ML Arduino for sound classification

[gulli_andrea]

I want to upload a pre-trained model for audio classification on an Arduino Nano 33 BLE.
I want to receive audio from its built-in microphone, put it in a tensor, let the model process it and have the output of its inference.
I am beginning to work on it based on this two codes: https://docs.arduino.cc/tutorials/nano-33-ble-sense/microphone-sensor and https://docs.arduino.cc/tutorials/nano-33-ble-sense/get-started-with-machine-learning. I have the model saved in model.h format.

When I run the following code, that does nothing but it is just the first step for have the communication with the microphone set and the ML variables defined, if #include <model.h> is uncommented, it returns me the following error, otherwise not. Why!?

#include <PDM.h>
#include <TensorFlowLite.h>
#include <tensorflow/lite/micro/all_ops_resolver.h>
#include <tensorflow/lite/micro/micro_error_reporter.h>
#include <tensorflow/lite/micro/micro_interpreter.h>
#include <tensorflow/lite/schema/schema_generated.h>
#include <tensorflow/lite/version.h>

#include <model.h>


// buffer to read samples into, each sample is 16-bits
short sampleBuffer[256];

// number of samples read
volatile int samplesRead;

// global variables used for TensorFlow Lite (Micro)
tflite::MicroErrorReporter tflErrorReporter;

// pull in all the TFLM ops, you can remove this line and
// only pull in the TFLM ops you need, if would like to reduce
// the compiled size of the sketch.
tflite::AllOpsResolver tflOpsResolver;
	
const tflite::Model* tflModel = nullptr;
tflite::MicroInterpreter* tflInterpreter = nullptr;
TfLiteTensor* tflInputTensor = nullptr;
TfLiteTensor* tflOutputTensor = nullptr;

// Create a static memory buffer for TFLM, the size may need to
// be adjusted based on the model you are using
constexpr int tensorArenaSize = 8 * 1024;
byte tensorArena[tensorArenaSize] __attribute__((aligned(16)));

// array to map gesture index to a name
const char* GESTURES[] = {
  "punch",
  "flex"
};

void setup() {
  Serial.begin(9600);
  while (!Serial);

  // configure the data receive callback
  PDM.onReceive(onPDMdata);

  // optionally set the gain, defaults to 20
  // PDM.setGain(30);

  // initialize PDM with:
  // - one channel (mono mode)
  // - a 16 kHz sample rate
  if (!PDM.begin(1, 8000)) {
    Serial.println("Failed to start PDM!");
    while (1);
  }
  // get the TFL representation of the model byte array
  //tflModel = tflite::GetModel(bees_model);
  //if (tflModel->version() != TFLITE_SCHEMA_VERSION) {
  //  Serial.println("Model schema mismatch!");
  //  while (1);
  //}
  // Create an interpreter to run the model
  //tflInterpreter = new tflite::MicroInterpreter(tflModel, tflOpsResolver, tensorArena, tensorArenaSize, &tflErrorReporter);
  // Allocate memory for the model's input and output tensors
  //tflInterpreter->AllocateTensors();
  // Get pointers for the model's input and output tensors
  //tflInputTensor = tflInterpreter->input(0);
  //tflOutputTensor = tflInterpreter->output(0);
}

void loop() {
  // wait for samples to be read
  if (samplesRead) {
    // print samples to the serial monitor or plotter
    for (int i = 0; i < samplesRead; i++) {
      Serial.println(sampleBuffer[i]);
      // check if the sound value is higher than 500
      if (sampleBuffer[i]>=500){
        digitalWrite(LEDR,LOW);
        digitalWrite(LEDG,HIGH);
        digitalWrite(LEDB,HIGH);
      }
      // check if the sound value is higher than 250 and lower than 500
      if (sampleBuffer[i]>=250 && sampleBuffer[i] < 500){
        digitalWrite(LEDB,LOW);
        digitalWrite(LEDR,HIGH);
        digitalWrite(LEDG,HIGH);
      }
      //check if the sound value is higher than 0 and lower than 250
      if (sampleBuffer[i]>=0 && sampleBuffer[i] < 250){
        digitalWrite(LEDG,LOW);
        digitalWrite(LEDR,HIGH);
        digitalWrite(LEDB,HIGH);
      }
    }
    // clear the read count
    samplesRead = 0;
  }
}

void onPDMdata(void) {
  // query the number of bytes available
  int bytesAvailable = PDM.available();
  // read into the sample buffer
  PDM.read(sampleBuffer, bytesAvailable);
  // 16-bit, 2 bytes per sample
  samplesRead = bytesAvailable / 2;
}

The error is:

ML_arduino_bees.ino: In function 'void setup()':
ML_arduino_bees.ino:52:17: error: 'onPDMdata' was not declared in this scope
   PDM.onReceive(onPDMdata);
                 ^~~~~~~~~
ML_arduino_bees.ino:52:17: note: suggested alternative: 'model_data'
   PDM.onReceive(onPDMdata);
                 ^~~~~~~~~
                 model_data

exit status 1

Compilation error: 'onPDMdata' was not declared in this scope