How to connect Serial Port with JAVA

Serial Port Programming

In Java , we commonly use RxTx library for serial programming..

2 Important Things to do:

·         Add RxTx jar into our project..

·         Copy RxTx serial.dll,RxTxParallel into c:\program files\java\jre\bin

To start coding import gnu.io.*…..

Steps:   1) Get Port

               2) Open it & initialize

               3) Starting i/p & o/p stream

               4) Adding event listener to listen for incoming data..

               5) Read

               6) Write

               7) Close

1 ) Get Port

Jobs

◦Search or specify desired port

◦Check Usage status

◦Open and Reserve it

—Class javax.comm.CommPortIdentifier

◦public static Enumeration getPortIdentifiers();

◦public static CommPortIdentifier getPortIdentifier(String portName);

◦public boolean isCurrentlyOwned();

◦public String getPortName();

◦public int getPortType();

–PORT_SERIAL or PORT_PARALLEL

Program Code:

 public void searchPort()

{int i=0;

String []r=new String(5);

Enumeration e=CommPortIdentifier.getPortIdentifiers();

  while(e.hasMoreElements())

{

CommPortIdentifier cpi=(CommPortIdentifier)e.nextElement ();

If((cpi.getPortType()==CommPortIdentifier.PORT_SERIAL)&&(cpi.isCurrentlyOwned==false))

{

   r[i]= cpi.getName();

i++;

}

 return r;}

2)Open  Port

Jobs :

◦Open and reserve it

—Class javax.comm.CommPortIdentifier

◦public CommPort open(

String appName,// Reservation Name

int timeout// block waiting for port open (MS)

);

—Class javax.comm.CommPort

Program Code:

 public CommPort openCommPort(String portName, String apname, int TIMEOUT){

CommPort cp=null;

try{

cpi=(CommPortIdentifier)r.get(portName);}

catch(NoSuchPortException a)

{

}

  try{

//return object of type CommPort

Cp=cpi.open(“apName”,TIMEOUT);

Sp=(SerialPort)cp ;       //cast CommPort objt to Serial Port objt}

 catch(PortInUseException s)

{

}

 open() :                          *    Main method

·         Instructs the program to open port which is stored in CommPort object

·         Then the object casted as a Serial port object for accessing methods and variables specific to serial port class.

Intialize Parameters:

·        Either we can individually set..

·        Or set them using Serialport setParams method..

—Jobs

◦Initialization

–Baud-Rate, Data Bits, Stop Bits, Parity, flow control

—Class CommPort

◦public abstract void setSerialPortParams(

int baudrate,

int databits, // DATABITS_8, DATABITS_7, …

int stopbits,// STOPBITS_1, STOPBITS_1_5, …

int parity// PARITY_NONE, PARITY_ODD, …

);

◦public abstract void setFlowControlMode(

int flowcontrol// FLOWCONTROL_NONE,

// FLOWCONTROL_RTSCTS_IN,

// FLOWCONTROL_RTSCTS_OUT, …

·         Baud rate  - transmission rate of signals..

·         Start bit     - logical 0 to indicate receiver to start scanning

·         Data bit     - actual data

·         Parity bit    - for error detection

·         Stop bit      - Clock cycle needed to complete transmission

Code:

sp.setSerialPortParams(9600,SerialPort.DATABITS_8,SerialPort.STOPBITS_1,Seria   lPort.PARITY_NONE);     

3) Starting i/p & o/p stream

—Jobs

◦Use InputStreaming and OutputStreaming of CommPort object to do I/O

Code:

      OutputStream out=sp.getOutputStream();

      InputStream in=sp.getInputStream();

The streams are initialized by returning the input output streams of open serial port.

4)Setting up Event Listeners to Read data

·        Once the port is open,serial port must know whenever there is a data to be read .

·        In event driven approach, when the event is hit,a special block of code will run

·        Class needs to implement serialevent listener..

·        The base class have a method called serialEvent(event)that should be overridden before event code will work.

·        Overriiden defines what happens when the event is hit.

·        addEventlistener(this)-is the event that is always checking for Serial Event.

Code:

sp.addEventListener(this);

5) Reading Data

Public void serialEvent(serialPortEvent evt)

{

If(evt.getEventType()==SerialPortEvent.DATA_AVAILABLE)

{

 try{ byte[] temp;

int  length;

while(length==in.available())

{

 temp=new  byte[]length;

in.read(temp,0,length);

buffer.add(temp);

}

}

6. Write data

  public void writeData(CommPort cp,byte[]data)

{

 try {

out.write(data);

out.flush();

}

}

 Program Code Eg:

Output out=sp.getOutputStream();

String s=”ABCD”

System.out.println(“Begin to write”);

Byte[]data=s.getBytes();

 for(int i=0;i<data.length;i++)

{

 out.write(data[i]);

out.flush();

}

7)Close Connection

 public void disconnect()

{ sp.removeEventListener();

sp.close();

in.close();out.close();}

 Serial Port Programming

In Java , we commonly use RxTx library for serial programming..

2 Important Things to do:

·         Add RxTx jar into our project..

·         Copy RxTx serial.dll,RxTxParallel into c:\program files\java\jre\bin

To start coding import gnu.io.*…..

Steps:   1) Get Port

               2) Open it & initialize

               3) Starting i/p & o/p stream

               4) Adding event listener to listen for incoming data..

               5) Read

               6) Write

               7) Close

1 ) Get Port

Jobs

◦Search or specify desired port

◦Check Usage status

◦Open and Reserve it

—Class javax.comm.CommPortIdentifier

◦public static Enumeration getPortIdentifiers();

◦public static CommPortIdentifier getPortIdentifier(String portName);

◦public boolean isCurrentlyOwned();

◦public String getPortName();

◦public int getPortType();

–PORT_SERIAL or PORT_PARALLEL

Program Code:

 public void searchPort()

{int i=0;

String []r=new String(5);

Enumeration e=CommPortIdentifier.getPortIdentifiers();

  while(e.hasMoreElements())

{

CommPortIdentifier cpi=(CommPortIdentifier)e.nextElement ();

If((cpi.getPortType()==CommPortIdentifier.PORT_SERIAL)&&(cpi.isCurrentlyOwned==false))

{

   r[i]= cpi.getName();

i++;

}

 return r;}

2)Open  Port

Jobs :

◦Open and reserve it

—Class javax.comm.CommPortIdentifier

◦public CommPort open(

String appName,// Reservation Name

int timeout// block waiting for port open (MS)

);

—Class javax.comm.CommPort

Program Code:

 public CommPort openCommPort(String portName, String apname, int TIMEOUT){

CommPort cp=null;

try{

cpi=(CommPortIdentifier)r.get(portName);}

catch(NoSuchPortException a)

{

}

  try{

//return object of type CommPort

Cp=cpi.open(“apName”,TIMEOUT);

Sp=(SerialPort)cp ;       //cast CommPort objt to Serial Port objt}

 catch(PortInUseException s)

{

}

 open() :                          *    Main method

·         Instructs the program to open port which is stored in CommPort object

·         Then the object casted as a Serial port object for accessing methods and variables specific to serial port class.

Intialize Parameters:

·        Either we can individually set..

·        Or set them using Serialport setParams method..

—Jobs

◦Initialization

–Baud-Rate, Data Bits, Stop Bits, Parity, flow control

—Class CommPort

◦public abstract void setSerialPortParams(

int baudrate,

int databits, // DATABITS_8, DATABITS_7, …

int stopbits,// STOPBITS_1, STOPBITS_1_5, …

int parity// PARITY_NONE, PARITY_ODD, …

);

◦public abstract void setFlowControlMode(

int flowcontrol// FLOWCONTROL_NONE,

// FLOWCONTROL_RTSCTS_IN,

// FLOWCONTROL_RTSCTS_OUT, …

·         Baud rate  - transmission rate of signals..

·         Start bit     - logical 0 to indicate receiver to start scanning

·         Data bit     - actual data

·         Parity bit    - for error detection

·         Stop bit      - Clock cycle needed to complete transmission

Code:

sp.setSerialPortParams(9600,SerialPort.DATABITS_8,SerialPort.STOPBITS_1,Seria   lPort.PARITY_NONE);     

3) Starting i/p & o/p stream

—Jobs

◦Use InputStreaming and OutputStreaming of CommPort object to do I/O

Code:

      OutputStream out=sp.getOutputStream();

      InputStream in=sp.getInputStream();

The streams are initialized by returning the input output streams of open serial port.

4)Setting up Event Listeners to Read data

·        Once the port is open,serial port must know whenever there is a data to be read .

·        In event driven approach, when the event is hit,a special block of code will run

·        Class needs to implement serialevent listener..

·        The base class have a method called serialEvent(event)that should be overridden before event code will work.

·        Overriiden defines what happens when the event is hit.

·        addEventlistener(this)-is the event that is always checking for Serial Event.

Code:

sp.addEventListener(this);

5) Reading Data

Public void serialEvent(serialPortEvent evt)

{

If(evt.getEventType()==SerialPortEvent.DATA_AVAILABLE)

{

 try{ byte[] temp;

int  length;

while(length==in.available())

{

 temp=new  byte[]length;

in.read(temp,0,length);

buffer.add(temp);

}

}

6. Write data

  public void writeData(CommPort cp,byte[]data)

{

 try {

out.write(data);

out.flush();

}

}

 Program Code Eg:

Output out=sp.getOutputStream();

String s=”ABCD”

System.out.println(“Begin to write”);

Byte[]data=s.getBytes();

 for(int i=0;i<data.length;i++)

{

 out.write(data[i]);

out.flush();

}

7)Close Connection

 public void disconnect()

{ sp.removeEventListener();

sp.close();

in.close();out.close();}