无法发送消息，从我的串行端口连接设备在 java 中读取响应

Question

我有一个连接到 mi PC 和 RS 232 的秤，还有一个 USB 到 RS 232 转换器（如果有人知道的话，ATEN USB 到串行桥接器）。

我只想立即从比例中获得 wheight，但我需要发送一个 ASCII 'W'。

When the host requests weight data by sending an uppercase W, the scale will respond with the weight data or a status byte if the scale is in motion or an invalid state.

来自秤的手册。

所以我做了那个代码：

import gnu.io.*;
import java.io.*;
import java.util.Enumeration;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;


public class PruebaMia implements SerialPortEventListener{

    static CommPortIdentifier portId;
    static Enumeration portList;

    InputStream inputStream;
    SerialPort serialPort;
    Thread readThread;

    String output = "W/r/t";


public static void main(String[] args) throws IOException, UnsupportedCommOperationException {
    PruebaMia pm = new PruebaMia();
    pm.FlashWriteMethod();
}

public void FlashWriteMethod() throws IOException, UnsupportedCommOperationException {
    portList = CommPortIdentifier.getPortIdentifiers();
        while (portList.hasMoreElements()) {
            portId = (CommPortIdentifier) portList.nextElement();
            if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
                if (portId.getName().equals("COM4")) {
                try {
                    serialPort = (SerialPort) portId.open("SimpleWriteApp", 2000);
                    } catch (PortInUseException e) {}
                serialPort.setSerialPortParams(9600, SerialPort.DATABITS_7, SerialPort.STOPBITS_1, SerialPort.PARITY_EVEN);

                BufferedReader is = null;  // for demo purposes only. A stream would be more typical.
                PrintStream    os = null;
                try {
            serialPort.addEventListener(this);
            } catch (TooManyListenersException e) {
                System.out.println("Tooo many Listener exception");}

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

                os = new PrintStream(serialPort.getOutputStream(), true);

                os.print("W");
                os.print("\r\n");


                // Read the response
                String response = is.readLine();
                OutputStream mOutputToPort = serialPort.getOutputStream();
                inputStream = serialPort.getInputStream();
                System.out.println(" Input Stream... " + inputStream);

                BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(mOutputToPort));
                bw.write(output);
                bw.flush();

                inputStream = serialPort.getInputStream();
                System.out.println(" Input Stream... " + inputStream);
                }
             }
        }
}

 public void serialEvent(SerialPortEvent event){
        switch(event.getEventType()) {
            case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
                outputBufferEmpty(event);
                break;

            case SerialPortEvent.DATA_AVAILABLE:
                dataAvailable(event);
                break;
        }
    }

    protected void outputBufferEmpty(SerialPortEvent event) {
    }

    protected void dataAvailable(SerialPortEvent event) {
        System.out.println("Data available event received");
//        try{
//            while (inputStream.available() > 0){
//                int numBytes = inputStream.read(readBuffer);}
//            
//        vBuffer += new String(readBuffer);
//        System.out.print(new String(readBuffer));
//        
//        }catch (IOException e){
//            System.out.println(e);}
//    }
    }

}

我认为我没有很好地将“W”发送到秤，所以它抛出了一个异常：

Exception in thread "main" java.io.IOException: Underlying input stream returned zero bytes

我在做什么坏事？

编辑：

我的秤是奥豪斯 RV 系列。

Answer 1

大卫，那个秤有 4 种类型的协议（原因是仅重量模式（WO））。

我建议您将 Elpsa 用于 WO 模式。 从手册：

The spanish competitor Epelsa has developed a protocol for the communication between checkout scales [ only-weight scales ] and POS [ or PC ] which has become kind of standard in the spanish market for this type of connections, thereof our interest that our only-weight scales become compatible.

您可以使用 9600 波特、8 个数据位、1 个停止位、偶数位。 您可以更改此设置，但使用默认比例配置这些是最好的。 （如果你想使用其他人，你应该改变规模配置）

要使用此协议，请使用此框：

所以要接收重量，你应该发送一个 '$' 字符