8bit 8khz, playback to different pin

Other Hardware Audio
1

im using a method similar to this
http://playground.arduino.cc/Code/PCMAudio

but it does not work with the motor shield (servo.h)
speaker is set to pin 11

speaker_out on pins 9 or 10 woudl be great (servo ports on motor header)
or 2 and 13 could work since they are not connected to the motor shield controls

main program

#include <PCM.h>

const unsigned char gun[] PROGMEM = {
// gun
130, 126, 136, 135 // snip

};
const unsigned char cannon[] PROGMEM = {
// cannon
117, 126, 140, 151  // snip
};



void setup()
{

}

void loop()
{

    startPlayback(gun, sizeof(gun));
   delay(236); 
   delay(3000); 
    startPlayback(cannon, sizeof(cannon));
   delay(2000); 
   delay(3000); 

}

PCM.c

/*
 * 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

#if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif

#include "PCM.h"

/*
 * 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
 */

int speakerPin = 11;
unsigned char const *sounddata_data=0;
int sounddata_length=0;
volatile uint16_t sample;
byte lastSample;

// 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 {
      // Ramp down to zero to reduce the click at the end of playback.
      OCR2A = sounddata_length + lastSample - sample;
    }
  }
  else {
    OCR2A = pgm_read_byte(&sounddata_data[sample]);
  }
  
  ++sample;
}

void startPlayback(unsigned char const *data, int length)
{
  sounddata_data = data;
  sounddata_length = length;

  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);
  
  // 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]);
  
  
  // 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 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);
}

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

thanks in advance

2

on
pcm.c
i changed

int speakerPin = 11;

to any other pin and it does not work

3

is there a way to direct write the pwm auidio out the motor shield?
speaker + to ground or +/- on one of the motor terminals

4

speaker_out on pins 9 or 10 woudl be great

The sound output works through using two timers. Each timer can only generate a PWM signal on one of two pins. This is fixed in the hardware design of the chip. Timer 2 uses pins 3 and 11, so the only option to using pin 11 for an audio output is to use pin 3. This will involve changing the code that sets up the timer. Just changing the value of the variable speakerPin will have no effect as the code isn't actually written to take note of this value during the setting up of the timers. In that respect the code is not very good.

Note that servo control will also require these two timers and you can't use them both at the same time for different purposes.

5

thanks,
thats what i was afraid of

ill use that wav code and use L298N dual H drivers for the motors on unused pins
set 1 side to LOW/ other to pwm value
2 pins per motor isnt as bad as 10 for the motor shield
i only need 3 motors (left/right tracks and turret), and the speaker