Java / Arduino-从串行端口读取数据
我有一个Java程序，必须读取Arduino发送的信息。我从这里获取了Java代码。现在，我不太了解它是如何工作的，但是我尝试对其进行修改，并且得到了以下信息：
import java.io.BufferedReader;import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent;
import gnu.io.SerialPortEventListener;
import java.util.Enumeration;
public class Serial implements SerialPortEventListener {
SerialPort serialPort;
private static final String PORT_NAMES[] = {
"/dev/tty.usbserial-A9007UX1", // Mac OS X
"/dev/ttyUSB0", // Linux
"COM3", // Windows
};
private BufferedReader input;
private static OutputStream output;
private static final int TIME_OUT = 2000;
private static final int DATA_RATE = 115200;
public void initialize() {
CommPortIdentifier portId = null;
Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();
while (portEnum.hasMoreElements()) {
CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
for (String portName : PORT_NAMES) {
if (currPortId.getName().equals(portName)) {
portId = currPortId;
break;
}
}
}
if (portId == null) {
System.out.println("Could not find COM port.");
return;
}
try {
serialPort = (SerialPort) portId.open(this.getClass().getName(),TIME_OUT);
serialPort.setSerialPortParams(DATA_RATE, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
output = serialPort.getOutputStream();
serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);
}
catch (Exception e) {
System.err.println(e.toString());
}
}
public synchronized void serialEvent(SerialPortEvent oEvent) {
if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
String inputLine=input.readLine();
System.out.println(inputLine);
} catch (Exception e) {
System.err.println(e.toString());
}
}
}
public synchronized void close() {
if (serialPort != null) {
serialPort.removeEventListener();
serialPort.close();
}
}
public Serial(String ncom){
if(Integer.parseInt(ncom)>=3 && Integer.parseInt(ncom)<=9)
PORT_NAMES[2] = "COM" + ncom;
initialize();
Thread t=new Thread() {
public void run() {
try {Thread.sleep(1000000);} catch (InterruptedException ie) {}
}
};
t.start();
System.out.println("Serial Comms Started");
}
public synchronized void send(int b){
try{
output.write(b);
}
catch (Exception e) {
System.err.println(e.toString());
}
}
public synchronized int read(){
int b = 0;
try{
b = (int)input.read();
}
catch (Exception e) {
System.err.println(e.toString());
}
return b;
}
}
我创建一个对象串行COM口，我需要在主程序，然后我使用Serial.read和Serial.write当我需要它。
Serial.write效果很好，Arduino获取数据并将其显示在LCD显示屏中。问题是Serial.read。程序运行时，它会不断从串行端口读取数据（大约每40毫秒一次），但这并不意味着Arduino发送了一些信息。Arduino仅在按下按钮时才发送字节。因此，当Java代码运行时，它会在读取某些内容之前引发“
n”异常，这会导致很大的延迟。
我知道我需要类似的东西Serial.available()，我试过了input.available()，但是不起作用。我不知道如何解决这个问题。
如果您有能正常工作的代码，那么如果您能给我，我将非常感激。我只需要两种方法，读写，我不在乎代码如何工作：D
编辑：
我更改了Serial类，现在它又如前文所述具有此方法
public synchronized void serialEvent(SerialPortEvent oEvent) { if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
String inputLine=null;
if (input.ready()) {
inputLine = input.readLine();
panel.read(inputLine);
}
} catch (Exception e) {
System.err.println(e.toString());
}
}
}
在另一堂课（在本例中为面板）中，我得到了：
public void read(String data){ System.out.println(data);
System.out.println(data == "255");
if(data == "255")
//code here
}
它可以正确打印值，但data == "255"即使我确实得到255 …，也总是错误的Integer.parseInt。为什么要死？
编辑2：好解决了：
public void read(String data){ serialRead = Integer.parseInt(data);
if(serialRead == 255)
//code here
}
现在它正在工作..不知道为什么我必须这样做…无论如何:)
回答：
您不想专门编写示例代码中已经存在的读取函数，如TheMerovingian指出的，您可以在读取之前检查输入Buffer，这是我在一个项目中使用的工作代码。
import java.io.BufferedReader;import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent;
import gnu.io.SerialPortEventListener;
import java.util.Enumeration;
public class SerialTest implements SerialPortEventListener {
SerialPort serialPort;
/** The port we're normally going to use. */
private static final String PORT_NAMES[] = { "/dev/tty.usbserial-A9007UX1", // Mac OS X
"/dev/ttyUSB0", // Linux
"COM35", // Windows
};
private BufferedReader input;
private OutputStream output;
private static final int TIME_OUT = 2000;
private static final int DATA_RATE = 9600;
public void initialize() {
CommPortIdentifier portId = null;
Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();
//First, Find an instance of serial port as set in PORT_NAMES.
while (portEnum.hasMoreElements()) {
CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
for (String portName : PORT_NAMES) {
if (currPortId.getName().equals(portName)) {
portId = currPortId;
break;
}
}
}
if (portId == null) {
System.out.println("Could not find COM port.");
return;
}
try {
serialPort = (SerialPort) portId.open(this.getClass().getName(),
TIME_OUT);
serialPort.setSerialPortParams(DATA_RATE,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
// open the streams
input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
output = serialPort.getOutputStream();
serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);
} catch (Exception e) {
System.err.println(e.toString());
}
}
public synchronized void close() {
if (serialPort != null) {
serialPort.removeEventListener();
serialPort.close();
}
}
public synchronized void serialEvent(SerialPortEvent oEvent) {
if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
String inputLine=null;
if (input.ready()) {
inputLine = input.readLine();
System.out.println(inputLine);
}
} catch (Exception e) {
System.err.println(e.toString());
}
}
// Ignore all the other eventTypes, but you should consider the other ones.
}
public static void main(String[] args) throws Exception {
SerialTest main = new SerialTest();
main.initialize();
Thread t=new Thread() {
public void run() {
//the following line will keep this app alive for 1000 seconds,
//waiting for events to occur and responding to them (printing incoming messages to console).
try {Thread.sleep(1000000);} catch (InterruptedException ie) {}
}
};
t.start();
System.out.println("Started");
}
}
编辑：serialEvent函数负责读取缓冲区。
public synchronized void serialEvent(SerialPortEvent oEvent) { if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
String inputLine=null;
if (input.ready()) {
inputLine = input.readLine();
System.out.println(inputLine);
}
} catch (Exception e) {
System.err.println(e.toString());
}
}
// Ignore all the other eventTypes, but you should consider the other ones.
}
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