read data from rs-485 using java jssc

Question

I have weight indicator device that sends data using rs-485 protocol,

I am connecting it to computer using USB (serial to usb converter). using program (serial comm tester) i can read data correctly from it and it works fine. now I am trying to read this data using java using JSSC library and this is my code

public class Test2 {

    /**
     * @param args the command line arguments
     */
    static SerialPort serialPort;

    public static void main(String[] args) {
        serialPort = new SerialPort("COM9");
        try {
            serialPort.openPort();//Open port
            serialPort.setParams(SerialPort.BAUDRATE_115200,
                            SerialPort.DATABITS_8,
                             SerialPort.STOPBITS_1,
                             SerialPort.PARITY_NONE);//Set params
            int mask = SerialPort.MASK_RXCHAR + SerialPort.MASK_CTS + SerialPort.MASK_DSR;//Prepare mask
            serialPort.setEventsMask(mask);//Set mask
            serialPort.addEventListener(new SerialPortReader());//Add SerialPortEventListener
        } catch (SerialPortException ex) {
            System.out.println(ex);
        }
    }

    public static class SerialPortReader implements SerialPortEventListener {

        String buffer = "";
        private void onMessage() {
                // constructing message  
                System.out.println("RECEIVED MESSAGE: " + buffer);
                buffer = "";
        }

        @Override
        public void serialEvent(SerialPortEvent event) {
            if (event.isRXCHAR() && event.getEventValue() > 0) {
                try {
                    String b = serialPort.readString(event.getEventType());
                    System.out.println("event:"+b);
                    if (b.equals("\n") ) {
                        onMessage();
                    } else {
                        buffer += b;
                    }
                } catch (SerialPortException ex) {
                    System.out.println("Error in receiving string from COM-port: " + ex);
                }
            }
        }
    }

}

this is what data should look like and the option used in "serial comm tester" i should receive " 50.46 KG NT " serial comm tester output

but in java I can not read it correctly, any help please? java output

note that after multiple values sends java program shows some character from perivous data !!

kunif kunif · Accepted Answer · 2020-09-11T05:52:47

You're simply using the wrong function for the readString() parameter.
You should use getEventValue() instead of getEventType().

wrong:

String b = serialPort.readString(event.getEventType());

correct:

String b = serialPort.readString(event.getEventValue());

read data from rs-485 using java jssc

1 Answers