java - 使用串行通信在微 Controller 上写入数据时出现问题

Question

我正在尝试使用串行通信向微 Controller 发送命令，我可以编译并运行以下代码而不会出现任何错误，但值未写入寄存器。我做错了什么？

代码

import java.io.*;

import javax.comm.*;

import net.wimpi.modbus.net.SerialConnection;
import net.wimpi.modbus.util.SerialParameters;

import java.util.*;

public class SerTest {

public static void main(String[] args)  {



Enumeration portIdentifiers = CommPortIdentifier.getPortIdentifiers();

CommPortIdentifier portId = null;  
while (portIdentifiers.hasMoreElements())
{
  CommPortIdentifier pid = (CommPortIdentifier) portIdentifiers.nextElement();
  if(pid.getPortType() == CommPortIdentifier.PORT_SERIAL &&
     pid.getName().equals("COM4")) 
  {
      portId = pid;
      break;
  }
}
if(portId == null)
{
  System.err.println("Could not find serial port "); // + wantedPortName);
  System.exit(1);
}

SerialPort port = null;

try {
  port = (SerialPort) portId.open(
      "name", // Name of the application asking for the port 
      10000   // Wait max. 10 sec. to acquire port
  );
} catch(PortInUseException e) {
  System.err.println("Port already in use: " + e);
  System.exit(1);
}

try {
port.setSerialPortParams(

    9600 , SerialPort.DATABITS_8,
    SerialPort.STOPBITS_1,
    SerialPort.PARITY_EVEN);
}   catch (UnsupportedCommOperationException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}


BufferedReader is = null;  
PrintStream    os = null;

try {
is = new BufferedReader(new InputStreamReader(port.getInputStream()));
} catch (IOException e) {
System.err.println("Can't open input stream: write-only");
is = null;
}



try {
os = new PrintStream(port.getOutputStream(), true);

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}



// Actual data communication would happen here
os.print("08050080FF008D4B");


os.flush(); 


if (is != null)
try {
    is.close();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
if (os != null) os.close();
if (port != null) port.close();

} 

}

我怀疑是这一行有问题

os.print("08050080FF008D4B");

这是向微 Controller 发送命令的正确方法吗？

命令的含义

08- Controller ID,
05- MODBUS function for coil writing,
0080- Address of a register where value is to be written,
FF00- Boolean value,
8D4B- CRC checksum ,

Answer 1

您正在发送字符串 08050080FF008D4B。您可能希望将它们作为 bytes 而不是字符串值发送。您发送到设备的第一个字节是 0，即十六进制的 0x30。根据您的字符串和命令的含义，您可能希望第一个字节是 0x08。

所以，这样的事情可能会奏效(请注意，在不知道更多关于你正在使用的东西的情况下，我不能肯定地说):

byte[] bytes = new byte[]{ 0x08,0x05,0x00,(byte)0x80,(byte)0xFF,0x00,(byte)0x8D,(byte)0x4B };
//Later on in your code....
os.write( bytes );