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Flash sound

Play sound from flash memory in IC

Flash memory

IC/Board Flash memory(Program Memory)
UNO(328P) 32 KB
ATtiny412 4 KB
ATtiny1614 16 KB
ATtiny3216 32 KB

Download mp3 sample

ref. Orenge free sounds

dog.mp3

Convert mp3 to hex text file

ref. WAVまたはMP3ファイルを再生する

Useage

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% ffmpeg -y -i input.mp3 -acodec pcm_u8 -f u8 -ac 1 -ar 8000 output.pcm
% xxd -i output.pcm > output.h
ffmpeg parameters 
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 -y  :Overwrite output files without asking
 -i  :input/file/path
 -acodec :Set the audio codec (pcm_u8 = PCM unsigned 8-bit)
 -f  :Format (u8 = PCM unsigned 8-bit)
 -ac :Number of audio channels (1 = monaural)
 -ar :Audio sampling frequency (8000 [Hz])

xxd (hexdamp) parameters 

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-i  : C include file style output
>   :Redirection of output

Convert mp3 to hexdamp text file 

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% ls
 dog.mp3 //293KB

// Shorten large mp3 to 1 sec(seek start position 0[s] to duration 1[s])
% ffmpeg -ss 0 -i dog.mp3 -t 1 dog_1sec.mp3

// Convert to .pcm with 4000Hz
% ffmpeg -y -i dog_1sec.mp3 -acodec pcm_u8 -f u8 -ac 1 -ar 4000 dog.pcm

// Write to hexdamp file as .h for arduino
% xxd -i dog.pcm > dog.h

% ls
 dog.mp3       // 293KB
 dog_1sec.mp3  // 17KB
 dog.pcm       //  4KB
 dog.h         // 25KB

Arduino Sketch

ref Arduinoで鉢植えをしゃべらせる

dog.h

Open dog.h and add const and PROGMEM in 1st line

Before: unsigned char dog_pcm[] = { 

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unsigned char dog_pcm[] = {
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  ....
  0x80, 0x80, 0x80, 0x80
};
unsigned int dog_pcm_len = 4000;
After: const unsigned char dog_pcm[] PROGMEM = {

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const unsigned char dog_pcm[] PROGMEM= {
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  ....
  0x80, 0x80, 0x80, 0x80
};
unsigned int dog_pcm_len = 4000;

flash_sound.ino

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#include "dog.h"

void setup() {
  pinMode(3, OUTPUT); //speaker pin
  TCCR2A = _BV(COM2B1) | _BV(WGM21) | _BV(WGM20);
  TCCR2B = _BV(CS20);
  play();
}

void play() {
  for (int i = 0; i < dog_pcm_len; i++) {
    OCR2B = pgm_read_byte_near(&dog_pcm[i]);
    delayMicroseconds(250); //1000000uSec/4000Hz
  }
}

void loop() {
}

Save both in one folder

download flash_sound.ino|dog.h

Connection

Speaker (+) to Pin3
Speaker (-) to GND

Hint

To louder, use NPN bipolar transistor such as 2SC1815.
Connection:
- Base to Pin3
- 5V to Speaker (+)
- Emitter to Speaker (-)
- Collector to GND

Video

video link

Last update: August 19, 2021