StickC-Plus SE Microphone

#include <M5Unified.h>

static constexpr const size_t record_number = 200;   // more may fail on ESP32-PICO-D4
static constexpr const size_t record_length = 240;
static constexpr const size_t record_size = record_number * record_length;
static constexpr const size_t record_samplerate = 17000;

static int16_t prev_y[record_length];
static int16_t prev_h[record_length];

static size_t rec_record_idx = 2;
static size_t draw_record_idx = 0;
// Allocate the audio buffer dynamically to avoid reserving a large static RAM block.
static int16_t *rec_data = nullptr;

void showError(const char *msg) {
  // Show the error on the display and stop here so the board does not keep rebooting.
  M5.Display.clear();
  M5.Display.setTextDatum(middle_center);
  M5.Display.setTextColor(RED);
  M5.Display.drawString(msg, M5.Display.width() / 2, M5.Display.height() / 2);

  while (true) {
    delay(1000);
  }
}

void setup(void) {
  auto cfg = M5.config();
  M5.begin(cfg);

  M5.Display.startWrite();
  M5.Display.setRotation(1);
  M5.Display.setTextDatum(top_center);
  M5.Display.setTextColor(WHITE);
  M5.Display.setFont(&fonts::FreeSansBoldOblique12pt7b);

  // Allocate the recording ring buffer in internal 8-bit-capable RAM.
  rec_data = (int16_t *)heap_caps_malloc(record_size * sizeof(int16_t), MALLOC_CAP_8BIT);

  if (rec_data == nullptr) {
    showError("malloc failed");
  }

  memset(rec_data, 0, record_size * sizeof(int16_t));

  M5.Speaker.setVolume(255);

  // Disable the speaker because the microphone and speaker cannot be used at the same time.
  M5.Speaker.end();

  if (!M5.Mic.begin()) {
    showError("Mic begin failed");
  }

  M5.Display.clear();
  M5.Display.fillCircle(70, 15, 8, RED);
  M5.Display.drawString("REC", 120, 3);
}

void loop(void) {
  M5.update();

  if (M5.Mic.isEnabled() && rec_data != nullptr) {
    // Record one block, then draw the previous block to keep recording and display updates smooth.
    static constexpr int shift = 6;

    auto data = &rec_data[rec_record_idx * record_length];

    if (M5.Mic.record(data, record_length, record_samplerate)) {
      data = &rec_data[draw_record_idx * record_length];

      int32_t w = M5.Display.width();
      if (w > record_length - 1) {
        w = record_length - 1;
      }

      for (int32_t x = 0; x < w; ++x) {
        M5.Display.writeFastVLine(x, prev_y[x], prev_h[x], TFT_BLACK);

        int32_t y1 = data[x] >> shift;
        int32_t y2 = data[x + 1] >> shift;

        if (y1 > y2) {
          int32_t tmp = y1;
          y1 = y2;
          y2 = tmp;
        }

        int32_t y = (M5.Display.height() >> 1) + y1;
        int32_t h = (M5.Display.height() >> 1) + y2 + 1 - y;

        prev_y[x] = y;
        prev_h[x] = h;

        M5.Display.writeFastVLine(x, prev_y[x], prev_h[x], WHITE);
      }

      M5.Display.display();
      M5.Display.fillCircle(70, 15, 8, RED);
      M5.Display.drawString("REC", 120, 3);

      // Advance the recording and drawing positions in the ring buffer.
      if (++draw_record_idx >= record_number) {
        draw_record_idx = 0;
      }

      if (++rec_record_idx >= record_number) {
        rec_record_idx = 0;
      }
    }
  }

  if (M5.BtnA.wasHold()) {
    auto cfg = M5.Mic.config();
    cfg.noise_filter_level = (cfg.noise_filter_level + 8) & 255;
    M5.Mic.config(cfg);

    M5.Display.clear();
    M5.Display.fillCircle(70, 15, 8, GREEN);
    M5.Display.drawString("NF:" + String(cfg.noise_filter_level), 120, 3);

  } else if (M5.BtnA.wasClicked()) {
    if (rec_data == nullptr) {
      return;
    }

    M5.Display.clear();

    while (M5.Mic.isRecording()) {
      delay(1);
    }

    // Disable the microphone before playback because the microphone and speaker cannot be used at the same time.
    M5.Mic.end();

    if (!M5.Speaker.begin()) {
      showError("Speaker begin failed");
    }

    M5.Display.fillTriangle(70 - 8, 15 - 8, 70 - 8, 15 + 8, 70 + 8, 15, 0x1c9f);
    M5.Display.drawString("PLAY", 120, 3);

    int start_pos = rec_record_idx * record_length;

    // Play the ring buffer from the oldest sample to the newest sample.
    if (start_pos < record_size) {
      M5.Speaker.playRaw(&rec_data[start_pos], record_size - start_pos, record_samplerate, false, 1, 0);
    }

    if (start_pos > 0) {
      M5.Speaker.playRaw(rec_data, start_pos, record_samplerate, false, 1, 0);
    }

    do {
      delay(1);
      M5.update();
    } while (M5.Speaker.isPlaying());

    // Disable the speaker before switching back to recording.
    M5.Speaker.end();

    if (!M5.Mic.begin()) {
      showError("Mic begin failed");
    }

    M5.Display.clear();
    M5.Display.fillCircle(70, 15, 8, RED);
    M5.Display.drawString("REC", 120, 3);
  }
}