從串口讀取雙倍

Question

我試圖從串行端口讀取雙精度。 我可以用String讀取它，但是當我將String解析為Double時，結果沒有任何意義，並且與String不同。

這是我的代碼：

public void serialEvent(SerialPortEvent event){
        switch(event.getEventType()) {

            case SerialPortEvent.DATA_AVAILABLE:
                byte[] readBuffer = new byte[8];
                try {
                    while (inputStream.available()>0) {
                     int numBytes = inputStream.read(readBuffer);
                     String peso = new String (readBuffer, 0, numBytes, "UTF-8");
                     System.out.print(new String (readBuffer, 0, numBytes, "UTF-8"));
                    //double d = ByteBuffer.wrap(readBuffer).order(ByteOrder.LITTLE_ENDIAN ).getDouble();
                    //System.out.print(d);
                     m_dWeightBuffer = Double.parseDouble(peso);
                     System.out.print(m_dWeightBuffer);
                     }
                     //System.out.print(new String (readBuffer, 0, numBytes, "UTF-8"));
                    } catch (IOException ex) {}
                break;

        } 
    }

但是現在，您知道如何將這個字符串轉換為Double嗎？

System.out.print(new String (readBuffer, 0, numBytes, "UTF-8")); 輸出： 000.250好

m_dWeightBuffer = Double.parseDouble(peso); System.out.print(m_dWeightBuffer); 輸出： 0.00.0250.0錯誤

System.out.println(new String (readBuffer, 0, numBytes, "UTF-8")); 輸出：

0 0 0 .250

Answer 1

前言

似乎服務器正在4個塊（可能是64位）上寫串行端口：

1. 0
2. 0
3. 0
4. .250

您正在讀取的最大緩沖區為64位（readBuffer.length * 8位），因此最后一個可能是：

0011111111010000000000000000000000000000000000000000000000000000

試試吧：

        String s = "0011111111010000000000000000000000000000000000000000000000000000"; 
        double d = Double.longBitsToDouble(Long.parseLong(s,2));
        System.out.println(d); //-> 0.25

至於現在沒錯 。

回答

可能您想在一個點上處理所有4個塊，因此您可以嘗試以下操作-當然，這很大程度上取決於我忽略的協議語義：

    public void serialEvent(SerialPortEvent event){
            switch(event.getEventType()) {

                case SerialPortEvent.DATA_AVAILABLE:
                    byte[] readBuffer = new byte[8];
                    String peso = "";
                    try {
                         while (inputStream.available()>0) {
                             int numBytes = inputStream.read(readBuffer);
                             peso += new String (readBuffer, 0, numBytes, "UTF-8");
                         }

                         m_dWeightBuffer = Double.parseDouble(peso);

                    } catch (IOException ex) {}
                    break;

            } 
    }

即，在讀取所有數據之后創建雙精度型。

Answer 2

嘗試這樣做：

 public void serialEvent(SerialPortEvent event){
            switch(event.getEventType()) {

                case SerialPortEvent.DATA_AVAILABLE:
                    byte[] readBuffer = new byte[8];


                    try {
                         while (inputStream.available()>0) {
                             int numBytes = inputStream.read(readBuffer);
                             peso += new String (readBuffer, 0, numBytes, "UTF-8").replaceAll("\\s+","").replaceAll("\\n", "").replaceAll("\\r", "");

                         }
                    } catch (IOException ex) {}

                    break;

            } 
    }

在此SerialEvent方法的外部初始化String peso。