriter(ComPort);
                       while ((c = in.read()) != -1)
                               out.write(c);
                       in.close();
                       out.close();
               } catch (IOException e) {}

       }
}

 

SEND.TXT*

This is a sample of the data file for program testing. *

It should be in the same directory as the SendCom.class file.*

When you run this sample program, connect your COM1 and COM2 with a
serial cable so that you can test this program on one machine. If
you have two machines, you can connect the two machine via a serial
cable and test it. Modified the definition of ComPort in the program
if necessary. *

Thank you for testing this program. If you have any suggestions please
kindly let me know. *

这是一个通过JAVA的扩展包(javax.comm)从串口读取值的类，
  本类库(javax.comm)主要包括：
 SerialBean.java (与其他应用程序的接口),
 SerialBuffer.java (用来保存从串口所接收数据的缓冲区),
 ReadSerial.java (从串口读取数据的程序)。

 整个类的设计思路大概就是：
 实现一个线程一直在监听串口中是否有数据传送过来，
 如果有的话开始拍照，并取得照片后，直接打印出来。因为涉及到商业秘密，所以拍照函数和取得照片函数采用的是空函数，请见谅!
 若要运行此函数必须下载该扩展包，并加载到你的CLASSPATH下。当然，你若要测试并运行此类的话。可能要花费不少的精力。
 如果你只有一台机器，你可以利用一条RS-232电缆将COM1和COM2连接起来，在COM1上运行SerialExample，在COM2上运行Windows提供的超级终端程序。
 如果你有两台机器的话，你可以利用一条RS-232电缆将两台机器的COM1(或者是COM2)连接起来，在一端运行例程，另外一端运行Windows提供的超级终端程序。
 
该类有相当详细的注释。我想应该不难理解吧!

import java.io.*;
import java.awt.*;
import java.awt.print.*;
import javax.print.*;
import javax.comm.*; //这是一个Java扩展类库，并不包括在标准的Java SDK当中。
//如果你尚未安装这个扩展类那么你需要到sun公司的Java站点下载这个类库

class SuanKou implements Runnable{
  private java.io.FileOutputStream fos=null;
  private Thread th=null;
  private long shiJian=500;//设置间隔的时间
   //private int duanKou=1;//设置端口号
   private String Msg = null;
   private SerialBean SB=null;
   private int isSucces=-1;
 
   //构造函数
  public SuanKou(long sj,int dk) {
    System.out.println("构造函数");
    try{
    fos=new java.io.FileOutputStream("c:\\log.txt");
   
    this.shiJian=sj;//设定监听端口的时间
   
    //this.duanKou=dk;//端口号
   
    SB = new SerialBean(dk);//创建一个接口对象，参数为端口号
   
   isSucces = SB.Initialize();//初使化所指定的串口并返回初始化结果。如果初始化成功返回1，否则返回-1
  
    th=new Thread(this);//创建一个线程对象
  
    th.start();//创建SuanKou这个对象就开始启动线程
 }catch(java.io.FileNotFoundException fe){
  fe.printStackTrace();
 }catch(Exception e){
  e.printStackTrace();
 }
  }

//拍照函数
  public void snape() {
    System.out.println("拍照函数");
  }

//取得照片函数
  public void getPicture() {
    System.out.println("取得照片函数");

  }
 
  //实现线程接口的RUN方法
  public void run(){
    Thread.sleep(shiJian);
    this.ReadSuanKou();
  }
 
  //定期到串口读取数据和函数，如果能读到数据就调用snape(),getPicture(),函数，写日志，打印
  private void ReadSuanKou() {
  
   //如果初使化成功的话，
    if (isSucces == 1) {
    
      //从串口(缓冲区)中读取指定长度的一个字符串。(500)
     
      try{
      
      Msg = SB.ReadPort(500);

      //如果可以从串口读到数据的话

      if (Msg != null) {
        this.snape();//调用拍照函数
       
        this.getPicture();//调用取得照片函数
       
        java.text.SimpleDateFormat df=new java.text.SimpleDateFormat("EEEE-MMMM-dd-yyyy");

 Date date=new Date();

 String dateFormat=df.format(date);
 
        fos.write(dateFormat.getBytes());//在日志文件中记录当前时间
       
        fos.write(Msg.getBytes());//将读到的数据写到日志文件中
 
  //调用打印方法 注：若要打印，要打印的对象必须实现java.awt.print.Printable接口。即getPicture
 
  //返回的对象必须实现该接口,因为不知道getPicture返回什么对象，故这个打印功能无法实现，不过大概的思路是
 
  /** 1,需要一个打印服务对象。这可通过三种方式实现：
      在jdk1.4之前的版本，必须要实现java.awt.print.Printable接口
      或通过Toolkit.getDefaultToolkit().getPrintJob来获取打印服务对象；
      在jdk1.4中则还可以通过javax.print.PrintSerivceLookup来查找定位一个打印服务对象。

　　                2、需要开始一个打印工作。这也有几种实现方法：在jdk1.4之前可以通过java.awt.print.PrintJob
   （jdk1.1提供的，现在已经很少用了）调用print或printAll方法开始打印工作；
   也可以通过java.awt.print.PrinterJob的printDialog显示打印对话框，
   然后通过print方法开始打印；在jdk1.4中则可以通过javax.print.ServiceUI的printDialog显示打印对话框，
   然后调用print方法开始一个打印工作。
 
  根据以上的提示去做，不会很难!
  */
 
  java.awt.print.PrinterJob pj=new java.awt.print.PrinterJob();
 
  pj.printDialog();//显示打印对话框
  pj.print();//开始打印
 
      }

      //SB.WritePort("OK");若要向串口返回一个结果可以调用该函数?

     
 }catch(Exception e){
 
  e.printStackTrace();

 }finally{
  try{
   fos.close();
    //停止串口检测进程并关闭串口。
        SB.ClosePort();
     
  }catch(Exception e){
   e.printStackTrace();
  }
 }

    }
    else {
      throw RuntimeException("读取串口数据时出错!");
    }

  }

 

  //主函数
  public static void main(String args[]) {
  
    new SuanKou(1000,1);//参数为间隔的时间,和端口号

  }
}

 

本文介绍一个利用Java Comm API (javax.comm)实现串口全双工通讯的简单程序。这个程序首先打开并初始化一个串口，然后启动如下三个进程：ReadSerial进程从该串口读取数据并放入缓冲区，ReadBuffer进程从缓冲区读取数据并打印到屏幕， WriteSerial进程每5秒钟向该串口发送一个星号(*)。

在这个示例程序中使用了一个简单的协议，既不同的消息之间用星号'*'作为分隔。缓冲区程序根据是否收到星号作为存在等待处理的消息的判断依据。

Java Comm API不是标准的Java API，因此的标准的运行环境中并不提供这个包。如果你的系统上还没有安装这个包，你可以从SUN公司的网站下载。在这个包里面有一个安装指南，如果你没有正确安装这个包，可能你不能够正确运行这个例程。

这个简单的例程包括以下文件：

IMU.java (主程序)
ReadBuffer.java (从缓冲区读取一个消息)
ReadSerial.java (读取串口数据并放入缓冲区)
SerialBuffer.java (缓冲区)
WriteSerial.java (每5秒钟往串口送一个星号'*')

测试程序：

SendCom.java (将一个数据文件往串口发送)
SEND.TXT (供测试用的数据文件)

测试方法：

1 正确安装Java Comm API后编译本例程
2 将计算机的COM1和COM2用一条串口线连接起来
3 运行IMU。如果你这时候打开Windows自带的超级终端并连接到COM2的话，你应该能够看见有星号出现在超级终端的屏幕上。超级终端的参数设置为9600, N, 8, 1, none。
4 关闭超级终端，运行SendCom。这时候你应该能够从IMU的屏幕上看到数据文件里面的内容。

/*
*
* IMU.java 1.0
* Main Program for Serial Communication
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu
*
*/

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

class IMU
{

static CommPortIdentifier portId;
static SerialPort serialPort;
static OutputStream out;
static InputStream in;

public static void main(String[] args)
{

try
{

//Declare the serial port, and open it.

portId = CommPortIdentifier.getPortIdentifier("COM1");
try
{

serialPort = (SerialPort) portId.open("IMU_App", 2000);

} catch (PortInUseException e)
{

System.out.println(e.getMessage());

}

//Use InputStream in to read from the serial port, and OutputStream
//out to write to the serial port.

try
{

in = serialPort.getInputStream();
out = serialPort.getOutputStream();

} catch (IOException e)
{

System.out.println(e.getMessage());

}

//Initialize the communication parameters to 9600, 8, 1, none.

try
{

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

} catch (UnsupportedCommOperationException e)
{

System.out.println(e.getMessage());

}

} catch (NoSuchPortException e)
{

System.out.println(e.getMessage());

}

//Declare the serial buffer area, a thread to read from the seriial port,
//a thread to read from the serial buffer for processing, and a thread
//to write to the serial port.

SerialBuffer SB = new SerialBuffer();
ReadSerial r1 = new ReadSerial(SB, in);
ReadBuffer r2 = new ReadBuffer(SB);
WriteSerial r3 = new WriteSerial(out);

//Start all three threads.

r1.start();
r2.start();
r3.start();

}

}

/*
*
* SerialBuffer.java 1.0
* Class that implements the serial buffer
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu
*
*/

public class SerialBuffer
{

private String Content = "";
private String CurrentMsg, TempContent;
private boolean available = false;


//read a message from the serial buffer. The star character '*' is used
//as the seperation mark between different messages.

public synchronized String GetMsg()
{

int SepMark;

if ((SepMark = Content.indexOf('*')) == -1)
{

available = false;
while (available == false)
{

try
{
        wait();
} catch (InterruptedException e) { }

}
SepMark = Content.indexOf('*');

}

CurrentMsg = Content.substring(0, SepMark);
TempContent = Content.substring(SepMark+1);
Content = TempContent;
notifyAll();
return CurrentMsg;

}

//Put a character to the serial buffer

public synchronized void PutChar(int c)
{

Character d = new Character((char) c);
Content = Content.concat(d.toString());
if (c == '*')
{
        available = true;
}
notifyAll();

}

}

/*
*
* ReadSerial.java 1.0
* Program to read characters from the serial port and put it
* to the buffer
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu
*
*/

import java.io.*;

public class ReadSerial extends Thread
{

private SerialBuffer ComBuffer;
private InputStream ComPort;

public ReadSerial(SerialBuffer SB, InputStream Port)
{
        ComBuffer = SB;
        ComPort = Port;
}

public void run()
{

int c;
try
{

while (true)
{
        c = ComPort.read();
        ComBuffer.PutChar(c);
}

} catch (IOException e) {}

}

}

/*
*
* ReadBuffer.java 1.0
* Program to Read the Serial Buffer
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu
*
*/

import java.io.*;

public class ReadBuffer extends Thread
{

private SerialBuffer ComBuffer;

public ReadBuffer(SerialBuffer SB)
{
        ComBuffer = SB;
}

public void run()
{

String Msg;
while (true)
{
        Msg = ComBuffer.GetMsg();
        System.out.println(Msg);
}

}

}

/*
*
* WriteSerial.java 1.0
* Program to send a star to the serial port every 5 seconds.
*
* Created: March 27, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
* qjiang@tsinghua.edu
*
*/

import java.io.*;

public class WriteSerial extends Thread
{

private SerialBuffer ComBuffer;
private OutputStream ComPort;

public WriteSerial(OutputStream Port)
{
        ComPort = Port;
}

public void run()
{

int c;
try
{

while (true)
{

ComPort.write('*');
try
{
        wait(5000);
} catch (InterruptedException e) { }

}

} catch (IOException e)
{
        System.out.println(e.getMessage());
}

}

}

/*
*
* SendCom.java 1.0
*
* Project: Java Based Information Exchange Support System
* Onboard Plug-in System
* Sending data through serial port
*
* Created: March 15, 2001
*
* Author : Qingye Jiang (John)
* American GNC Corporation
* 888 Easy St, Simi Valley CA 93065-1812
*
* Contact: (805) 582-0582 (Tel), (805) 582-0098 (Fax)
*
*/

import java.io.*;

public class SendCom
{

public static void main(String[] args)
{

File OutFile = new File("SEND.TXT");
File ComPort = new File("COM2");

int c;

try
{

FileReader in = new FileReader(OutFile);
FileWriter out = new FileWriter(ComPort);
while ((c = in.read()) != -1)
        out.write(c);
in.close();
out.close();

} catch (IOException e) {}

}

}

SEND.TXT*

This is a sample of the data file for program testing. *

It should be in the same directory as the SendCom.class file.*

When you run this sample program, connect your COM1 and COM2 with a
serial cable so that you can test this program on one machine. If
you have two machines, you can connect the two machine via a serial
cable and test it. Modified the definition of ComPort in the program
if necessary. *

Thank you for testing this program. If you have any suggestions please
kindly let me know. *

小结:

在上面的例程中，大多数的程序仅对我前天发的《一个使用Java读取串口的程序》
一文做了小篇幅的改动，有几个程序和数据文件都没有改动。但是为了本文的完整
性，仍然将雷同的内容也贴了一遍，还望斑竹多多见谅。

这个例程和前面一个例程的区别在于前面一个例程使用了文件IO，而本例程使用了
Comm API。在C语言里面用fopen()函数来打开串口是可读也可写的，但是在Java里
面声明了File以后并不立即打开文件，文件是在声明FileReader或者FileWriter时
才打开的。由于串口不能同时被打开两次，所以读操作和写操作不能够同时进行，
不能够实现全双工通讯。

Comm API虽然能够实现全双工通讯，但是由于它不是标准的Java API，代码的可移
植性难以保证。如果程序并不要求实现全双工的话，我认为利用文件操作不失为一
个好办法。