/**
 * RSSI Viewer - view RSSI values of 802.15.4 channels
 * ---------------------------------------------------
 * Note: run the rssi-scanner on a Sky or sentilla node connected to USB
 * then start with
 * make login | java ViewRSSI
 *
 * Created: Fri Apr 24 00:40:01 2009, Joakim Eriksson
 *
 * @author Joakim Eriksson, SICS
 * @version 1.0
 */
import javax.swing.*;
import java.awt.*;
import java.io.*;
public class ViewRSSI extends JPanel {

  private int[] rssi = new int[80];
  private int[] rssiMax = new int[80];

  /* this is the max value of the RSSI from the cc2420 */
  private static final int RSSI_MAX_VALUE = 200;

  public ViewRSSI() {
  }

  public void paint(Graphics g) {
    int h = getHeight();
    int w = getWidth();
    double factor = (h - 20.0) / RSSI_MAX_VALUE;
    double sSpacing = (w - 15 ) / 80.0;
    int sWidth = (int) (sSpacing - 1);
    if (sWidth == 0) sWidth = 1;

    g.setColor(Color.white);
    g.fillRect(0, 0, w, h);

    g.setColor(Color.gray);
    double xpos = 10;
    for (int i = 0, n = rssi.length; i < n; i++) {
      int rssi = (int) (rssiMax[i] * factor);
      g.fillRect((int) xpos, h - 20 - rssi,
		 sWidth, rssi + 1);
      xpos += sSpacing;
    }

    g.setColor(Color.black);
    xpos = 10;
    for (int i = 0, n = rssi.length; i < n; i++) {
      int rssiVal = (int) (rssi[i] * factor);
      g.fillRect((int) xpos, h - 20 - rssiVal,
		 sWidth, rssiVal + 1);
      xpos += sSpacing;
    }
  }

  private void handleInput() throws IOException {
    BufferedReader reader =
      new BufferedReader(new InputStreamReader(System.in));
    while(true) {
      String line = reader.readLine();
      if (line.startsWith("RSSI:")) {
	try {
	  String[] parts = line.substring(5).split(" ");
	  for (int i = 0, n = parts.length; i < n; i++) {
	    rssi[i] = 3 * Integer.parseInt(parts[i]);
	    if (rssi[i] > rssiMax[i]) rssiMax[i] = rssi[i];
	    else if (rssiMax[i] > 0) rssiMax[i]--;
	  }
	} catch (Exception e) {
	  /* report but do not fail... */
	  e.printStackTrace();
	}
	repaint();
      }
    }
  }

  public static void main(String[] args) throws IOException {
    JFrame win = new JFrame("RSSI Viewer");
    ViewRSSI panel;
    win.setBounds(10, 10, 300, 300);
    win.getContentPane().add(panel = new ViewRSSI());
    win.setVisible(true);
    win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    panel.handleInput();
  }
}

/**
 * RSSI Viewer - view RSSI values of 802.15.4 channels
 * ---------------------------------------------------
 * Note: run the rssi-scanner on a Sky or sentilla node connected to USB
 * then start with
 * make login | java ViewRSSI
 *
 * Created: Fri Apr 24 00:40:01 2009, Joakim Eriksson
 *
 * @author Joakim Eriksson, SICS
 * @version 1.0
 */
import javax.swing.*;
import java.awt.*;
import java.io.*;


public class ViewRSSI extends JPanel {
	
	private int[] rssi = new int[80];
	private int[] rssiMax = new int[80];
	
	/* this is the max value of the RSSI from the cc2420 */
	private static final int RSSI_MAX_VALUE = 200;
	
	public ViewRSSI() {
	}
	
	public void paint(Graphics g) {
		int h = getHeight();
		int w = getWidth();
		double factor = (h - 20.0) / RSSI_MAX_VALUE;
		double sSpacing = (w - 15) / 80.0;
		int sWidth = (int) (sSpacing - 1);
		if (sWidth == 0)
			sWidth = 1;
		
		g.setColor(Color.white);
		g.fillRect(0, 0, w, h);
		
		g.setColor(Color.gray);
		double xpos = 10;
		for (int i = 0, n = rssi.length; i < n; i++) {
			int rssi = (int) (rssiMax[i] * factor);
			g.fillRect((int) xpos, h - 20 - rssi, sWidth, rssi + 1);
			xpos += sSpacing;
		}
		
		g.setColor(Color.black);
		xpos = 10;
		for (int i = 0, n = rssi.length; i < n; i++) {
			int rssiVal = (int) (rssi[i] * factor);
			g.fillRect((int) xpos, h - 20 - rssiVal, sWidth, rssiVal + 1);
			xpos += sSpacing;
		}
	}
	
	private void handleInput() throws IOException {
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
		while (true) {
			String line = reader.readLine();
			if (line.startsWith("RSSI:")) {
				try {
					String[] parts = line.substring(5).split(" ");
					for (int i = 0, n = parts.length; i < n; i++) {
						rssi[i] = 3 * Integer.parseInt(parts[i]);
						if (rssi[i] > rssiMax[i])
							rssiMax[i] = rssi[i];
						else if (rssiMax[i] > 0)
							rssiMax[i]--;
					}
				} catch (Exception e) {
					/* report but do not fail... */
					e.printStackTrace();
				}
				repaint();
			}
		}
	}
	
	public static void main(String[] args) throws IOException {
		JFrame win = new JFrame("RSSI Viewer");
		ViewRSSI panel;
		win.setBounds(10, 10, 300, 300);
		win.getContentPane().add(panel = new ViewRSSI());
		win.setVisible(true);
		win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		panel.handleInput();
	}
}

Fix indention of ViewRSSI.java