PCM.h

/*
 * speaker_pcm
 *
 * Plays 8-bit PCM audio on pin 11 using pulse-width modulation (PWM).
 * For Arduino with Atmega168 at 16 MHz.
 *
 * Uses two timers. The first changes the sample value 8000 times a second.
 * The second holds pin 11 high for 0-255 ticks out of a 256-tick cycle,
 * depending on sample value. The second timer repeats 62500 times per second
 * (16000000 / 256), much faster than the playback rate (8000 Hz), so
 * it almost sounds halfway decent, just really quiet on a PC speaker.
 *
 * Takes over Timer 1 (16-bit) for the 8000 Hz timer. This breaks PWM
 * (analogWrite()) for Arduino pins 9 and 10. Takes Timer 2 (8-bit)
 * for the pulse width modulation, breaking PWM for pins 11 & 3.
 *
 * References:
 *     http://www.uchobby.com/index.php/2007/11/11/arduino-sound-part-1/
 *     http://www.atmel.com/dyn/resources/prod_documents/doc2542.pdf
 *     http://www.evilmadscientist.com/article.php/avrdac
 *     http://gonium.net/md/2006/12/27/i-will-think-before-i-code/
 *     http://fly.cc.fer.hr/GDM/articles/sndmus/speaker2.html
 *     http://www.gamedev.net/reference/articles/article442.asp
 *
 * Michael Smith <michael@hurts.ca>
 */

/*
 * The audio data needs to be unsigned, 8-bit, 8000 Hz, and small enough
 * to fit in flash. 10000-13000 samples is about the limit.
 *
 * sounddata.h should look like this:
 *     const int sounddata_length=10000;
 *     const unsigned char sounddata_data[] PROGMEM = { ..... };
 *
 * You can use wav2c from GBA CSS:
 *     http://thieumsweb.free.fr/english/gbacss.html
 * Then add "PROGMEM" in the right place. I hacked it up to dump the samples
 * as unsigned rather than signed, but it shouldn't matter.
 *
 * http://musicthing.blogspot.com/2005/05/tiny-music-makers-pt-4-mac-startup.html
 * mplayer -ao pcm macstartup.mp3
 * sox audiodump.wav -v 1.32 -c 1 -r 8000 -u -1 macstartup-8000.wav
 * sox macstartup-8000.wav macstartup-cut.wav trim 0 10000s
 * wav2c macstartup-cut.wav sounddata.h sounddata
 *
 * (starfox) nb. under sox 12.18 (distributed in CentOS 5), i needed to run
 * the following command to convert my wav file to the appropriate format:
 * sox audiodump.wav -c 1 -r 8000 -u -b macstartup-8000.wav
 */

#include <avr/pgmspace.h>

#ifdef __cplusplus
extern "C" {
#endif

void startPlayback(unsigned char const *data, int length);
void stopPlayback();

#ifdef __cplusplus
}
#endif