JAVA编程中串口通信的方法介绍

以前经常用C语言操作串口，实现一些发送接收之类的小功能，最近项目中也用到了串口通信，不过语言变成了Java，这个搞起来略蛋疼。

Java说起来就是各种库各种引用，所以得到某些需求先google搜一把~~比如之前搞半天的读取网页内容，自己边琢磨边写，又是 charset，又是proxy，又是什么browsertype的，晕头转向，最后拿Jsoup一会儿就搞定了……不过使用之前要充分考虑可扩展性和 API的丰富程度，不然后面程序体积变大集成起来很蛋疼。好了废话不说，讲讲串口的问题……

总述

Java常用的(我用到的)串口工具有俩：javacomm和RXTX，前者只支持win32，后者32和64位和其他版本都有。使用方法类似，所以就放到一起说：

下载到压缩包会看到readme之类的提示，然后把对应的dll文件和jar文件分别拷贝到/bin和/lib目录下，然后在出问题的时候继续查看readme。接着跑一下附带的例程。

具体使用过程就是：配置端口波特率、校验位等信息;打开串口;写数据;读输出;关闭。这一系列步骤在写程序的时候一定不要弄颠倒了。

串口配置

需要配置的有4项：

波特率(baudrate)– 一般9600、115200即可

(数据位)dataBits– 一般8 bits

DATABITS_5: 5 bits

DATABITS_6: 6 bits

DATABITS_7: 7 bits

DATABITS_8: 8 bits

(停止位)stopBits —— 一般1 stop bit

STOPBITS_1: 1 stop bit

STOPBITS_2: 2 stop bits

STOPBITS_1_5: 1.5 stop bits

(校验位)parity —— 不需校验位的话，选择SerialPort.PARITY_NONE

PARITY_NONE: no parity

PARITY_ODD: odd parity

PARITY_EVEN: even parity

PARITY_MARK: mark parity

PARITY_SPACE: space parity

流量控制模式(FlowControlMode) —— 一般FLOWCONTROL_NONE

FLOWCONTROL_NONE: no flow control

FLOWCONTROL_RTSCTS_IN: RTS/CTS (hardware) flow control for input

FLOWCONTROL_RTSCTS_OUT: RTS/CTS (hardware) flow control for output

FLOWCONTROL_XONXOFF_IN: XON/XOFF (software) flow control for input

FLOWCONTROL_XONXOFF_OUT:XON/XOFF (software) flow control for output

事件监听

addEventListener(SerialPortEventListener lsnr)

用于监听串口事件(SerialEvents)，可监听的事件有：

BI(Break interrupt)

CD(Carrier detect)

CTS(Clear to send)

DATA_AVAILABLE(Data available at the serial port)

DSR(Data set ready)

eventType(Deprecated. Replaced by getEventType method)

FE(Framing error)

OE(Overrun error)

OUTPUT_BUFFER_EMPTY(Output buffer is empty)

PE(Parity error)

RI(Ring indicator)

读数据

通过SerialPortEventListener来，读取到DATA_AVAILABLE，保存并处理串口内容。

写数据

使用getOutputStream来向串口发送数据，是发送数据的唯一方法。使用时，向OutPutStream中写入byte串即可，之后用SerialPortEventListener获取回馈结果。

RXTX例程(来自这里 )：

public class USBComm implements SerialPortEventListener {

public static final String MESSAGE = "MESSAGE TO BE SEND";
/**
* Stream for the storage of incoming data
*/
private InputStream inputStream;
/**
* Stream for the dispatching of data
*/
private OutputStream outputStream;
/**
* Timeout of the USB port
*/
private final int PORT_TIMEOUT = 2000;
/**
* Representation of the serial port used for the communication
*/
public SerialPort serialPort;
/**
* Buffer that stores the received bytes from the media
*/
protected LinkedBlockingQueue receivedBytes;

/**
* Builds a new manager for the communication via USB port.
* @exception IOException if an error occurred during the opening of the USB port
*/
public USBComm(String comm) throws IOException {
receivedBytes = new LinkedBlockingQueue(100000);
String port = comm; //place the right COM port here, OS dependent

//Check that the USB port exists and is recognized:
Enumeration portList = CommPortIdentifier.getPortIdentifiers();
boolean portFound = false;
CommPortIdentifier portId = null;
while (portList.hasMoreElements()) {
portId = (CommPortIdentifier) portList.nextElement();
if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
if (portId.getName().equals(port)) {
Log.logAndDisplay(LogLevel.INFO, "SerialConnection", "Found port: " + port);
portFound = true;
break;
}
}
}

if (!portFound)
throw new IOException("port " + port + " not found.");

try {
Log.logAndDisplay(LogLevel.INFO, "SerialConnection", "USB port " + port + " opening...");
serialPort = (SerialPort) portId.open("USBCommunicator", PORT_TIMEOUT);
inputStream = serialPort.getInputStream();
outputStream = serialPort.getOutputStream();
serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);

Thread.sleep(1000);

serialPort.setSerialPortParams(serialPort.getBaudRate(),
serialPort.getDataBits(),
serialPort.getStopBits(),
serialPort.getParity());
serialPort.setFlowControlMode(serialPort.getFlowControlMode());

} catch (Exception e) {
System.err.println(e.getMessage());
throw new IOException(e.getMessage());
}
}

public void closeUSB(){
//close the streams for serial port:
try {
inputStream.close();
outputStream.close();
} catch (IOException e) {
System.err.println("Cannot close streams:" + e.getMessage());
}
}

/**
* Listener for USB events
*
* @param event new event occurred on the USB port
*/
public void serialEvent(SerialPortEvent event){
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:
//nothing to do...
break;

case SerialPortEvent.DATA_AVAILABLE:
byte received = -1;
do {
try {
received = (byte)inputStream.read();
} catch (IOException e) {
System.err.println("Error reading USB:" + e.getMessage());
}

synchronized (receivedBytes) {
try {
receivedBytes.add(received);
} catch (IllegalStateException ew) {
System.err.println(ew.getMessage());
receivedBytes.poll();
receivedBytes.add(received);
}
}
} while(received != -1);

break;
}
}

public void write(byte[] buffer){
try {
outputStream.write(buffer);
//outputStream.flush();
} catch (IOException e) {
System.err.println("Cannot write:" + e.getMessage());
}
}
public static void main(String[] args){
USBComm usb;
try {
usb = new USBComm("COM73"); // change to your port
byte[] b = MESSAGE.getBytes();
usb.write(b);
usb.serialPort.close();
usb.closeUSB();

} catch (IOException e) {
System.err.println("IOException:" + e.getMessage());
}
}
}