ESP32 NeoPixel Music Visualizer (Amplitude-Reactive)

// ESP32 amplitude-reactive NeoPixel visualizer with INMP441 I2S microphone
// This is volume/RMS reactive, not FFT or spectrum analysis.
#include <Adafruit_NeoPixel.h>
#include "driver/i2s.h"

const int I2S_BCLK = 14;
const int I2S_LRCLK = 15;
const int I2S_DATA = 32;
const int LED_PIN = 5;
const int LED_COUNT = 30;
const int BRIGHTNESS_CAP = 80;

Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);
int32_t samples[256];

void setupI2S() {
  i2s_config_t config = {};
  config.mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX);
  config.sample_rate = 16000;
  config.bits_per_sample = I2S_BITS_PER_SAMPLE_32BIT;
  config.channel_format = I2S_CHANNEL_FMT_ONLY_LEFT;
  config.communication_format = I2S_COMM_FORMAT_STAND_I2S;
  config.intr_alloc_flags = ESP_INTR_FLAG_LEVEL1;
  config.dma_buf_count = 4;
  config.dma_buf_len = 256;
  i2s_pin_config_t pins = {I2S_BCLK, I2S_LRCLK, I2S_DATA, I2S_PIN_NO_CHANGE};
  i2s_driver_install(I2S_NUM_0, &config, 0, nullptr);
  i2s_set_pin(I2S_NUM_0, &pins);
}

uint32_t wheel(byte pos) {
  pos = 255 - pos;
  if (pos < 85) return strip.Color(255 - pos * 3, 0, pos * 3);
  if (pos < 170) {
    pos -= 85;
    return strip.Color(0, pos * 3, 255 - pos * 3);
  }
  pos -= 170;
  return strip.Color(pos * 3, 255 - pos * 3, 0);
}

void setup() {
  Serial.begin(115200);
  setupI2S();
  strip.begin();
  strip.setBrightness(BRIGHTNESS_CAP);
  strip.clear();
  strip.show();
  Serial.println("Amplitude visualizer ready. External 5 V LED power required.");
}

void loop() {
  size_t bytesRead = 0;
  i2s_read(I2S_NUM_0, samples, sizeof(samples), &bytesRead, portMAX_DELAY);
  int count = bytesRead / sizeof(samples[0]);
  if (count <= 0) return;

  double sumSquares = 0;
  for (int i = 0; i < count; i++) {
    int32_t s = samples[i] >> 14;
    sumSquares += (double)s * (double)s;
  }
  float rms = sqrt(sumSquares / count);
  int lit = constrain(map((int)rms, 100, 6000, 0, LED_COUNT), 0, LED_COUNT);

  strip.clear();
  for (int i = 0; i < lit; i++) {
    strip.setPixelColor(i, wheel(map(i, 0, LED_COUNT - 1, 100, 0)));
  }
  strip.show();
  Serial.println(rms);
}