Beeper.java

//    HomeAutomation software to accompany the book 
//    'Practical Arduino + Android Projects for the Evil Genius'
//    Copyright (C) 2011. Simon Monk
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    (at your option) any later version.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU General Public License for more details.
//
//    You should have received a copy of the GNU General Public License
//    along with this program.  If not, see <http://www.gnu.org/licenses/>.

package com.simonmonk.home;

import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;

public class Beeper {

	private final static int SAMPLE_RATE = 16000;
	
    private final static int ONE_DURATION = 32;
    private final static int ZERO_DURATION = 8;
    private final static int BIT_DURATION = 64;
    private final static int DURATION = BIT_DURATION * 32;
    private final static float f = 1000.0f;

    
	private short[] buffer = null;
    
	public synchronized void beep(int word)
	{
		AudioTrack at;
		int bufsizbytes = DURATION * SAMPLE_RATE / 1000;
		int bufsizsamps = bufsizbytes / 2;
		buffer = new short[bufsizsamps];
		fillbuf(word, bufsizsamps);
		try 
		{
			at = new AudioTrack(AudioManager.STREAM_MUSIC, SAMPLE_RATE,
					AudioFormat.CHANNEL_CONFIGURATION_MONO,
					AudioFormat.ENCODING_PCM_16BIT, bufsizbytes,
					AudioTrack.MODE_STATIC);
			at.setStereoVolume(1.0f, 1.0f);
			at.write(buffer, 0, bufsizsamps);
			at.play();
			Thread.sleep(2000);
		} 
		catch (Exception e) 
		{
			e.printStackTrace();
		}

	}


	void fillbuf(int word, int bufsizsamps) 
	{
		double omega, t;
		double dt = 1.0 / SAMPLE_RATE; 
		t = 0.0;
		omega = (float) (2.0 * Math.PI * f);
		for (int i = 0; i < bufsizsamps; i++) 
		{
			if (toneRequired(t, word))
			{
				buffer[i] = (short) (32000.0 * Math.sin(omega * t));
			}
			else
			{
				buffer[i] = 0;
			}
			t += dt;
		}
	}
	
	boolean toneRequired(double t, long word)
	{
		int ms = (int) (t * 1000);
		int bitIndex = ms / BIT_DURATION;
		int bit = (int) ((word >> (15 - bitIndex)) & 1);
		int msWithinBit = ms - (bitIndex * BIT_DURATION);
		
		if (bit == 1 && msWithinBit < ONE_DURATION)
		{
			return true;
		}
		if (bit == 0 && msWithinBit < ZERO_DURATION)
		{
			return true;
		}
		return false;
	}
	
}