Read double from serial port

Question

Im trying to read a double from a serial port. I can read it in String, but when I parse the String to Double, the result makes no sense, and it's not the same from the String.

This is my code:

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;

        } 
    }

But now, you know how I can convert this string to Double?

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

m_dWeightBuffer = Double.parseDouble(peso); System.out.print(m_dWeightBuffer); Output: 0.00.0250.0 Bad

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

0 0 0 .250

Answer 1

Try doing this:

 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;

            } 
    }

Inicialize the String peso OUTSIDE of this SerialEvent method.

Answer 2

Foreword

It seems the server is writing on the serial port in 4 chunks, probably 64bits words:

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

You are reading with a max buffer of 64 bits (readBuffer.length * 8 bits), so the last could be:

0011111111010000000000000000000000000000000000000000000000000000

Try it:

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

As for now nothing is wrong.

Answer

Probably you are wanting to process all 4 chunks in a single point, so you could try the following - of course, much depends on the protocol's semantics which I ignore:

    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;

            } 
    }

That is, the double is created after all the data is read.