我最近一直致力于java和arduino之间的沟通，因为我有一个需要它的项目，所以我已经阅读了很多关于它的内容，并开始在其中取得一些进展，例如从java并在arduino中读取并使用它然后再次向java发送输出，反正之后我必须在java中设置一个滑块所以我可以在移动它时将0到1023之间的值发送到arduino但问题开始出现在这里，我创建了滑块（使用JSlider）并使用stateChanged方法将值发送到arduino，然后arduino应该读取数据并向java报告，我将MinorTickSpacing设置为100，因此每当您单击滑块时它从0到100，因此，arduino正确读取数据（它读取3次，我不知道为什么），直到它达到300这是我在java中看到的输出（使用serialEvent读取arduino的输出和BufferReader）：
COM port found:COM3
Port open succesful: COM3
100
100
200
200
200
44
44
44
65533
65533
65533
244
244
我在滑块上点击了5次，所以它应该是100,200,300,400和100。 500，但我看到那些奇怪的数字，我不知道为什么。 这是我的Java程序（二手RXTX库和Eclipse IDE）和Arduino的。
Java程序：
import java.io.BufferedReader; //BufferedReader makes reading operation efficient
import java.io.IOException;
import java.io.InputStreamReader; //InputStreamReader decodes a stream of bytes into a character set
import java.io.OutputStream; //writes stream of bytes into serial port
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent; //deals with possible events in serial port (eg: data received)
import gnu.io.SerialPortEventListener; //listens to the a possible event on serial port and notifies when it does
import java.util.Enumeration;
import gnu.io.PortInUseException; //all the exceptions.Never mind them for now
import gnu.io.UnsupportedCommOperationException;
import java.util.Scanner; //to get user input of name
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.event.*;
public class TestingGUI implements SerialPortEventListener,ActionListener, ChangeListener {
private SerialPort serialPort ; //defining serial port object
private CommPortIdentifier portId = null; //my COM port
private static final int TIME_OUT = 2000; //time in milliseconds
private static final int BAUD_RATE = 9600; //baud rate to 9600bps
private BufferedReader input; //declaring my input buffer
private OutputStream output; //declaring output stream
private String name; //user input name string
public static String status;
JFrame frame;
JPanel panel;
JLabel label,label1;
JSlider slide;
JProgressBar progress;
JButton onButton,offButton,blinkButton;
Scanner inputName; //user input name
public TestingGUI()
{
frame = new JFrame();
frame.setSize(700, 150);
frame.setTitle("Arduino Test");
panel = new JPanel();
frame.add(panel);
slide = new JSlider();
slide.setMinimum(0);
slide.setMajorTickSpacing(5);
slide.setMaximum(1023);
slide.setMinorTickSpacing(100);
slide.setPaintLabels(true);
slide.setPaintTicks(true);
slide.setSnapToTicks(true);
slide.setToolTipText("Move the slider to desired location.");
slide.setValue(0);
slide.setValueIsAdjusting(true);
slide.addChangeListener(this);
panel.setLayout(null);
slide.setBounds(10,10, 650, 50);
panel.add(slide);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
//method initialize
private void initialize()
{
CommPortIdentifier ports = null; //to browse through each port identified
Enumeration portEnum = CommPortIdentifier.getPortIdentifiers(); //store all available ports
while(portEnum.hasMoreElements()) //browse through available ports
{
ports = (CommPortIdentifier)portEnum.nextElement();
//following line checks whether there is the port i am looking for and whether it is serial
if(ports.getPortType() == CommPortIdentifier.PORT_SERIAL&&ports.getName().equals("COM3"))
{
System.out.println("COM port found:COM3");
portId = ports; //initialize my port
break;
}
}
//if serial port am looking for is not found
if(portId==null)
{
System.out.println("COM port not found");
System.exit(1);
}
}
//end of initialize method
//connect method
private void portConnect()
{
//connect to port
try
{
serialPort = (SerialPort)portId.open(this.getClass().getName(),TIME_OUT); //down cast the comm port to serial port
//time to wait
System.out.println("Port open succesful: COM3");
//set serial port parameters
serialPort.setSerialPortParams(BAUD_RATE,SerialPort.DATABITS_8,SerialPort.STOPBITS_1,SerialPort.PARITY_NONE);
}
catch(PortInUseException e){
System.out.println("Port already in use");
System.exit(1);
}
catch(NullPointerException e2){
System.out.println("COM port maybe disconnected");
}
catch(UnsupportedCommOperationException e3){
System.out.println(e3.toString());
}
//input and output channels
try
{
input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
output = serialPort.getOutputStream();
//adding listeners to input and output streams
serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);
serialPort.notifyOnOutputEmpty(true);
//defining reader and output stream
}
catch(Exception e){
System.out.println(e.toString());
}
}
//end of portConncet method
@Override
public void stateChanged(ChangeEvent e)
{
if(e.getSource() == slide)
{
try {
int out = slide.getValue();
output.write(out);
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
@Override
public void actionPerformed(ActionEvent event) {
}
//readWrite method
@Override
public void serialEvent(SerialPortEvent evt)
{
if (evt.getEventType() == SerialPortEvent.DATA_AVAILABLE) //if data available on serial port
{
try {
if(input.ready())
{
int testInt = input.read();
System.out.println(testInt);
}
} catch (Exception e)
{
System.err.println(e.toString());
}
}
}
//end of serialEvent method
//main method
public static void main(String[] args)
{
TestingGUI myTest = new TestingGUI(); //creates an object of the class
myTest.initialize();
myTest.portConnect();
}//end of main method
}// end of SerialTest
和Arduino计划：
void setup() {
Serial.begin(9600);
pinMode(13,OUTPUT);
}
void loop() {
while(Serial.available() == 0)
{
}
int test2 = Serial.read();
Serial.write(test2);
}
我应该怎么做才能获得正确的数字并超过arduino所显示的限制？ （显然只能正确读取0到255之间的数字）
答案 0 :(得分：0)
根据Arduino In this downloaded only one image.文档：https://www.arduino.cc/en/Serial/Read调用它返回：
可用的传入串行数据的第一个字节（如果没有可用的数据，则为-1） - int
根据定义，一个字节的值可以在0到225之间，这就是这些值正常工作的原因。
当你发送300的值时，你会遇到一些名为＆＃34;算术溢出＆＃34; - 想象你从0到300计数，但在255你再从0开始，然后你达到44.同样适用于500.
我不确定为什么你得到65533为400，它应该是144（400 modulo 256）。如果我发现，我会更新答案。
总结 - 你不应该发送或期望0-255范围之外的值。如果要发送更大的数字，请将其分成字节并在通信通道的另一侧汇回。