ESP8266 Community Forum

Posted: **Tue Jan 24, 2023 4:27 pm**

Hey guys, for a project we are making a synth that can play a sinewave or mix multiple (with button input for each sinewave) outputting sound with I2S via a small speaker

However whatever we do, we end up getting an overhead with our current method and the tones glitch out. Does anyone know how we can fix this or improve on this?

sine code:

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#ifndef SOUND_GENERATOR_H
#define SOUND_GENERATOR_H
#include <Arduino.h>

const double octive_base_freq = 110.0; // A2
const double d12_root_of_2 = pow(2.0,1.0/12);
double clacFreq(uint8 note) {octive_base_freq*pow(d12_root_of_2,note);}


#define PI2 6.283185307179586232


enum waveType {
    Sine,
    Square,
    Tri,
    Saw,
    Noise
};

// sine approx
double fsin(double x) {
    double t = x*0.15915;
    t = t - (int)t;
    if (t < 0.5) {
        return (-16.0 * t * t) + (8.0 * t);
    } else {
        return (16.0 * t * t) - (16.0 * t) - (8.0 * t) + 8.0;
    }
}

// faster sin approx
double ffsin(double x) {
    float t = x*0.15915f;
    t = t-(int)t;
    return 20.785f*t*(t-0.5f)*(t-1.0f);
}



double sineWave(double freq, double dTime) {
    return sin(freq*dTime*PI2);
}
double twoSineWaves(double freq, double dTime) {
    return (ffsin(freq*dTime*PI2)+ffsin(freq*4*dTime+0.1*PI2)+ffsin(freq*8*dTime+0.2*PI2))*0.33;
}
double squareWave(double freq, double dTime) {
    return sineWave(freq, dTime) > 0 ? 1 : -1;
}
double triangleWave(double freq, double dTime) {
    return asin(sin((freq*PI2)*dTime)) * 2.0/PI;
    
}


double osc(double freq, double dTime, int Type) {
    switch (Type)
    {
    case 0:
        /* code */
        break;
    
    default:
        break;
    }
}





#endif

main ino code:

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// Code was geschreven voor de ESP8266
#include <Arduino.h>
#include <ESP8266WiFi.h>
#include "src/SoundGenerator/sound_generator.h"
#include <Wire.h>

// IOs used for I2S. Not defined in i2s.h, unfortunately.
// Note these are internal GPIO numbers and not pins on an
// Arduino board. Users need to verify their particular wiring.
// Most of the pins are only used when i2s clock is enabled
// I2SO_DATA 3
// I2SO_BCK  15
// I2SO_WS   2
// I2SI_DATA 12
// I2SI_BCK  13
// I2SI_WS   14
#include <I2S.h>
#include <I2S_reg.h>

// i2s pins are
// I2SO_DATA 3(RX)  -> DIN 
// I2SO_BCK  15(D8) -> BCLK
// I2SO_WS   2(D4)  -> LRC

// playback vars
const uint32_t sample_rate = 32000;

#define SLAVE_ADDR 9
const char term = '\n';



void setup()
{
  system_update_cpu_freq(160);

  // turn off ESP8266 RF
  WiFi.forceSleepBegin(); 
  delay(1); 

  // start serial
  Serial.begin(115200);
  while (!Serial);

  // i2c
  Wire.begin(SLAVE_ADDR);

  // start i2s
  i2s_begin();
  i2s_set_rate(sample_rate);
  i2s_set_bits(16);

  Serial.println("Begin!");
}


inline int16_t double2int(double d)
{
    d += 6755399441055744.0;
    return reinterpret_cast<int16_t&>(d);
}


double volume = 0.1;
float offset = 0;
double dSample=0;

int16_t buffer[512];
int noteIndex=0;
int state=0;
double notemap[24] = {
  261.626,277.183,293.665,311.127,329.628,349.228,369.994,391.995,415.305,440.00,466.164,493.883,
  523.251,554.365,587.330,622.254,659.225,698.456,739.989,783.991,830.609,880.00,932.328,987.767};


void loop()
{
  if (Wire.available()>0) {
    String ms = Wire.readStringUntil(term);
    noteIndex = ms.substring(0,2).toInt();
    state = ms.substring(2,3).toInt();
  }


  // audio stuff
  for(int i=0;i<512;i++) {
    if (noteIndex<25) {
      dSample = sineWave(notemap[noteIndex], offset);
      buffer[i] = double2int(dSample*32767*volume);
      offset+=31.25*0.000001; 
      if (offset>1) {
        offset = offset-1;
      }    
    } else {
      buffer[i] = 0;
    }
  }
  
  for (int i=0; i<512;i++) {
    i2s_write_sample(buffer[i]);
  }  
 
}

ESP8266 Community Forum

Creating an mixing a sinewave with esp8266

Creating an mixing a sinewave with esp8266