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){
  recording.begin(); // clear data
  copier.begin(recording, kit); // from mic to memory 

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

void setup(){
  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;

  // 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

  // Process keys

The complete potentially updated example can be found on Github


David · 11. October 2023 at 21:30

does the code can work with a esp32 only ? (no audio kit board)

    pschatzmann · 12. October 2023 at 3:01

    it will work with any ESP32 board that has PSRAM. This includes the AudioKit board.

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