ESP32 i2s internal DAC output is not working in 2.0.4 and IDF 4.4.1

[ifrew]

I can confirm this is still broken in Arduino 2.0.4, IDF 4.4.1

Here is the sketch I used. If I change from internal DAC to PDM it works although really noisy.

// Arduino Zero / Feather M0 I2S audio tone generation example.
// Author: Tony DiCola
//
// Connect an I2S DAC or amp (like the UDA1334A) to the Arduino Zero
// and play back simple sine, sawtooth, triangle, and square waves.
// Makes your Zero sound like a NES!
//
// NOTE: The I2S signal generated by the Zero does NOT have a MCLK /
// master clock signal.  You must use an I2S receiver that can operate
// without a MCLK signal (like the UDA1334A).
//
// For an Arduino Zero / Feather M0 connect it to you I2S hardware as follows:
// - Digital 0 -> I2S LRCLK / FS (left/right / frame select clock)
// - Digital 1 -> I2S BCLK / SCLK (bit / serial clock)
// - Digital 9 -> I2S DIN / SD (data output)
// - Ground
//
// Released under a MIT license: https://opensource.org/licenses/MIT

//modified for M5Stack Gray Core

#include <M5Stack.h>
#include <driver/i2s.h>

#define SPEAKER_I2S_NUMBER I2S_NUM_0

#define SAMPLERATE_HZ 44100  // The sample rate of the audio.  Higher sample rates have better fidelity,
                             // but these tones are so simple it won't make a difference.  44.1khz is
                             // standard CD quality sound.

#define AMPLITUDE     ((1<<31)-1)   // Set the amplitude of generated waveforms.  This controls how loud
                             // the signals are, and can be any value from 0 to 2**31 - 1.  Start with
                             // a low value to prevent damaging speakers!

#define WAV_SIZE      256    // The size of each generated waveform.  The larger the size the higher
                             // quality the signal.  A size of 256 is more than enough for these simple
                             // waveforms.

// Define the frequency of music notes (from http://www.phy.mtu.edu/~suits/notefreqs.html):
#define C4_HZ      261.63
#define D4_HZ      293.66
#define E4_HZ      329.63
#define F4_HZ      349.23
#define G4_HZ      392.00
#define A4_HZ      440.00
#define B4_HZ      493.88

// Define a C-major scale to play all the notes up and down.
float scale[] = { C4_HZ, D4_HZ, E4_HZ, F4_HZ, G4_HZ, A4_HZ, B4_HZ, A4_HZ, G4_HZ, F4_HZ, E4_HZ, D4_HZ, C4_HZ };

// Store basic waveforms in memory.
int32_t sine[WAV_SIZE]     = {0};
int32_t sawtooth[WAV_SIZE] = {0};
int32_t triangle[WAV_SIZE] = {0};
int32_t square[WAV_SIZE]   = {0};
size_t writeSize;

// Create I2S audio transmitter object.
//Adafruit_ZeroI2S i2s;

#define Serial Serial

void generateSine(int32_t amplitude, int32_t* buffer, uint16_t length) {
  // Generate a sine wave signal with the provided amplitude and store it in
  // the provided buffer of size length.
  for (int i=0; i<length; ++i) {
    buffer[i] = int32_t(float(amplitude)*sin(2.0*PI*(1.0/length)*i));
  }
}
void generateSawtooth(int32_t amplitude, int32_t* buffer, uint16_t length) {
  // Generate a sawtooth signal that goes from -amplitude/2 to amplitude/2
  // and store it in the provided buffer of size length.
  float delta = float(amplitude)/float(length);
  for (int i=0; i<length; ++i) {
    buffer[i] = -(amplitude/2)+delta*i;
  }
}

void generateTriangle(int32_t amplitude, int32_t* buffer, uint16_t length) {
  // Generate a triangle wave signal with the provided amplitude and store it in
  // the provided buffer of size length.
  float delta = float(amplitude)/float(length);
  for (int i=0; i<length/2; ++i) {
    buffer[i] = -(amplitude/2)+delta*i;
  }
    for (int i=length/2; i<length; ++i) {
    buffer[i] = (amplitude/2)-delta*(i-length/2);
  }
}

void generateSquare(int32_t amplitude, int32_t* buffer, uint16_t length) {
  // Generate a square wave signal with the provided amplitude and store it in
  // the provided buffer of size length.
  for (int i=0; i<length/2; ++i) {
    buffer[i] = -(amplitude/2);
  }
    for (int i=length/2; i<length; ++i) {
    buffer[i] = (amplitude/2);
  }
}

void playWave(int32_t* buffer, uint16_t length, float frequency, float seconds) {
  // Play back the provided waveform buffer for the specified
  // amount of seconds.
  // First calculate how many samples need to play back to run
  // for the desired amount of seconds.
  uint32_t iterations = seconds*SAMPLERATE_HZ;
  // Then calculate the 'speed' at which we move through the wave
  // buffer based on the frequency of the tone being played.
  float delta = (frequency*length)/float(SAMPLERATE_HZ);
  // Now loop through all the samples and play them, calculating the
  // position within the wave buffer for each moment in time.
  for (uint32_t i=0; i<iterations; ++i) {
    uint16_t pos = uint32_t(i*delta) % length;
    int32_t sample = buffer[pos];
    // Duplicate the sample so it's sent to both the left and right channel.
    // It appears the order is right channel, left channel if you want to write
    // stereo sound.
    i2s_write(SPEAKER_I2S_NUMBER, &sample, sizeof(sample), &writeSize, portMAX_DELAY);
  }
}

void setup() {
  // Configure serial port.
  Serial.begin(115200);

  Serial.printf("ESP-IDF Version %d.%d.%d \r\n", ESP_IDF_VERSION_MAJOR, ESP_IDF_VERSION_MINOR, ESP_IDF_VERSION_PATCH);
  Serial.printf("Ardunio Version %d.%d.%d \r\n", ESP_ARDUINO_VERSION_MAJOR, ESP_ARDUINO_VERSION_MINOR, ESP_ARDUINO_VERSION_PATCH);

  M5.begin(true, true, true, true);

  Serial.println("Audio Tone Generator");

  // Initialize the I2S transmitter.
  esp_err_t err = ESP_OK;

  //i2s_driver_uninstall(SPEAKER_I2S_NUMBER);
  i2s_config_t i2s_config = {
      .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX | I2S_MODE_DAC_BUILT_IN),
      .sample_rate = SAMPLERATE_HZ ,
      .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT, // is fixed at 12bit, stereo, MSB
      .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
      .communication_format = I2S_COMM_FORMAT_I2S,
      .intr_alloc_flags = 0,
      .dma_buf_count = 2,
      .dma_buf_len = 256
  };

  i2s_config.use_apll = false;
  i2s_config.tx_desc_auto_clear = true;

  err += i2s_driver_install(SPEAKER_I2S_NUMBER, &i2s_config, 0, NULL);
  i2s_pin_config_t tx_pin_config;

  tx_pin_config.mck_io_num = 0;
  tx_pin_config.bck_io_num = 12;
  tx_pin_config.ws_io_num = 13;
  tx_pin_config.data_out_num = 15;
  tx_pin_config.data_in_num = 34;

  err += i2s_set_pin(SPEAKER_I2S_NUMBER, NULL);

  err += i2s_set_clk(SPEAKER_I2S_NUMBER, SAMPLERATE_HZ, I2S_BITS_PER_SAMPLE_16BIT, I2S_CHANNEL_MONO);

  // Generate waveforms.
  generateSine(AMPLITUDE, sine, WAV_SIZE);
  generateSawtooth(AMPLITUDE, sawtooth, WAV_SIZE);
  generateTriangle(AMPLITUDE, triangle, WAV_SIZE);
  generateSquare(AMPLITUDE, square, WAV_SIZE);
}

void loop() {
  Serial.println("Sine wave");
  for (int i=0; i<sizeof(scale)/sizeof(float); ++i) {
    // Play the note for a quarter of a second.
    playWave(sine, WAV_SIZE, scale[i], 0.25);
    // Pause for a tenth of a second between notes.
    delay(100);
  }
  Serial.println("Sawtooth wave");
  for (int i=0; i<sizeof(scale)/sizeof(float); ++i) {
    // Play the note for a quarter of a second.
    playWave(sawtooth, WAV_SIZE, scale[i], 0.25);
    // Pause for a tenth of a second between notes.
    delay(100);
  }
  Serial.println("Triangle wave");
  for (int i=0; i<sizeof(scale)/sizeof(float); ++i) {
    // Play the note for a quarter of a second.
    playWave(triangle, WAV_SIZE, scale[i], 0.25);
    // Pause for a tenth of a second between notes.
    delay(100);
  }
  Serial.println("Square wave");
  for (int i=0; i<sizeof(scale)/sizeof(float); ++i) {
    // Play the note for a quarter of a second.
    playWave(square, WAV_SIZE, scale[i], 1.0);
    // Pause for a tenth of a second between notes.
    //delay(1);
    delay(100);
  }
}

Originally posted by @ifrew in https://github.com/espressif/arduino-esp32/issues/5938#issuecomment-1152838615

[SuGlider]

@ifrew

Internal DAC sample is 8 bits. https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/i2s.html#configuring-i2s-to-use-internal-dac-for-analog-output

The wave samples generated in the presented sketch are based on 32 bits amplitude, thus the DAC will output ZEROs most of the time.

Try out this example that generates a sine wave form using internal DAC. It'd be very easy to adapt it to an Arduino Sketch: https://github.com/infrasonicaudio/esp32-i2s-synth-example/blob/main/main/i2s_example_main.c

There is no issue with Arduino or IDF...

[SuGlider]

This is the Arduino sketch, converted from the previous IDF APP that outputs a Sine Stereo in the DAC:

/* I2S Synthesis example
    This example code will output a sine wave of arbitrary frequency WAVE_FREQ_HZ
    (default 235 Hz) at 44100 Hz sample rate to the internal 8-bit DAC channels of
    the ESP32.
    This example code is in the Public Domain (or CC0 licensed, at your option.)
    Unless required by applicable law or agreed to in writing, this
    software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
    CONDITIONS OF ANY KIND, either express or implied.
*/

#include "driver/i2s.h"

#define SAMPLE_RATE     (44100)
#define DMA_BUF_LEN     (32)
#define DMA_NUM_BUF     (2)
#define I2S_NUM         ((i2s_port_t)(0))
#define WAVE_FREQ_HZ    (235.0f)
#define TWOPI           (6.28318531f)
#define PHASE_INC       (TWOPI * WAVE_FREQ_HZ / SAMPLE_RATE)

// Accumulated phase
static float p = 0.0f;

// Output buffer (2ch interleaved)
static uint16_t out_buf[DMA_BUF_LEN * 2];

// Fill the output buffer and write to I2S DMA
static void write_buffer()
{
    float samp = 0.0f;
    size_t bytes_written;

    for (int i=0; i < DMA_BUF_LEN; i++) {
        // Scale sine sample to 0-1 for internal DAC
        // (can't output negative voltage)
        samp = (sinf(p) + 1.0f) * 0.5f;

        // Increment and wrap phase
        p += PHASE_INC;
        if (p >= TWOPI)
            p -= TWOPI;

        // Scale to 8-bit integer range
        samp *= 255.0f;

        // Shift to MSB of 16-bit int for internal DAC
        out_buf[i*2] = out_buf[i*2+1] = (uint16_t)samp << 8;
    }

    // Write with max delay. We want to push buffers as fast as we
    // can into DMA memory. If DMA memory isn't transmitted yet this
    // will yield the task until the interrupt fires when DMA buffer has 
    // space again. If we aren't keeping up with the real-time deadline,
    // audio will glitch and the task will completely consume the CPU,
    // not allowing any task switching interrupts to be processed.
    i2s_write(I2S_NUM, out_buf, sizeof(out_buf), &bytes_written, portMAX_DELAY);
}

void setup(void)
{
    i2s_config_t i2s_config = {
        .mode = (i2s_mode_t) (I2S_MODE_MASTER | I2S_MODE_TX | I2S_MODE_DAC_BUILT_IN),
        .sample_rate = SAMPLE_RATE,
        .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
        .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
        .communication_format = I2S_COMM_FORMAT_STAND_MSB,
        .intr_alloc_flags = ESP_INTR_FLAG_LEVEL2,
        .dma_buf_count = DMA_NUM_BUF,
        .dma_buf_len = DMA_BUF_LEN,
        .use_apll = false
    };

    i2s_driver_install(I2S_NUM, &i2s_config, 0, NULL);

    i2s_set_pin(I2S_NUM, NULL); // Internal DAC
}

void loop()
{
        write_buffer();
}

[SuGlider]

The sketch above outputs 8bits + 8bits (stereo with 16bits per sample) in the pins 25 and 26 (DAC Pins) of the ESP32. There is no output to the I2S pins...

[ifrew]

Interesting. Looking at the implementation of i2s, it can take up to 32 bits. I was sure the underlying implementation would take care of handling the transfer to the 8 bits DAC. However, You were right about the sketch being wrong. Looking at the sine wave example you gave from IDF, when I changed the communication format to I2S_COMM_FORMAT_STAND_MSB from I2S_COMM_FORMAT_I2S the sketch I provide with 32bit Amplitude works now.

I will close this out. Thanks for the info!