Serial Port Reading with Processing, cannot find the string

Question

I am trying to read serial port from Processing. In that purpose I am trying basic hello world example. I write Hello world! from Arduino and try to catch it with Processing. Here are the codes:

Here is the code for Arduino Uno:

void setup() 
{
  //initialize serial communications at a 9600 baud rate
  Serial.begin(9600);
}

void loop()
{
  //send 'Hello, world!' over the serial port
  Serial.println("Hello, world!");
  //wait 100 milliseconds so we don't drive ourselves crazy
  delay(100);
}

Here is the code for Processing:

import processing.serial.*;

Serial myPort;  // Create object from Serial class

String val;     // Data received from the serial port
String check     = "Hello, world!";
String portName  = Serial.list()[1]; //COM4



void setup() {
  myPort = new Serial(this, portName, 9600);
  println("Starting Serial Read Operation");
}

void draw()
{

  if ( myPort.available() > 0) {  // If data is available,


    val = myPort.readStringUntil('\n');


    println(val);
    if (val != null && val.equals("Hello, world!") == true) {

      println("Found the starting Point");
    }
  }
}

I cannot catch the check string.

Output of the Processing :

null
Hello, world!

null
Hello, world!

null
Hello, world!

Hello, world!

According to the output, I can successfully read the serial port. (However there are many nulls, I don't know why.) But I cannot catch the specified string.

Do you have an idea what the problem can be?

Regards

Chris A Chris A · Accepted Answer · 2015-07-24T06:17:31

The Arduino sends \r\n when using println.

When you compare, it fails as you are comparing "Hello, world!\r" with "Hello, world!".

You can solve this by using Serial.print() and manually adding an \n to your strings or sending a Serial.write('\n'); after your text (repetition can be replaced with a helper function).

Serial Port Reading with Processing, cannot find the string

1 Answers