How to combine Java plot code and Java serial code to read Arduino sensor value?

Question

UPDATE: The code I am using can be found here: https://dl.dropbox.com/u/2108381/MyArduinoPlot.java I hope this helps to understand my challenge. Thanks in advance for your time.

I would like to read sensor values from an Arduino and chart them using the Java library JFreeChart.

I found some code on the internet (see below) and now, I would like to combine the code for plotting a dynamic line chart and the code for reading in the Arduino values. Both codes do work separately, but I got stuck in combining them both.

The code for plotting a dynamic line chart is from here (plots random data): http://dirtyhandsphp.blogspot.in/2012/07/how-to-draw-dynamic-line-or-timeseries.html

The code to read in Arduino values in Java is from here: http://arduino.cc/playground/Interfacing/Java

I assume (newbie in Java, though) that the relevant part is here:

/**
 * Handle an event on the serial port. Read the data and print it.
 */
public synchronized void serialEvent(SerialPortEvent oEvent) {
    if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
        try {
            int available = input.available();
            byte chunk[] = new byte[available];
            input.read(chunk, 0, available);

            // Displayed results are codepage dependent
            System.out.print(new String(chunk));

//              the code I tried

//              String MyValue = new String(chunk);
//              Double Value = Double.valueOf(MyValue); 

        } catch (Exception e) {
            System.err.println(e.toString());
        }
    }
    // Ignore all the other eventTypes, but you should consider the other ones.
}

and here:

public void actionPerformed(final ActionEvent e) {


//      Original Code

    final double factor = 0.9 + 0.2*Math.random();
    this.lastValue = this.lastValue * factor;

    final Millisecond now = new Millisecond();
    this.series.add(new Millisecond(), this.lastValue);

    System.out.println("Current Time in Milliseconds = " + now.toString()+", Current Value : "+this.lastValue);

//        my code
//        this.series.add(new Millisecond(), Value);


}

How can I make the public synchronized void serialEvent return the sensor value and how can I add it to the this.series.add part?

I am a newbie in Java.

Any direct help or linkage to other websites/posts is greatly appreciated. Thanks for your time.

Answer 1

In this example, a javax.swing.Timer periodically adds a new value to the dataset in the timer's ActionListener. You'll want to do it from outside. Here's an outline of how to proceed:

1. Move dataset and newData up to become instance variables:

   DynamicTimeSeriesCollection dataset;
   float[] newData = new float[1];
   

2. Add a method that appends your data to the chart's dataset:

   public synchronized void addData(byte[] chunk) {
       for (int i = 0; i < chunk.length; i++) {
           newData[0] = chunk[i];
           dataset.advanceTime();
           dataset.appendData(newData);
       }
   }
   

3. Invoke the method from serialEvent():

   demo.addChunk(chunk);