Modbus java slave app

文章實現 Modbus slave app , 用 serial rtu 傳輸， 代碼只實現監聽功能(本人測試可行)， 要實現寫功能，可研究一下代碼中 updateProcessImage 方法。完整代碼(先閱讀 README.md ) ：http://git.oschina.net/jlpostbox/demo-modbus

public static void main(String[] args) throws Exception {

        String commPortId = "COM2";
        int baudRate = 9600;
        int flowControlIn = 0;
        int flowControlOut = 0;
        int dataBits = 8;
        int stopBits = 1;
        int parity = 0;

        SerialPortWrapperImpl wrapper = new SerialPortWrapperImpl(commPortId, baudRate, flowControlIn, flowControlOut, dataBits, stopBits, parity);
        ModbusFactory modbusFactory = new ModbusFactory();

        final ModbusSlaveSet listener = modbusFactory.createRtuSlave(wrapper);

        // Add a few slave process images to the listener.
        listener.addProcessImage(getModscanProcessImage(1));
 
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    listener.start();
                }
                catch (ModbusInitException e) {
                    e.printStackTrace();
                }
            }
        }).start();

    }static class BasicProcessImageListener implements ProcessImageListener {
        @Override
        public void holdingRegisterWrite(int offset, short oldValue, short newValue) {

            System.out.println("HR at " + offset + " was set from " + oldValue + " to " + newValue);
        }
    }

    static BasicProcessImage getModscanProcessImage(int slaveId) {
        //建立10個可讀寫的數字類型，與主機對應
        BasicProcessImage processImage = new BasicProcessImage(slaveId);
        processImage.setInvalidAddressValue(Short.MIN_VALUE);
        processImage.setHoldingRegister(0,(short) 8);
        processImage.setHoldingRegister(1,(short) 8);
        processImage.setHoldingRegister(2,(short) 8);
        processImage.setHoldingRegister(3,(short) 8);
        processImage.setHoldingRegister(4,(short) 8);
        processImage.setHoldingRegister(5,(short) 8);
        processImage.setHoldingRegister(6,(short) 8);
        processImage.setHoldingRegister(7,(short) 8);
        processImage.setHoldingRegister(8,(short) 8);
        processImage.setHoldingRegister(9,(short) 8);
        // Add an image listener.
        processImage.addListener(new BasicProcessImageListener());
        return processImage;
    }

 開發中遇到一個問題，short的取值是 -32768~32767 ， 而對方發過來的是 0~65535 ， 這樣當發過來是32757~65535，java這邊收到的是 -32768~ -1 ， 咱們就得利用Java位運算符，完成Unsigned轉換

public int getUnsignedByte (byte data){      //將data字節型數據轉換爲0~255 (0xFF 即BYTE)。
　　return data&0x0FF;
}
public int getUnsignedByte (short data){      //將data字節型數據轉換爲0~65535 (0xFFFF 即 WORD)。
　　return data&0x0FFFF;
}       
public long getUnsignedIntt (int data){     //將int數據轉換爲0~4294967295 (0xFFFFFFFF即DWORD)。
　　return data&0x0FFFFFFFFl;
}