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();}
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