How do I print microphone input to the serial port of arduino nano 33 ble sense?

Good day,

I have an arduino nano 33 ble sense with a microphone on it. Using the PDM.h library I extract the audio into a sample buffer 512 bytes at a time. I use a type of ping pong buffer to save data while I print to the serial port but it keeps crashing, what did I do wrong?

#include <PDM.h>
#include <stdlib.h>

// buffer to read samples into, each sample is 16-bits
char sampleBuffer[512];

//ping pong buffer
//total bytes is how many bytes the microphone recorded
//write offset switches between first or second half of the ping pong buffer
//read offset switches between first or second half of the ping pong buffer
//ready to print indicates that the data is ready to print
char audio[66000];
long int totalBytes = 0;
int writeOffset = 0;
int readOffset = 0;
int half = 32768;
bool readyToPrint = false;


void setup() {

  //the sample rate is 16Khz with a 16-bit depth that means 32KBytes/s are needed to fully transfer this signal
  //the baud rate represents the bit rate of the signal, 32*8 is 256Kbits/s, closest compatible baud rate of the nano is 500kbaud
  Serial.begin(500000);
  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, 16000)) {
    Serial.println("Failed to start PDM!");
    while (1);
  }
}

void loop() {
}

void printToSerial(){
  Serial.write(audio + readOffset, half);
  readOffset = readOffset ^ half;
}

void onPDMdata() {
  // query the number of bytes available
  int bytesAvailable = PDM.available();

  // read into the sample buffer
  PDM.read(sampleBuffer, bytesAvailable);
  

  if(totalBytes < half){
    memcpy(audio + writeOffset + totalBytes, sampleBuffer, bytesAvailable);
    totalBytes += bytesAvailable;
  }
  else{
    totalBytes = 0;
    writeOffset = writeOffset ^ half;
    printToSerial();
  }

}