Reading from serial port gives split up string

问题

I am using the JSSC class to receive a string from an Arduino Uno. The Arduino is connected to my computer via COM3. In the setup void on the Arduino, it sends a string to the java program saying that the Arduino is ready to read serial data. What happens is when the java program reads the serial port, it splits up the string from the Arduino onto multiple lines with spaces. I imagine it is that java program is printing the data when its received instead of waiting for the full string. How could I make it so that the program reads the string from the Arduino and saves it to a string and then prints it to console.

Java:

package jtac;

import jssc.*;

public class JTAC {

    public static SerialPort serialPort = new SerialPort("COM3");
    public static PortReader portreader = new PortReader(serialPort);
    public static boolean ready = false;

    public static void main(String[] args) {
        try {
            serialPort.openPort();//Open serial port
            //Thread.sleep(2000);
            serialPort.setParams(SerialPort.BAUDRATE_9600, 
                                 SerialPort.DATABITS_8,
                                 SerialPort.STOPBITS_1,
                                 SerialPort.PARITY_NONE);//Set params. Also you can set params by this string: serialPort.setParams(9600, 8, 1, 0);
            serialPort.setFlowControlMode(SerialPort.FLOWCONTROL_NONE);
            serialPort.addEventListener(portreader, SerialPort.MASK_RXCHAR);
            while(!ready) {} //Wait for Arduino to fire up
        }
        catch (SerialPortException ex) {
            System.out.println(ex);
        }   

    }

}
class PortReader implements SerialPortEventListener {

    SerialPort serialPort;
    public PortReader(SerialPort serialPort) {
        this.serialPort = serialPort;
    }

    @Override
    public void serialEvent(SerialPortEvent event) {
        if (event.isRXCHAR() && event.getEventValue() > 0) {
            try {
                String receivedData = serialPort.readString(event.getEventValue());
                System.out.println(receivedData);
                if(receivedData == "Arduino Ready") JTAC.ready = true;

            } catch (SerialPortException ex) {
                System.out.println("Error in receiving string from COM-port: " + ex);
            }
        }
    }
}

Arduino:

String input;

void setup() {
  Serial.begin(9600);
  Serial.print("Arduino Ready");
}

void loop() {

}

This is what the console outputs:

      Ard
uino
 Rea
dy

The spaces in front of Ard couldn't be copied from the console output. Is there a way I could make this all on one line? I might need to receive data from the Arduino again in the future as well. Thanks.

回答1:

Use Start and End Markers like "#Arduino Ready$"

Where "#" denotes starting and "$" denotes ending of string you interested. then you can use them to process the received bytes and store them based on the markers.

Check this awesome tutorial in the forum.

I might be completely wrong with the code [i'm a complete noob in java], but I think you can understand the overall idea.

Serial Event Method should be look like this

if (event.isRXCHAR() && event.getEventValue() > 0) {
    try {
        char receivedData = serialPort.read(event.getEventValue());
        if (recvData) === '#' {
            this.readString = 1
        }else if(recvData === '$'){
            this.readString = 0
        }

        if(this.readString == 1){
            this.recvStringData.append(receivedData)
            System.out.println(this.recvStringData);
        }

        if(this.recvStringData == "Arduino Ready") JTAC.ready = true;

    } catch (SerialPortException ex) {
        System.out.println("Error in receiving string from COM-port: " + ex);
    }
}

And Arduino code will be

void setup(){
   Serial.begin(9600);
   while(!Serial);
}

void loop(){
    Serial.println("#Hi There$");
}

来源：https://stackoverflow.com/questions/54921049/reading-from-serial-port-gives-split-up-string

标签

java

arduino

jssc