[mareczek]

Poniższy kod powoduje jednorazowe odtworzenie zapisanej melodii.
Co i gdzie powinienem wpisać aby uzyskać zapętlenie odtwarzania melodii bez użycia delay

Kod:

/*
* 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>
*/

#include <stdint.h>
#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/pgmspace.h>

#define SAMPLE_RATE 8000

/*
* 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 "sounddata.h"

int ledPin = 13;
int speakerPin = 11; // Can be either 3 or 11, two PWM outputs connected to Timer 2
volatile uint16_t sample;
byte lastSample;


void stopPlayback()
{
   // Disable playback per-sample interrupt.
   TIMSK1 &= ~_BV(OCIE1A);

   // Disable the per-sample timer completely.
   TCCR1B &= ~_BV(CS10);

   // Disable the PWM timer.
   TCCR2B &= ~_BV(CS10);

   digitalWrite(speakerPin, LOW);
}

// This is called at 8000 Hz to load the next sample.
ISR(TIMER1_COMPA_vect) {
   if (sample >= sounddata_length) {
       if (sample == sounddata_length + lastSample) {
           stopPlayback();
       }
       else {
           if(speakerPin==11){
               // Ramp down to zero to reduce the click at the end of playback.
               OCR2A = sounddata_length + lastSample - sample;
           } else {
               OCR2B = sounddata_length + lastSample - sample;                
           }
       }
   }
   else {
       if(speakerPin==11){
           OCR2A = pgm_read_byte(&sounddata_data[sample]);
       } else {
           OCR2B = pgm_read_byte(&sounddata_data[sample]);            
       }
   }

   ++sample;
}

void startPlayback()
{
   pinMode(speakerPin, OUTPUT);

   // Set up Timer 2 to do pulse width modulation on the speaker
   // pin.

   // Use internal clock (datasheet p.160)
   ASSR &= ~(_BV(EXCLK) | _BV(AS2));

   // Set fast PWM mode  (p.157)
   TCCR2A |= _BV(WGM21) | _BV(WGM20);
   TCCR2B &= ~_BV(WGM22);

   if(speakerPin==11){
       // Do non-inverting PWM on pin OC2A (p.155)
       // On the Arduino this is pin 11.
       TCCR2A = (TCCR2A | _BV(COM2A1)) & ~_BV(COM2A0);
       TCCR2A &= ~(_BV(COM2B1) | _BV(COM2B0));
       // No prescaler (p.158)
       TCCR2B = (TCCR2B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);

       // Set initial pulse width to the first sample.
       OCR2A = pgm_read_byte(&sounddata_data[0]);
   } else {
       // Do non-inverting PWM on pin OC2B (p.155)
       // On the Arduino this is pin 3.
       TCCR2A = (TCCR2A | _BV(COM2B1)) & ~_BV(COM2B0);
       TCCR2A &= ~(_BV(COM2A1) | _BV(COM2A0));
       // No prescaler (p.158)
       TCCR2B = (TCCR2B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);

       // Set initial pulse width to the first sample.
       OCR2B = pgm_read_byte(&sounddata_data[0]);
   }





   // Set up Timer 1 to send a sample every interrupt.

   cli();

   // Set CTC mode (Clear Timer on Compare Match) (p.133)
   // Have to set OCR1A *after*, otherwise it gets reset to 0!
   TCCR1B = (TCCR1B & ~_BV(WGM13)) | _BV(WGM12);
   TCCR1A = TCCR1A & ~(_BV(WGM11) | _BV(WGM10));

   // No prescaler (p.134)
   TCCR1B = (TCCR1B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);

   // Set the compare register (OCR1A).
   // OCR1A is a 16-bit register, so we have to do this with
   // interrupts disabled to be safe.
   OCR1A = F_CPU / SAMPLE_RATE;    // 16e6 / 8000 = 2000

   // Enable interrupt when TCNT1 == OCR1A (p.136)
   TIMSK1 |= _BV(OCIE1A);

   lastSample = pgm_read_byte(&sounddata_data[sounddata_length-1]);
   sample = 0;
   sei();
}


void setup()
{
   pinMode(ledPin, OUTPUT);
   digitalWrite(ledPin, HIGH);
   startPlayback();
}

void loop()
{
   while (true);
}