The AudioKit and some ESP32 Processors have 4MB of SPI RAM that we can use e.g. to store recorded audio. I was playing with the idea to build some looping logic. Therefore I have added an additional DynamicMemoryStream class that can stores the audio data on the heap. With the help of the memory manager we can indicate that data chunks that are above a specified limit are stored in SPI RAM!

Arduino Sketch

To get started here I have a simple test sketch that starts to record audio from the microphone when a button is pressed and stops the recording when the button is released. After that it plays the recorded sound in a loop:

#include "AudioTools.h"
#include "AudioLibs/AudioKit.h"
#include "AudioLibs/MemoryManager.h"

uint16_t sample_rate = 16000;
uint8_t channels = 1;  // The stream will have 1 channel
AudioKitStream kit;
MemoryManager memory(500); // Activate SPI RAM for objects > 500 bytes
DynamicMemoryStream recording(true); // Audio stored on heap looping endlessly 
StreamCopy copier; // copies data


void record_start(bool pinStatus, int pin, void* ref){
  Serial.println("Recording...");
  recording.begin(); // clear data
  copier.begin(recording, kit); // from mic to memory 
}

void record_end(bool pinStatus, int pin, void* ref){
  Serial.println("Playing...");
  copier.begin(kit, recording);  // from memory to kit
}

void setup(){
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Info);  

  // setup input and output
  auto cfg = kit.defaultConfig(RXTX_MODE);
  cfg.sd_active = false; // we don't need the SD card
  cfg.sample_rate = sample_rate; 
  cfg.channels = channels;
  cfg.input_device = AUDIO_HAL_ADC_INPUT_LINE2;
  kit.begin(cfg);
  kit.setVolume(1.0);

  // record when key 1 is pressed
  kit.audioActions().add(PIN_KEY1, record_start, record_end);
  Serial.println("Press Key 1 to record");

}

void loop(){
  // record or play recording
  copier.copy();  

  // Process keys
  kit.processActions();
}

The complete potentially updated example can be found on Github


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