STM to ESP

[pito]

Post #22 gives me the 4 channels as I need, now I need to regulate amplitude sine channel, whatever I do the amplitude is not changing.
This part of code

void generateWaveforms() {
  for (int i = 0; i < WAVEFORM_SAMPLES; i++) {
    // wave_data1[i] = (uint8_t)((255 * i) / WAVEFORM_SAMPLES);
    wave_data1[i] = (uint8_t)( (50 + cos(2 * 3.14159 * i / WAVEFORM_SAMPLES)));
    wave_data2[i] = (uint8_t)(127.5 * (1 + sin(2 * 3.14159 * i / WAVEFORM_SAMPLES)));
    // int dutyCycle = (int)(amp + amp * sin(stp * i)); // Calculate the duty cycle

  }
  for (int i = 0; i < WAVEFORM_SAMPLES; i++) {
    stereo_buffer[i * 2] = wave_data1[i];      // DAC1
    stereo_buffer[i * 2 + 1] = wave_data2[i];  // DAC2
  }
}
​

[pito]

So far I have 2 squares for synchronous detectors (0 deg and 90 deg), 1 one sin for coil balance and one sin for ground balance.
Sin waves need to be regulated in amplitude and phase = working on it.

void generateWaveforms() {
  //for (int i = 0; i < WAVEFORM_SAMPLES; i++)
  for (int i = 0; i < WAVEFORM_SAMPLES; i++)
  {
    wave_data1[i] = (uint8_t)(128 * (1 + sin(stp * i)));  //127.5; // Half of the max value (255/2)  //\+++++++++++++++++++++++++
    //wave_data2[i] = (uint8_t)(100 * (1 + sin(stp * i)));
      wave_data2[i] = (uint8_t)(100 * (1 + cos(stp * i)));                                                                   //  +++++++++++++++++++++++  
    // int dutyCycle = (int)(amp + amp * sin(stp * i)); //
  }

  for (int i = 0; i < WAVEFORM_SAMPLES; i++) {
    stereo_buffer[i * 2] = wave_data1[i];      // DAC1
    stereo_buffer[i * 2 + 1] = wave_data2[i];  // DAC2
  }
}
​

[pito]

Those two line should produce 2 sin waves shifted by 90 deg but they are giving no phase shifted sine.

   wave_data1[i] = (uint8_t)(128 * (1 + sin(stp * i)));  //127.5; // Half of the max value (255/2)  //\+++++++++++++++++++++++++

      wave_data2[i] = (uint8_t)(100 * (1 + cos(stp * i)));                                                                   //  +++++++++++++++++++++++  ​

This line produces a sine wave on both DACs (DAC 1 and DAC 2).

 wave_data2[i] = (uint8_t)(127.5 * (1 + sin(2 * 3.14159 * i / WAVEFORM_SAMPLES)));

This line does not produce a sine wave on both DACs (DAC 1 and DAC 2).

wave_data1[i] = (uint8_t)(127.5 * (1 + sin(2 * 3.14159 * i / WAVEFORM_SAMPLES)));//

[ivconic]

Harder to follow because I'm not in a position to do the same thing as you.
In that case it's fun to ask the AI.
Too bad I can't copy the whole chat here.
In short, you have a lot of problems there.
Are you still basing your code on the code from post #22?
If that is the case; than read this:

PWM & I2S Conflicts
Problem: The PWM (LEDC) and I2S DAC both use the internal DAC (GPIO 25 & 26).
Fix: If using I2S DAC, avoid PWM on DAC pins (25, 26). Use external PWM drivers if needed.

Sample Rate Mismatch
Problem: The I2S sample rate (400 kHz) is much higher than the PWM frequency (16 kHz).
Fix: Align the I2S rate with the PWM frequency to avoid aliasing.

Waveform Efficiency
Problem: The linear ramp (wave_data1) may not be optimal for metal detection.
Fix: Use only sine waves (wave_data2) for better sensitivity.

Floating Variables
Problem: i is declared globally but unused.
Fix: Remove unused variables to save memory.

The issue you're facing is that changing the amplitude in software doesn't affect the actual output voltage when
using the ESP32's built-in DAC.
This happens because the I2S DAC has a fixed output range (0–3.3V) and does not allow direct amplitude modulation
in the same way a PWM or external DAC would.

Why Amplitude Doesn’t Change
ESP32’s DAC is 8-bit (0–255) → Fixed 0–3.3V range.
Even if you reduce values in software (e.g., amp = 60), the DAC still outputs 0–3.3V, just with fewer steps.
The perceived amplitude (peak-to-peak voltage) remains the same.
I2S DAC Mode Limitations
The built-in DAC does not support variable reference voltage (unlike external DACs).

Solutions to Control Amplitude
1. Use PWM + Filtering (Best for Adjustable Amplitude)
If you need true amplitude control, use PWM + an RC low-pass filter instead of the I2S DAC.

[pito]

Manually I can change amplitude

int amp = 128;// 10 to 128 = 1/2 of 256 ,20 =0.52 Vpp, 40 = 1Vpp,128 = 3.28Vpp

but using the buttons I have a problem, even serial monitor is blank, no reaction on button pressing.

void ampchanges ()
{
  int amp;
  if (digitalRead(32) == LOW)
  {
    amp++;
  }
  if (digitalRead(33) == LOW)
  {
    amp--;
  }
  Serial.print("amp  = ");
  Serial.println(amp);
}​

[pito]

//https://esp32.com/viewtopic.php?p=144590&hilit=sin#p144590
#include "driver/i2s.h"
////////////////////////
#include <driver/ledc.h>
////////////////////////
#define SAMPLE_RATE 4000000
//#define WAVEFORM_SAMPLES 256            //3kHz
//#define WAVEFORM_SAMPLES 100            // 8kHz
//#define WAVEFORM_SAMPLES 50               //16 kHz
///////////////////////////
#define WAVEFORM_SAMPLES 400           // 500 = 16kHz, 400 = 20kHz
//#define SAMPLES 130
int amp = 128;// 10 to 128 = 1/2 of 256 ,20 =0.52 Vpp, 40 = 1Vpp,128 = 3.28Vpp
int cnt = 0;
int time_track = 0;
float stp = 6.2831 / WAVEFORM_SAMPLES;

uint8_t stereo_buffer[WAVEFORM_SAMPLES * 2];
uint8_t wave_data1[WAVEFORM_SAMPLES];
uint8_t wave_data2[WAVEFORM_SAMPLES];

void generateWaveforms() {
  //for (int i = 0; i < WAVEFORM_SAMPLES; i++)
  for (int i = 0; i < WAVEFORM_SAMPLES; i++)
  {
    wave_data1[i] = (uint8_t)(amp * (1 + sin(stp * i)));  //127.5; // Half of the max value (255/2)
    wave_data2[i] = (uint8_t)(amp * (1 + sin(stp * i)));
     // wave_data2[i] = (uint8_t)(100 * (1 + cos(stp * i)));
    // int dutyCycle = (int)(amp + amp * sin(stp * i)); //
  }

  for (int i = 0; i < WAVEFORM_SAMPLES; i++) {
    stereo_buffer[i * 2] = wave_data1[i];      // DAC1
    stereo_buffer[i * 2 + 1] = wave_data2[i];  // DAC2
  }
}

void setup() {
  Serial.begin(115200);
  //////////////////////
  ledc_timer_config_t timerConfig = {
    .speed_mode = LEDC_LOW_SPEED_MODE,
    .duty_resolution = LEDC_TIMER_10_BIT,
    .timer_num = LEDC_TIMER_0,
    .freq_hz = 8000,
    .clk_cfg = LEDC_AUTO_CLK
  };
  ledc_timer_config(&timerConfig);


  ledc_channel_config_t channelConfig1 = {
    .gpio_num = 12,
    .speed_mode = LEDC_LOW_SPEED_MODE,
    .channel = LEDC_CHANNEL_0,
    .timer_sel = LEDC_TIMER_0,
    .duty = 512,
    .hpoint = 0
  };
  ledc_channel_config(&channelConfig1);


  ledc_channel_config_t channelConfig2 = {
    .gpio_num = 14,
    .speed_mode = LEDC_LOW_SPEED_MODE,
    .channel = LEDC_CHANNEL_1,
    .timer_sel = LEDC_TIMER_0,
    .duty = 512,
    .hpoint = 256 // 90 deg
  };
  ledc_channel_config(&channelConfig2);
  /////////////////////////
  generateWaveforms();

  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_8BIT,
    .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
    .communication_format = I2S_COMM_FORMAT_I2S_MSB,
    .intr_alloc_flags = 0,
    .dma_buf_count = 8,
    .dma_buf_len = WAVEFORM_SAMPLES * 2,
    .use_apll = false,
  };

  i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
  i2s_set_pin(I2S_NUM_0, NULL);
  i2s_set_dac_mode(I2S_DAC_CHANNEL_BOTH_EN);
  i2s_set_sample_rates(I2S_NUM_0, i2s_config.sample_rate);
}

void loop() {
  size_t bytes_written;
  i2s_write(I2S_NUM_0, stereo_buffer, sizeof(stereo_buffer), &bytes_written, portMAX_DELAY);
}
//+++++++++++++++++++++++++++++++++++++++++++++++
void ampchanges ()
{
  int amp;
  if (digitalRead(32) == LOW)
  {
    amp++;
  }
  if (digitalRead(33) == LOW)
  {
    amp--;
  }
  Serial.print("amp  = ");
  Serial.println(amp);
}
​