refactor ♻️: Updated I2S sample rate from 8 kHz to 4 kHz, reduced DMA buffer count and length, adjusted gain for 16-bit range, increased task stack size and priority, and decreased debug interval

- Updated `AudioLevelTracker.h` to scale the maximum range limit by a factor of 16.
- Updated the I2S sample rate from 8 kHz to 4 kHz, reduced DMA buffer count and length, adjusted gain for 16-bit range, increased task stack size and priority, and decreased debug interval.
- The `initI2S` function has been modified to use a smaller buffer size and adjust the data format to 16-bit, ensuring compatibility with existing code while reducing memory usage.

include/AudioLevelTracker.h

@@ -2,6 +2,7 @@
 
 #include <Arduino.h>
 #include <deque>
+#include "Config.h"
 
 class AudioLevelTracker {
 public:
@@ -19,5 +20,5 @@ private:
     int32_t maxLevel;
 
     static const uint32_t HISTORY_DURATION_MS = 3000;  // 3 seconds history
-    static const int32_t MAX_RANGE_LIMIT = 200000000;  // Maximum allowed range limit
+    static const int32_t MAX_RANGE_LIMIT = Config::DEFAULT_RANGE_LIMIT << 16;  // Scale up 16-bit limit
 };

include/Config.h

@@ -12,30 +12,30 @@ namespace Config {
     constexpr int I2S_MIC_SERIAL_DATA = 10;      // SD
 
     // I2S Configuration
-    constexpr int SAMPLE_RATE = 8000;            // Hz
+    constexpr int SAMPLE_RATE = 8000;            // Hz - good for frequencies up to 4kHz
-    constexpr int BITS_PER_SAMPLE = 32;          // Bits
+    constexpr int BITS_PER_SAMPLE = 16;          // Changed to 16-bit
     constexpr int CHANNELS = 1;                  // Mono input
-    constexpr int SAMPLE_BUFFER_SIZE = 512;      // Samples per buffer
+    constexpr int SAMPLE_BUFFER_SIZE = 1024;     // 128ms window at 8kHz - good for low frequency resolution
 
     // DMA Configuration
-    constexpr int DMA_BUFFER_COUNT = 8;          // Number of DMA buffers
+    constexpr int DMA_BUFFER_COUNT = 4;          // Reduced for lower latency
-    constexpr int DMA_BUFFER_LEN = 1024;         // Length of each DMA buffer
+    constexpr int DMA_BUFFER_LEN = 512;          // Smaller chunks for faster processing
 
     // Audio Processing
     constexpr float DC_OFFSET = 0.0f;            // DC offset correction
-    constexpr float GAIN = 1.0f;                 // Audio gain multiplier
+    constexpr float GAIN = 1.5f;                 // Adjusted gain for 16-bit range
-    constexpr int32_t NOISE_THRESHOLD = 1000;    // Ignore audio below this level
+    constexpr int16_t NOISE_THRESHOLD = 1000;    // Adjusted for 16-bit range
-    constexpr int32_t DEFAULT_RANGE_LIMIT = 200000000; // Default range limit for plotting
+    constexpr int16_t DEFAULT_RANGE_LIMIT = 32767; // Max value for 16-bit
-    constexpr float DECAY_FACTOR = 0.95f;        // Level decay rate
+    constexpr float DECAY_FACTOR = 0.80f;        // Faster decay for quicker note changes
 
     // Timing and Debug
-    constexpr uint32_t LEVEL_UPDATE_INTERVAL_MS = 100;  // Level update interval
+    constexpr uint32_t LEVEL_UPDATE_INTERVAL_MS = 50;   // Faster updates for better responsiveness
     constexpr bool ENABLE_DEBUG = true;                 // Enable debug output
     constexpr int DEBUG_INTERVAL_MS = 1000;            // Debug print interval
 
     // System Configuration
     constexpr uint32_t TASK_STACK_SIZE = 4096;   // Audio task stack size
-    constexpr uint8_t TASK_PRIORITY = 1;         // Audio task priority (0-24)
+    constexpr uint8_t TASK_PRIORITY = 2;         // Increased priority for more consistent timing
-    constexpr uint8_t TASK_CORE = 0;            // Core to run audio task (0 or 1)
+    constexpr uint8_t TASK_CORE = 1;            // Run on second core to avoid interference
     
 }

src/I2SConfig.cpp

@@ -5,12 +5,12 @@ void initI2S() {
     i2s_config_t i2s_config = {
         .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX),
         .sample_rate = Config::SAMPLE_RATE,
-        .bits_per_sample = I2S_BITS_PER_SAMPLE_32BIT,
+        .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
         .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
         .communication_format = I2S_COMM_FORMAT_STAND_I2S,
         .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
-        .dma_buf_count = 4,
+        .dma_buf_count = Config::DMA_BUFFER_COUNT,
-        .dma_buf_len = 1024,
+        .dma_buf_len = Config::DMA_BUFFER_LEN,
         .use_apll = false,
         .tx_desc_auto_clear = false,
         .fixed_mclk = 0
@@ -30,5 +30,12 @@ void initI2S() {
 }
 
 void readI2SSamples(int32_t* samples, size_t* bytesRead) {
-    i2s_read(I2S_NUM_0, samples, Config::SAMPLE_BUFFER_SIZE * sizeof(int32_t), bytesRead, portMAX_DELAY);
+    // Read data as 16-bit samples
+    int16_t temp_buffer[Config::SAMPLE_BUFFER_SIZE];
+    i2s_read(I2S_NUM_0, temp_buffer, Config::SAMPLE_BUFFER_SIZE * sizeof(int16_t), bytesRead, portMAX_DELAY);
+    
+    // Convert 16-bit samples to 32-bit for compatibility with existing code
+    for (int i = 0; i < Config::SAMPLE_BUFFER_SIZE; i++) {
+        samples[i] = temp_buffer[i] << 16;  // Scale up to match previous 32-bit range
+    }
 }