Basic Wav recorder

EchoCharlie · Apr 22, 2025

Hello everyone,
I'm experimenting with the sound module and Teensy 4.0

I would like to be able to record and playback mono Wav files, with 3 buttons: Rec, Stop, Play.
However there's something wrong with the header as I'm not able to open the wav files.

Find below the code. Any help would be much appreciated.

Code:

// 
//
// Requires the audio shield:
//   http://www.pjrc.com/store/teensy3_audio.html
//
// Three pushbuttons need to be connected:
//   Record Button: pin 0 to GND
//   Stop Button:   pin 1 to GND
//   Play Button:   pin 2 to GND
//
// This example code is in the public domain.

#include <Bounce.h>
#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
//#include <SD_t3.h>
#include <SerialFlash.h>



// GUItool: begin automatically generated code
AudioInputI2S            i2s2;           //xy=169,221
AudioPlaySdWav           playSdWav1;     //xy=186,419
AudioRecordQueue         queue1;         //xy=365,236
AudioOutputI2S           i2s1;           //xy=414,422
AudioConnection          patchCord1(i2s2, 0, queue1, 0);
AudioConnection          patchCord2(playSdWav1, 0, i2s1, 0);
AudioControlSGTL5000     sgtl5000_1;     //xy=265,212
// GUItool: end automatically generated code


//write wav
unsigned long ChunkSize = 0L;
unsigned long Subchunk1Size = 16;
unsigned int AudioFormat = 1;
unsigned int numChannels = 1;
unsigned long sampleRate = 44100;
unsigned int bitsPerSample = 16;
unsigned long byteRate = sampleRate*numChannels*(bitsPerSample/8);// samplerate x channels x (bitspersample / 8)
unsigned int blockAlign = numChannels*bitsPerSample/8;
unsigned long Subchunk2Size = 0L;
unsigned long recByteSaved = 0L;
unsigned long NumSamples = 0L;
byte byte1, byte2, byte3, byte4;

// For a stereo recording version, see this forum thread:
// https://forum.pjrc.com/threads/46150?p=158388&viewfull=1#post158388

// A much more advanced sound recording and data logging project:
// https://github.com/WMXZ-EU/microSoundRecorder
// https://github.com/WMXZ-EU/microSoundRecorder/wiki/Hardware-setup
// https://forum.pjrc.com/threads/52175?p=185386&viewfull=1#post185386

// Bounce objects to easily and reliably read the buttons
Bounce buttonRecord = Bounce(0, 8);
Bounce buttonStop =   Bounce(1, 8);  // 8 = 8 ms debounce time
Bounce buttonPlay =   Bounce(2, 8);


// which input on the audio shield will be used?
const int myInput = AUDIO_INPUT_LINEIN;
//const int myInput = AUDIO_INPUT_MIC;


// Use these with the Teensy Audio Shield
#define SDCARD_CS_PIN    10
#define SDCARD_MOSI_PIN  7   // Teensy 4 ignores this, uses pin 11
#define SDCARD_SCK_PIN   14  // Teensy 4 ignores this, uses pin 13

// Use these with the Teensy 3.5 & 3.6 & 4.1 SD card
//#define SDCARD_CS_PIN    BUILTIN_SDCARD
//#define SDCARD_MOSI_PIN  11  // not actually used
//#define SDCARD_SCK_PIN   13  // not actually used

// Use these for the SD+Wiz820 or other adaptors
//#define SDCARD_CS_PIN    4
//#define SDCARD_MOSI_PIN  11
//#define SDCARD_SCK_PIN   13


// Remember which mode we're doing
int mode = 0;  // 0=stopped, 1=recording, 2=playing

// The file where data is recorded
File frec;

void setup() {
  // Configure the pushbutton pins
  pinMode(0, INPUT_PULLUP);
  pinMode(1, INPUT_PULLUP);
  pinMode(2, INPUT_PULLUP);

  // Audio connections require memory, and the record queue
  // uses this memory to buffer incoming audio.
  AudioMemory(60);

  // Enable the audio shield, select input, and enable output
  sgtl5000_1.enable();
  sgtl5000_1.inputSelect(myInput);
  sgtl5000_1.volume(0.5);

  // Initialize the SD card
  SPI.setMOSI(SDCARD_MOSI_PIN);
  SPI.setSCK(SDCARD_SCK_PIN);
  if (!(SD.begin(SDCARD_CS_PIN))) {
    // stop here if no SD card, but print a message
    while (1) {
      Serial.println("Unable to access the SD card");
      delay(500);
    }
  }
}


void loop() {
  // First, read the buttons
  buttonRecord.update();
  buttonStop.update();
  buttonPlay.update();

  // Respond to button presses
  if (buttonRecord.fallingEdge()) {
    Serial.println("Record Button Press");
    if (mode == 2) stopPlaying();
    if (mode == 0) startRecording();
  }
  if (buttonStop.fallingEdge()) {
    Serial.println("Stop Button Press");
    if (mode == 1) stopRecording();
    if (mode == 2) stopPlaying();
  }
  if (buttonPlay.fallingEdge()) {
    Serial.println("Play Button Press");
    if (mode == 1) stopRecording();
    if (mode == 0) startPlaying();
  }

  // If we're playing or recording, carry on...
  if (mode == 1) {
    continueRecording();
  }
  if (mode == 2) {
    continuePlaying();
  }

  // when using a microphone, continuously adjust gain
  if (myInput == AUDIO_INPUT_MIC) adjustMicLevel();
}


void startRecording() {
  Serial.println("startRecording");

  char filename[20];
  int fileNumber = 1;

  // Generate a new filename that doesn't exist yet
  do {
    sprintf(filename, "REC%03d.WAV", fileNumber);
    fileNumber++;
  } while (SD.exists(filename) && fileNumber < 1000); // Limit to 999 files

  // Open the file for writing
  frec = SD.open(filename, FILE_WRITE);
  if (frec) {
    Serial.print("Recording to: ");
    Serial.println(filename);
    queue1.begin();
    mode = 1;
    recByteSaved = 0L;
  } else {
    Serial.println("Failed to create file!");
  }

}

void continueRecording() {
  if (queue1.available() >= 2) {
    byte buffer[512];
    // Fetch 2 blocks from the audio library and copy
    // into a 512 byte buffer.  The Arduino SD library
    // is most efficient when full 512 byte sector size
    // writes are used.
    memcpy(buffer, queue1.readBuffer(), 256);
    queue1.freeBuffer();
    memcpy(buffer+256, queue1.readBuffer(), 256);
    queue1.freeBuffer();
    // write all 512 bytes to the SD card
    //elapsedMicros usec = 0;
    frec.write(buffer, 512);
    // Uncomment these lines to see how long SD writes
    // are taking.  A pair of audio blocks arrives every
    // 5802 microseconds, so hopefully most of the writes
    // take well under 5802 us.  Some will take more, as
    // the SD library also must write to the FAT tables
    // and the SD card controller manages media erase and
    // wear leveling.  The queue1 object can buffer
    // approximately 301700 us of audio, to allow time
    // for occasional high SD card latency, as long as
    // the average write time is under 5802 us.
    //Serial.print("SD write, us=");
    //Serial.println(usec);
  }
}

void stopRecording() {
  Serial.println("stopRecording");
  queue1.end();
  if (mode == 1) {
    while (queue1.available() > 0) {
      frec.write((byte*)queue1.readBuffer(), 256);
      queue1.freeBuffer();
    }
    frec.close();
  }
  mode = 0;
}


void startPlaying() {
  Serial.println("startPlaying");
  playSdWav1.play("REC%03d.WAV");
  mode = 2;
}

void continuePlaying() {
  if (!playSdWav1.isPlaying()) {
    playSdWav1.stop();
    mode = 0;
  }
}

void stopPlaying() {
  Serial.println("stopPlaying");
  if (mode == 2) playSdWav1.stop();
  mode = 0;
}

void adjustMicLevel() {
  // TODO: read the peak1 object and adjust sgtl5000_1.micGain()
  // if anyone gets this working, please submit a github pull request :-)
}


void writeOutHeader() { // update WAV header with final filesize/datasize


//  NumSamples = (recByteSaved*8)/bitsPerSample/numChannels;
//  Subchunk2Size = NumSamples*numChannels*bitsPerSample/8; // number of samples x number of channels x number of bytes per sample
  Subchunk2Size = recByteSaved;
  ChunkSize = Subchunk2Size + 36;
  frec.seek(0);
  frec.write("RIFF");
  byte1 = ChunkSize & 0xff;
  byte2 = (ChunkSize >> 8) & 0xff;
  byte3 = (ChunkSize >> 16) & 0xff;
  byte4 = (ChunkSize >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  frec.write("WAVE");
  frec.write("fmt ");
  byte1 = Subchunk1Size & 0xff;
  byte2 = (Subchunk1Size >> 8) & 0xff;
  byte3 = (Subchunk1Size >> 16) & 0xff;
  byte4 = (Subchunk1Size >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  byte1 = AudioFormat & 0xff;
  byte2 = (AudioFormat >> 8) & 0xff;
  frec.write(byte1);  frec.write(byte2);
  byte1 = numChannels & 0xff;
  byte2 = (numChannels >> 8) & 0xff;
  frec.write(byte1);  frec.write(byte2);
  byte1 = sampleRate & 0xff;
  byte2 = (sampleRate >> 8) & 0xff;
  byte3 = (sampleRate >> 16) & 0xff;
  byte4 = (sampleRate >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  byte1 = byteRate & 0xff;
  byte2 = (byteRate >> 8) & 0xff;
  byte3 = (byteRate >> 16) & 0xff;
  byte4 = (byteRate >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  byte1 = blockAlign & 0xff;
  byte2 = (blockAlign >> 8) & 0xff;
  frec.write(byte1);  frec.write(byte2);
  byte1 = bitsPerSample & 0xff;
  byte2 = (bitsPerSample >> 8) & 0xff;
  frec.write(byte1);  frec.write(byte2);
  frec.write("data");
  byte1 = Subchunk2Size & 0xff;
  byte2 = (Subchunk2Size >> 8) & 0xff;
  byte3 = (Subchunk2Size >> 16) & 0xff;
  byte4 = (Subchunk2Size >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  frec.close();
  Serial.println("header written");
  Serial.print("Subchunk2: ");
  Serial.println(Subchunk2Size);
}

h4yn0nnym0u5e · Apr 22, 2025

You (or someone...) seem to have grafted together a couple of example sketches and come up with an unholy mess. You'd probably be better off finding a single example which is closer to your aim. Off the top of my head I can see three issues:

writeOutHeader() is defined but never called, so you have a raw audio file, not a WAV
recByteSaved is not added to during recording, so the header would say there's no audio data in the file

I recognise the writeOutHeader() code, and it calculates incorrect values: it needs to be

C++:

  Subchunk2Size = recByteSaved - 21; // we're about to overwrite this much audio data
  ChunkSize = Subchunk2Size + 34;  // correct this calculation

That last bug isn't fatal, many playback applications work anyway.

EchoCharlie · Apr 22, 2025

Hello @h4yn0nnym0u5e and thanks a lot for your hint.
It worked!

EchoCharlie · Apr 23, 2025

Hi again,
now the module records as expected but I'm unable to playback the files directly from the sound module SD reader.
I wonder if the sequential naming I added messes up with playSdWav.
The serial monitor says:
11:09:45.007 -> Play Button Press
11:09:45.007 -> startPlaying

...but nothing happens when I press the Stop button.

Here's the code:

Code:

// Record sound as Wav to a SD card, and play it back.
// Three pushbuttons need to be connected:
//   Record Button: pin 0 to GND
//   Stop Button:   pin 1 to GND
//   Play Button:   pin 2 to GND
//

#include <Bounce.h>
#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>


// GUItool: begin automatically generated code
AudioInputI2S            i2s2;           //xy=169,221
AudioPlaySdWav           playSdWav1;     //xy=186,419
AudioRecordQueue         queue1;         //xy=365,236
AudioOutputI2S           i2s1;           //xy=414,422
AudioConnection          patchCord1(i2s2, 0, queue1, 0);
AudioConnection          patchCord2(playSdWav1, 0, i2s1, 0);
AudioConnection          patchCord3(playSdWav1, 1, i2s1, 1);
AudioControlSGTL5000     sgtl5000_1;     //xy=300,502
// GUItool: end automatically generated code



//write wav
unsigned long ChunkSize = 0L;
unsigned long Subchunk1Size = 16;
unsigned int AudioFormat = 1;
unsigned int numChannels = 1;
unsigned long sampleRate = 44100;
unsigned int bitsPerSample = 16;
unsigned long byteRate = sampleRate*numChannels*(bitsPerSample/8);// samplerate x channels x (bitspersample / 8)
unsigned int blockAlign = numChannels*bitsPerSample/8;
unsigned long Subchunk2Size = 0L;
unsigned long recByteSaved = 0L;
unsigned long NumSamples = 0L;
byte byte1, byte2, byte3, byte4;

// For a stereo recording version, see this forum thread:
// https://forum.pjrc.com/threads/46150?p=158388&viewfull=1#post158388

// A much more advanced sound recording and data logging project:
// https://github.com/WMXZ-EU/microSoundRecorder
// https://github.com/WMXZ-EU/microSoundRecorder/wiki/Hardware-setup
// https://forum.pjrc.com/threads/52175?p=185386&viewfull=1#post185386

// Bounce objects to easily and reliably read the buttons
Bounce buttonRecord = Bounce(0, 8);
Bounce buttonStop =   Bounce(1, 8);  // 8 = 8 ms debounce time
Bounce buttonPlay =   Bounce(2, 8);


// which input on the audio shield will be used?
const int myInput = AUDIO_INPUT_LINEIN;
//const int myInput = AUDIO_INPUT_MIC;


// Use these with the Teensy Audio Shield
#define SDCARD_CS_PIN    10
#define SDCARD_MOSI_PIN  7   // Teensy 4 ignores this, uses pin 11
#define SDCARD_SCK_PIN   14  // Teensy 4 ignores this, uses pin 13

// Use these with the Teensy 3.5 & 3.6 & 4.1 SD card
//#define SDCARD_CS_PIN    BUILTIN_SDCARD
//#define SDCARD_MOSI_PIN  11  // not actually used
//#define SDCARD_SCK_PIN   13  // not actually used

// Use these for the SD+Wiz820 or other adaptors
//#define SDCARD_CS_PIN    4
//#define SDCARD_MOSI_PIN  11
//#define SDCARD_SCK_PIN   13


// Remember which mode we're doing
int mode = 0;  // 0=stopped, 1=recording, 2=playing

// The file where data is recorded
File frec;

void setup() {
  // Configure the pushbutton pins
  pinMode(0, INPUT_PULLUP);
  pinMode(1, INPUT_PULLUP);
  pinMode(2, INPUT_PULLUP);

  // Audio connections require memory, and the record queue
  // uses this memory to buffer incoming audio.
  AudioMemory(60);

  // Enable the audio shield, select input, and enable output
  sgtl5000_1.enable();
  sgtl5000_1.inputSelect(myInput);
  sgtl5000_1.volume(0);

  // Initialize the SD card
  SPI.setMOSI(SDCARD_MOSI_PIN);
  SPI.setSCK(SDCARD_SCK_PIN);
  if (!(SD.begin(SDCARD_CS_PIN))) {
    // stop here if no SD card, but print a message
    while (1) {
      Serial.println("Unable to access the SD card");
      delay(500);
    }
  }
}


void loop() {
  // First, read the buttons
  buttonRecord.update();
  buttonStop.update();
  buttonPlay.update();

  // Respond to button presses
  if (buttonRecord.fallingEdge()) {
    Serial.println("Record Button Press");
    if (mode == 2) stopPlaying();
    if (mode == 0) startRecording();
  }
  if (buttonStop.fallingEdge()) {
    Serial.println("Stop Button Press");
    if (mode == 1) stopRecording();
    if (mode == 2) stopPlaying();
  }
  if (buttonPlay.fallingEdge()) {
    Serial.println("Play Button Press");
    if (mode == 1) stopRecording();
    if (mode == 0) startPlaying();
  }

  // If we're playing or recording, carry on...
  if (mode == 1) {
    continueRecording();
  }
  if (mode == 2) {
    continuePlaying();
  }

  // when using a microphone, continuously adjust gain
  //if (myInput == AUDIO_INPUT_MIC) adjustMicLevel();
}


void startRecording() {
  Serial.println("startRecording");

  char filename[20];
  int fileNumber = 1;

  // Generate a new filename that doesn't exist yet
  do {
    sprintf(filename, "REC%03d.WAV", fileNumber);
    fileNumber++;
  } while (SD.exists(filename) && fileNumber < 1000); // Limit to 999 files

  // Open the file for writing
  frec = SD.open(filename, FILE_WRITE);
  if (frec) {
    Serial.print("Recording to: ");
    Serial.println(filename);
    queue1.begin();
    mode = 1;
    recByteSaved = 0L;
  } else {
    Serial.println("Failed to create file!");
  }

}

void continueRecording() {
 
  if (queue1.available() >= 2) {
    byte buffer[512];
    memcpy(buffer, queue1.readBuffer(), 256);
    queue1.freeBuffer();
    memcpy(buffer + 256, queue1.readBuffer(), 256);
    queue1.freeBuffer();
    // write all 512 bytes to the SD card
    frec.write(buffer, 512);
    recByteSaved += 512;
//    elapsedMicros usec = 0;
//    Serial.print("SD write, us=");
//    Serial.println(usec);
  }
}

void stopRecording() {
  Serial.println("stopRecording");
  queue1.end();
  if (mode == 1) {
    while (queue1.available() > 0) {
      frec.write((byte*)queue1.readBuffer(), 256);
      queue1.freeBuffer();
    }
    writeOutHeader();
    frec.close();
  }
  mode = 0;
}


void startPlaying() {
  Serial.println("startPlaying");
  playSdWav1.play("REC%03d.WAV");
  mode = 2;
}

void continuePlaying() {
  if (!playSdWav1.isPlaying()) {
    playSdWav1.stop();
    mode = 0;
  }
}

void stopPlaying() {
  Serial.println("stopPlaying");
  if (mode == 2) playSdWav1.stop();
  mode = 0;
}

void adjustMicLevel() {
  // TODO: read the peak1 object and adjust sgtl5000_1.micGain()
  // if anyone gets this working, please submit a github pull request :-)
}




void writeOutHeader() { // update WAV header with final filesize/datasize


//  NumSamples = (recByteSaved*8)/bitsPerSample/numChannels;
//  Subchunk2Size = NumSamples*numChannels*bitsPerSample/8; // number of samples x number of channels x number of bytes per sample
  Subchunk2Size = recByteSaved -21;
  ChunkSize = Subchunk2Size + 34;
  frec.seek(0);
  frec.write("RIFF");
  byte1 = ChunkSize & 0xff;
  byte2 = (ChunkSize >> 8) & 0xff;
  byte3 = (ChunkSize >> 16) & 0xff;
  byte4 = (ChunkSize >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  frec.write("WAVE");
  frec.write("fmt ");
  byte1 = Subchunk1Size & 0xff;
  byte2 = (Subchunk1Size >> 8) & 0xff;
  byte3 = (Subchunk1Size >> 16) & 0xff;
  byte4 = (Subchunk1Size >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  byte1 = AudioFormat & 0xff;
  byte2 = (AudioFormat >> 8) & 0xff;
  frec.write(byte1);  frec.write(byte2);
  byte1 = numChannels & 0xff;
  byte2 = (numChannels >> 8) & 0xff;
  frec.write(byte1);  frec.write(byte2);
  byte1 = sampleRate & 0xff;
  byte2 = (sampleRate >> 8) & 0xff;
  byte3 = (sampleRate >> 16) & 0xff;
  byte4 = (sampleRate >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  byte1 = byteRate & 0xff;
  byte2 = (byteRate >> 8) & 0xff;
  byte3 = (byteRate >> 16) & 0xff;
  byte4 = (byteRate >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  byte1 = blockAlign & 0xff;
  byte2 = (blockAlign >> 8) & 0xff;
  frec.write(byte1);  frec.write(byte2);
  byte1 = bitsPerSample & 0xff;
  byte2 = (bitsPerSample >> 8) & 0xff;
  frec.write(byte1);  frec.write(byte2);
  frec.write("data");
  byte1 = Subchunk2Size & 0xff;
  byte2 = (Subchunk2Size >> 8) & 0xff;
  byte3 = (Subchunk2Size >> 16) & 0xff;
  byte4 = (Subchunk2Size >> 24) & 0xff; 
  frec.write(byte1);  frec.write(byte2);  frec.write(byte3);  frec.write(byte4);
  frec.close();
  Serial.println("header written");
  Serial.print("Subchunk2: ");
  Serial.println(Subchunk2Size);
}

h4yn0nnym0u5e · Apr 23, 2025

Here's a major issue:

C++:

playSdWav1.play("REC%03d.WAV");

Your code never generates a file with that name! You need to write the code that re-creates the complete filename from the number. The example doesn't bother to check the return value from the call so you don't get told it failed.

There's also a hidden gotcha. AudioPlaySdWav objects don't set isPlaying() true for a few milliseconds after play() is called (bad design), so there's an extremely good chance that continuePlaying() will decide the playback has stopped when in fact it hasn't even started. If it called stopPlaying() then you'd get a message, but it calls playSdWav1.stop() and doesn't emit its own "File ended" message.

Basic Wav recorder

EchoCharlie

Member

h4yn0nnym0u5e

Well-known member

EchoCharlie

Member

EchoCharlie

Member

h4yn0nnym0u5e

Well-known member