使用串行通信在微控制器上写入数据时出现问

时间:2013-02-17 03:07:35

标签: java com serial-port serial-communication modbus

我正在尝试使用串行通信向微控制器发送命令,我可以编译并运行以下代码而没有任何错误,但是值没有写入寄存器。我做错了什么?

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();

} 

}

我怀疑问题在于这一行

os.print("08050080FF008D4B");

这是向微控制器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 ,

1 个答案:

答案 0 :(得分:3)

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。您要发送到设备的第一个字节是0,其中十六进制为0x30。根据您的字符串和命令的含义,您可能希望第一个字节为0x08

所以,这样的事情可能会奏效(请注意,如果不知道你正在做什么,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 );