Unit Mini PDM Arduino Tutorial

#include <M5Unified.h> #define PIN_CLK 33 #define PIN_DATA 32 // Audio recording configuration constants static constexpr const size_t record_number = 256; // Number of recording buffers static constexpr const size_t record_length = 320; // Samples per buffer (recommended to match LCD width) static constexpr const size_t record_size = record_number * record_length; // Total recording size static constexpr const size_t record_samplerate = 16000; // Recording sample rate in Hz // Variables for waveform drawing static int16_t prev_y[record_length]; // Previous Y positions for waveform clearing static int16_t prev_h[record_length]; // Previous heights for waveform clearing static size_t rec_record_idx = 2; // Current recording buffer index static size_t draw_record_idx = 0; // Current buffer index for drawing static int16_t *rec_data; // Pointer to recording data buffer static int32_t w; // Display width void setup(void) { // Initialize M5 device with default configuration auto cfg = M5.config(); M5.begin(cfg); // Configure display M5.Display.setRotation(1); // Set display rotation w = M5.Display.width(); // Get display width M5.Display.startWrite(); // Start display write transaction M5.Display.setTextDatum(top_center);// Set text alignment M5.Display.setTextColor(TFT_WHITE); // Set text color M5.Display.setFont(&fonts::FreeSansBoldOblique9pt7b); // Set display font // Configure microphone settings m5::mic_config_t mic_cfg = { .pin_data_in = PIN_DATA, // Microphone data input pin .pin_bck = I2S_PIN_NO_CHANGE, // No change for I2S bit clock .pin_mck = I2S_PIN_NO_CHANGE, // No change for I2S master clock .pin_ws = PIN_CLK, // Microphone word select (clock) pin .sample_rate = record_samplerate, // Microphone sample rate in Hz .dma_buf_len = 128, // DMA buffer length .dma_buf_count = 2, // Number of DMA buffers .i2s_port = i2s_port_t::I2S_NUM_0 // I2S port number }; // Apply microphone configuration M5.Mic.config(mic_cfg); // Allocate memory for recording buffer rec_data = (typeof(rec_data))heap_caps_malloc(record_size * sizeof(int16_t), MALLOC_CAP_8BIT); memset(rec_data, 0, record_size * sizeof(int16_t)); // Initialize buffer to zero // Start microphone M5.Mic.begin(); // Display recording status indicators M5.Display.fillCircle(200, 28, 8, RED); M5.Display.drawString("REC", w / 2, 18); } void loop(void) { // Update M5 device state M5.update(); // Check if microphone is enabled if (M5.Mic.isEnabled()) { static constexpr int shift = 6; // Shift value for amplitude scaling auto data = &rec_data[rec_record_idx * record_length]; // Get current recording buffer // Record audio data into buffer if (M5.Mic.record(data, record_length)) { data = &rec_data[draw_record_idx * record_length]; // Get buffer for drawing // Ensure display width doesn't exceed buffer size if (w > record_length - 1) { w = record_length - 1; } // Draw audio waveform for (int32_t x = 0; x < w; ++x) { // Clear previous waveform at this X position M5.Display.writeFastVLine(x, prev_y[x], prev_h[x], TFT_BLACK); // Calculate waveform points (scaled by shift) int32_t y1 = (data[x] >> shift); int32_t y2 = (data[x + 1] >> shift); // Ensure y1 is the lower value if (y1 > y2) { int32_t tmp = y1; y1 = y2; y2 = tmp; } // Calculate display coordinates int32_t y = ((M5.Display.height()) >> 1) + y1; // Base Y position int32_t h = ((M5.Display.height()) >> 1) + y2 + 1 - y; // Waveform height // Store current values for next frame's clearing prev_y[x] = y; prev_h[x] = h; // Draw current waveform segment M5.Display.writeFastVLine(x, prev_y[x], prev_h[x], WHITE); } // Update display and maintain recording indicators M5.Display.display(); M5.Display.fillCircle(200, 28, 8, RED); // Red circle for recording status M5.Display.drawString("REC", w / 2, 18); // "REC" text indicator // Update buffer indices (wrap around when reaching end) if (++draw_record_idx >= record_number) { draw_record_idx = 0; } if (++rec_record_idx >= record_number) { rec_record_idx = 0; } } } } 

#include "driver/i2s_pdm.h" #include <M5Unified.h> #include <M5GFX.h> // Define microphone pins #define PIN_CLK GPIO_NUM_33 #define PIN_DATA GPIO_NUM_32 // Audio buffer and recording settings static constexpr const size_t record_number = 2; // Total number of recording buffers static constexpr const size_t record_length = 320; // Samples per buffer (should match display width) static constexpr const size_t record_size = record_number * record_length; // Total number of samples static constexpr const size_t record_samplerate = 16000; // Sample rate in Hz // Arrays used for clearing previous waveform lines static int16_t prev_y[record_length]; // Y-coordinates of previous frame lines static int16_t prev_h[record_length]; // Heights of previous frame lines // Indices for recording/drawing buffers static size_t rec_record_idx = 2; // Index to current input buffer static size_t draw_record_idx = 0; // Index to current drawing buffer static int16_t *rec_data; // Pointer to audio buffer static int32_t w; // Display width // I2S hardware handle for ESP32 i2s_chan_handle_t rx_handle = nullptr; #define I2S_PORT I2S_NUM_0 void setup(void) { // Initialize M5 hardware (screen, etc.) auto cfg = M5.config(); M5.begin(cfg); // Initialize display parameters M5.Display.setRotation(1); w = M5.Display.width(); M5.Display.startWrite(); M5.Display.setTextDatum(top_center); M5.Display.setTextColor(TFT_WHITE); M5.Display.setFont(&fonts::FreeSansBoldOblique9pt7b); // Create I2S channel i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_PORT, I2S_ROLE_MASTER); ESP_ERROR_CHECK(i2s_new_channel(&chan_cfg, NULL, &rx_handle)); // Configure PDM microphone parameters (clock, slots, gpio) i2s_pdm_rx_config_t pdm_rx_cfg = { .clk_cfg = I2S_PDM_RX_CLK_DEFAULT_CONFIG(record_samplerate), .slot_cfg = I2S_PDM_RX_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO), .gpio_cfg = { .clk = PIN_CLK, .din = PIN_DATA, .invert_flags = {.clk_inv = false }, } }; ESP_ERROR_CHECK(i2s_channel_init_pdm_rx_mode(rx_handle, &pdm_rx_cfg)); ESP_ERROR_CHECK(i2s_channel_enable(rx_handle)); // Allocate memory for audio buffer and clear it rec_data = (typeof(rec_data))heap_caps_malloc(record_size * sizeof(int16_t), MALLOC_CAP_8BIT); memset(rec_data, 0, record_size * sizeof(int16_t)); // Draw recording status indicators M5.Display.fillCircle(200, 28, 8, RED); M5.Display.drawString("REC", w / 2, 18); } // Read one frame of audio from microphone bool mic_record(int16_t* buf, size_t samples) { size_t bytes_to_read = samples * sizeof(int16_t); size_t bytes_read = 0; esp_err_t ret = i2s_channel_read(rx_handle, (void*)buf, bytes_to_read, &bytes_read, 50 / portTICK_PERIOD_MS); return (ret == ESP_OK && bytes_read == bytes_to_read); } void loop(void) { M5.update(); // Update button/status of M5 static constexpr int shift = 6; // Used for amplitude scaling (bit shift) auto data = &rec_data[rec_record_idx * record_length]; // Pointer to current record buffer // Record new audio data into buffer if (mic_record(data, record_length)) { data = &rec_data[draw_record_idx * record_length]; // Set pointer to buffer for drawing if (w > record_length - 1) { w = record_length - 1; } // Draw waveform on display buffer for (int32_t x = 0; x < w; ++x) { // Erase previous waveform line at position x M5.Display.writeFastVLine(x, prev_y[x], prev_h[x], TFT_BLACK); // Get two consecutive samples, scale down via shift int32_t y1 = (data[x] >> shift); int32_t y2 = (data[x + 1] >> shift); // Ensure y1<=y2 for drawing from low to high if (y1 > y2) { int32_t tmp = y1; y1 = y2; y2 = tmp; } // Calculate line's start vertical position and height int32_t y = ((M5.Display.height()) >> 1) + y1; // Vertical origin is center int32_t h = ((M5.Display.height()) >> 1) + y2 + 1 - y; // Store for later clearing prev_y[x] = y; prev_h[x] = h; // Draw current waveform line in white M5.Display.writeFastVLine(x, prev_y[x], prev_h[x], TFT_WHITE); } // Commit display changes and redraw recording status M5.Display.display(); M5.Display.fillCircle(200, 28, 8, RED); M5.Display.drawString("REC", w / 2, 18); // Move indices to next buffer, wrap around if necessary if (++draw_record_idx >= record_number) { draw_record_idx = 0; } if (++rec_record_idx >= record_number) { rec_record_idx = 0; } } }

#include <SPI.h> #include <SD.h> #include <M5Unified.h> // Pin definitions for SD card SPI communication #define SD_SPI_CS_PIN 4  #define SD_SPI_SCK_PIN 18  #define SD_SPI_MISO_PIN 38  #define SD_SPI_MOSI_PIN 23  // Pin definitions for microphone I2S communication #define MIC_I2S_PIN_CLK 33  #define MIC_I2S_PIN_DATA 32  // Audio recording configuration parameters static constexpr size_t record_number = 16; // Number of recording buffers static constexpr size_t record_length = 512; // Sample length per recording static constexpr size_t record_samplerate = 16000; // Recording sample rate in Hz static constexpr uint8_t bitsPerSample = 16; // Bits per audio sample static constexpr uint8_t numChannels = 1; // Number of audio channels (1 = mono) // Global variables for recording static int16_t *rec_data; // Buffer to store recorded audio data static bool isRecording = false; // Flag indicating recording state static size_t totalSamples = 0; // Total number of recorded samples unsigned long record_start_ms = 0; // Timestamp when recording started static int32_t w; // Display width // Structure defining WAV file header format struct WavHeader { char riff[4]; // "RIFF" identifier uint32_t fileSize; // Total file size minus 8 char wave[4]; // "WAVE" identifier char fmt[4]; // "fmt " identifier uint32_t fmtSize; // Size of the format chunk uint16_t format; // Audio format (1 = PCM) uint16_t channels; // Number of audio channels uint32_t sampleRate; // Audio sample rate uint32_t byteRate; // Byte rate (sampleRate * channels * bitsPerSample/8) uint16_t blockAlign; // Block alignment (channels * bitsPerSample/8) uint16_t bitsPerSample;// Bits per sample char data[4]; // "data" identifier uint32_t dataSize; // Size of the audio data }; /** * Writes the WAV file header to the specified file * @param file File object to write header to * @param pcmBytes Total size of PCM audio data in bytes */ void writeWavHeader(File &file, uint32_t pcmBytes) { WavHeader header; memcpy(header.riff, "RIFF", 4); header.fileSize = 36 + pcmBytes; // Calculate total file size memcpy(header.wave, "WAVE", 4); memcpy(header.fmt, "fmt ", 4); header.fmtSize = 16; // PCM format chunk size header.format = 1; // PCM format header.channels = numChannels; header.sampleRate = record_samplerate; header.byteRate = record_samplerate * numChannels * (bitsPerSample / 8); header.blockAlign = numChannels * (bitsPerSample / 8); header.bitsPerSample = bitsPerSample; memcpy(header.data, "data", 4); header.dataSize = pcmBytes; file.seek(0); // Move to start of file file.write((const uint8_t*)&header, sizeof(WavHeader)); // Write header } File wavFile; // File object for WAV recording void setup(void) { auto cfg = M5.config(); // Get default M5 configuration M5.begin(cfg); // Initialize M5Stack device M5.Display.setRotation(1); // Set display rotation w = M5.Display.width(); // Get display width M5.Display.setTextDatum(top_center); // Set text alignment M5.Display.setTextColor(TFT_BLACK, TFT_WHITE); // Set text colors M5.Display.setFont(&fonts::FreeSansBoldOblique9pt7b); // Set font // Initialize SD card SPI.begin(SD_SPI_SCK_PIN, SD_SPI_MISO_PIN, SD_SPI_MOSI_PIN, SD_SPI_CS_PIN); M5.Display.drawCenterString("SD Initializing...", w/2, 0); if (!SD.begin(SD_SPI_CS_PIN, SPI, 25000000)) { // Attempt to initialize SD card M5.Display.drawCenterString("SD Init Error!", w/2, 50); while (1); // Halt if SD card initialization fails } else { M5.Display.drawCenterString("SD Ready", w/2, 30); } // Configure microphone m5::mic_config_t mic_cfg = { .pin_data_in = MIC_I2S_PIN_DATA, .pin_bck = I2S_PIN_NO_CHANGE, .pin_mck = I2S_PIN_NO_CHANGE, .pin_ws = MIC_I2S_PIN_CLK, .sample_rate = record_samplerate, .dma_buf_len = 128, .dma_buf_count = 8, .i2s_port = I2S_NUM_0 }; M5.Mic.config(mic_cfg); // Apply microphone configuration M5.Mic.begin(); // Initialize microphone if (M5.Mic.isEnabled()) { // Check if microphone initialized successfully M5.Display.drawCenterString("Mic Ready", w/2, 50); } M5.Mic.end(); // Temporary stop microphone delay(500); // Allocate memory for audio recording buffer rec_data = (int16_t*)heap_caps_malloc( record_length * sizeof(int16_t), MALLOC_CAP_8BIT | MALLOC_CAP_32BIT ); if (!rec_data) { // Check if memory allocation failed M5.Display.drawCenterString("Memory Alloc Error", w/2, 60); while (1); // Halt if memory allocation fails } memset(rec_data, 0, record_length * sizeof(int16_t)); // Initialize buffer to zero M5.Display.clear(TFT_WHITE); // Display usage instructions M5.Display.drawCenterString("Mic Recording Example", w/2, 10); M5.Display.drawCenterString("Start Stop", w/2, 210); } void loop(void) { M5.update(); // Update M5Stack device state (buttons, sensors, etc.) //----------------- Start recording when Button A is pressed ----------------- if (M5.BtnA.wasClicked() && !isRecording) { M5.Display.fillRect(0, 110, w, 100, TFT_WHITE); // Clear previous status isRecording = true; totalSamples = 0; // Remove existing file if it exists if (SD.exists("/recording.wav")) { SD.remove("/recording.wav"); M5.Display.drawCenterString("Old File Deleted", w/2, 80); } // Open new file for writing wavFile = SD.open("/recording.wav", FILE_WRITE); if (!wavFile) { // Check if file opened successfully M5.Display.drawCenterString("Create WAV File Error!", w/2, 100); isRecording = false; return; } // Write temporary header (will be updated at end of recording) writeWavHeader(wavFile, 0); // Start microphone and begin recording if (M5.Mic.begin()) { record_start_ms = millis(); M5.Display.drawCenterString("Recording...", w/2, 160); } else { M5.Display.drawCenterString("Mic Start Error!", w/2, 160); isRecording = false; wavFile.close(); } delay(15); } //----------------- Stop recording when Button C is pressed ----------------- if (M5.BtnC.wasClicked() && isRecording) { isRecording = false; } //----------------- Recording process (synchronous task) ----------------- if (isRecording && M5.Mic.isEnabled() && wavFile) { // Submit recording block task bool submitted = M5.Mic.record(rec_data, record_length); if (submitted) { // Wait for recording to complete while (M5.Mic.isRecording()) { vTaskDelay(2); // Short delay to reduce CPU usage } // Write recorded data to file size_t written = wavFile.write((const uint8_t*)rec_data, record_length * sizeof(int16_t)); totalSamples += record_length; // Display recording status: time and file size float sec = ((float)totalSamples) / record_samplerate; uint32_t pcmBytes = totalSamples * sizeof(int16_t); char info[64]; sprintf(info, "Time: %.2fs Size:%dKB", sec, pcmBytes/1024); M5.Display.drawCenterString(info, w/2, 110); } else { M5.Display.drawCenterString("Mic Record Fail!", w/2, 110); vTaskDelay(10); } // Short delay between recording blocks to reduce SD card stress vTaskDelay(5); } //------------------- Finalize recording and update file header ------------------ if (!isRecording && wavFile) { M5.Mic.end(); // Stop microphone // Calculate total audio data size and update WAV header uint32_t pcmBytes = totalSamples * sizeof(int16_t); writeWavHeader(wavFile, pcmBytes); wavFile.close(); wavFile = File(); // Clear file handle // Display recording summary float sec = ((float)totalSamples) / record_samplerate; char info[64]; sprintf(info, "New WAV Saved: %.2fs, %dKB", sec, pcmBytes/1024); M5.Display.drawCenterString(info, w/2, 160); delay(35); } }

#include <SPI.h> #include <SD.h> #include <driver/i2s_pdm.h> #include <M5Unified.h> // Pin definitions for SD card SPI communication #define SD_SPI_CS_PIN 4  #define SD_SPI_SCK_PIN 18  #define SD_SPI_MISO_PIN 38  #define SD_SPI_MOSI_PIN 23  // Pin definitions for microphone I2S communication #define MIC_I2S_PIN_CLK GPIO_NUM_33  #define MIC_I2S_PIN_DATA GPIO_NUM_32  // Audio recording configuration parameters static constexpr size_t record_number = 16; // Number of recording buffers static constexpr size_t record_length = 512; // Sample length per recording static constexpr size_t record_samplerate = 16000; // Recording sample rate in Hz static constexpr uint8_t bitsPerSample = 16; // Bits per audio sample static constexpr uint8_t numChannels = 1; // Number of audio channels (1 = mono) // Global variables for recording static int16_t *rec_data; // Buffer to store recorded audio data static bool isRecording = false; // Flag indicating recording state static size_t totalSamples = 0; // Total number of recorded samples unsigned long record_start_ms = 0; // Timestamp when recording started static int32_t w; // Display width // I2S hardware handle for ESP32 i2s_chan_handle_t rx_handle = nullptr; #define I2S_PORT I2S_NUM_0 // Structure defining WAV file header format struct WavHeader { char riff[4]; // "RIFF" identifier uint32_t fileSize; // Total file size minus 8 char wave[4]; // "WAVE" identifier char fmt[4]; // "fmt " identifier uint32_t fmtSize; // Size of the format chunk uint16_t format; // Audio format (1 = PCM) uint16_t channels; // Number of audio channels uint32_t sampleRate; // Audio sample rate uint32_t byteRate; // Byte rate (sampleRate * channels * bitsPerSample/8) uint16_t blockAlign; // Block alignment (channels * bitsPerSample/8) uint16_t bitsPerSample;// Bits per sample char data[4]; // "data" identifier uint32_t dataSize; // Size of the audio data }; /** * Writes the WAV file header to the specified file * @param file File object to write header to * @param pcmBytes Total size of PCM audio data in bytes */ void writeWavHeader(File &file, uint32_t pcmBytes) { WavHeader header; memcpy(header.riff, "RIFF", 4); header.fileSize = 36 + pcmBytes; // Calculate total file size memcpy(header.wave, "WAVE", 4); memcpy(header.fmt, "fmt ", 4); header.fmtSize = 16; // PCM format chunk size header.format = 1; // PCM format header.channels = numChannels; header.sampleRate = record_samplerate; header.byteRate = record_samplerate * numChannels * (bitsPerSample / 8); header.blockAlign = numChannels * (bitsPerSample / 8); header.bitsPerSample = bitsPerSample; memcpy(header.data, "data", 4); header.dataSize = pcmBytes; file.seek(0); // Move to start of file file.write((const uint8_t*)&header, sizeof(WavHeader)); // Write header } File wavFile; // File object for WAV recording void setup(void) { auto cfg = M5.config(); // Get default M5 configuration M5.begin(cfg); // Initialize M5Stack device M5.Display.setRotation(1); // Set display rotation w = M5.Display.width(); // Get display width M5.Display.setTextDatum(top_center); // Set text alignment M5.Display.setTextColor(TFT_BLACK, TFT_WHITE); // Set text colors M5.Display.setFont(&fonts::FreeSansBoldOblique9pt7b); // Set font // Initialize SD card SPI.begin(SD_SPI_SCK_PIN, SD_SPI_MISO_PIN, SD_SPI_MOSI_PIN, SD_SPI_CS_PIN); M5.Display.drawCenterString("SD Initializing...", w/2, 0); if (!SD.begin(SD_SPI_CS_PIN, SPI, 25000000)) { // Attempt to initialize SD card M5.Display.drawCenterString("SD Init Error!", w/2, 50); while (1); // Halt if SD card initialization fails } else { M5.Display.drawCenterString("SD Ready", w/2, 30); } // Create I2S channel i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_PORT, I2S_ROLE_MASTER); ESP_ERROR_CHECK(i2s_new_channel(&chan_cfg, NULL, &rx_handle)); // Configure PDM microphone parameters (clock, slots, gpio) i2s_pdm_rx_config_t pdm_rx_cfg = { .clk_cfg = I2S_PDM_RX_CLK_DEFAULT_CONFIG(record_samplerate), .slot_cfg = I2S_PDM_RX_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO), .gpio_cfg = { .clk = MIC_I2S_PIN_CLK, .din = MIC_I2S_PIN_DATA, .invert_flags = {.clk_inv = false }, } }; ESP_ERROR_CHECK(i2s_channel_init_pdm_rx_mode(rx_handle, &pdm_rx_cfg)); ESP_ERROR_CHECK(i2s_channel_enable(rx_handle)); // Allocate memory for audio recording buffer rec_data = (int16_t*)heap_caps_malloc( record_length * sizeof(int16_t), MALLOC_CAP_8BIT | MALLOC_CAP_32BIT ); if (!rec_data) { // Check if memory allocation failed M5.Display.drawCenterString("Memory Alloc Error", w/2, 60); while (1); // Halt if memory allocation fails } memset(rec_data, 0, record_length * sizeof(int16_t)); // Initialize buffer to zero M5.Display.clear(TFT_WHITE); // Display usage instructions M5.Display.drawCenterString("Mic Recording Example", w/2, 10); M5.Display.drawCenterString("Start Stop", w/2, 210); } // Read one frame of audio from microphone bool mic_record(int16_t* buf, size_t samples) { size_t bytes_to_read = samples * sizeof(int16_t); size_t bytes_read = 0; esp_err_t ret = i2s_channel_read(rx_handle, (void*)buf, bytes_to_read, &bytes_read, 50 / portTICK_PERIOD_MS); return (ret == ESP_OK && bytes_read == bytes_to_read); } void loop(void) { M5.update(); // Update M5Stack device state (buttons, sensors, etc.) //----------------- Start recording when Button A is pressed ----------------- if (M5.BtnA.wasClicked() && !isRecording) { M5.Display.fillRect(0, 110, w, 100, TFT_WHITE); // Clear previous status isRecording = true; totalSamples = 0; // Remove existing file if it exists if (SD.exists("/recording.wav")) { SD.remove("/recording.wav"); M5.Display.drawCenterString("Old File Deleted", w/2, 80); } // Open new file for writing wavFile = SD.open("/recording.wav", FILE_WRITE); if (!wavFile) { // Check if file opened successfully M5.Display.drawCenterString("Create WAV File Error!", w/2, 100); isRecording = false; return; } // Write temporary header (will be updated at end of recording) writeWavHeader(wavFile, 0); record_start_ms = millis(); M5.Display.drawCenterString("Recording...", w/2, 160); delay(15); } //----------------- Stop recording when Button C is pressed ----------------- if (M5.BtnC.wasClicked() && isRecording) { isRecording = false; } //----------------- Recording process (synchronous task) ----------------- if (isRecording && wavFile) { // Submit recording block task bool submitted = mic_record(rec_data, record_length); if (submitted) { // Write recorded data to file size_t written = wavFile.write((const uint8_t*)rec_data, record_length * sizeof(int16_t)); totalSamples += record_length; // Display recording status: time and file size float sec = ((float)totalSamples) / record_samplerate; uint32_t pcmBytes = totalSamples * sizeof(int16_t); char info[64]; sprintf(info, "Time: %.2fs Size:%dKB", sec, pcmBytes/1024); M5.Display.drawCenterString(info, w/2, 110); } else { M5.Display.drawCenterString("Mic Record Fail!", w/2, 110); vTaskDelay(10); } // Short delay between recording blocks to reduce SD card stress vTaskDelay(5); } //------------------- Finalize recording and update file header ------------------ if (!isRecording && wavFile) { M5.Mic.end(); // Stop microphone // Calculate total audio data size and update WAV header uint32_t pcmBytes = totalSamples * sizeof(int16_t); writeWavHeader(wavFile, pcmBytes); wavFile.close(); wavFile = File(); // Clear file handle // Display recording summary float sec = ((float)totalSamples) / record_samplerate; char info[64]; sprintf(info, "New WAV Saved: %.2fs, %dKB", sec, pcmBytes/1024); M5.Display.drawCenterString(info, w/2, 160); delay(35); } }