Arduino Nano 33 BLE reading data from an electret microphone during a timer interrupt using the TimerInterrupt_Generic.h library

Hardware Nano Family Nano 33 BLE
1

Hello everyone, please tell me, I'm new to Arduino, I need to read data from an electret microphone during a timer interrupt, I found the TimerInterrupt_Generic.h library, tried to implement it with it, but nothing works, I understand the program just hangs. Here is a piece of my code:

NRF52_MBED_Timer ITimer0(NRF_TIMER_3);

void startRecording() {
  recording = true;
  startTime = millis();
  String newFileName = generateFileName(); 
  Serial.println(newFileName);
  myFile = SD.open("/samples/" + path + newFileName + ".wav", FILE_WRITE);  
  path = "";
  writeWavHeader();

  ITimer0.attachInterruptInterval(1000000 / 16000, timerISR);
}

void timerISR() {
  int micValue = analogRead(MIC_PIN);                          
  int16_t audioSample = map(micValue, 0, 1023, -32768, 32767);  

  if (useSampleBuffer1) {                           
    sampleBuffer1[sampleBufferIndex] = audioSample; 
    if (++sampleBufferIndex >= BUFFER_SIZE) {        
      sampleBuffer1Full = true;                      
      sampleBufferIndex = 0;                         
      useSampleBuffer1 = false;                 
    }
  } else {
    sampleBuffer2[sampleBufferIndex] = audioSample;
    if (++sampleBufferIndex >= BUFFER_SIZE) {
      sampleBuffer2Full = true;
      sampleBufferIndex = 0;
      useSampleBuffer1 = true;
    }
  }
}

I checked and the hang is already happening on this line:

 int micValue = analogRead(MIC_PIN);

I understand that interrupts are designed for short operations, but it is during the interruption that I need to read the value from the microphone and fill one of the two buffers, because I need to record data at a certain time interval, otherwise my data from the microphone will be recorded more often than necessary and as a result, the recording turns out to be incorrect if someone- anyone knows how to do this, please tell me, because I can't find anything about it. I saw a similar question on the forum and they wrote about low-level code, but I didn't understand how to do it anyway, thanks in advance, kind people

2

A basic rule of using interrupts is do not perform I/O inside one. I/O usually requires interrupts, which are turned off in the ISR.

I don't know if that is the case for analogRead on the Nano BLE 33, but the usual approach will still work: set a global flag variable, declared volatile, in the ISR. In the main program, check that flag and do the I/O when it is set.

There is very likely a way to connect the ADC and a timer directly, as timed analog reads are a very common task. The processor data sheet will have that info.