MKRZERO RTC blocking I2S AudioOutI2S.play(waveFile)

Using Arduino Audio
1

Hello,

I have an odd issue with a MKRZERO. When I try to play an audio file after the internal RTC has been initialised, the WAV files won't play. See the rtc.begin() function call in the code below.
Configuration: MKRZERO and Adafruit MAX98357A I2S audio board.

#include <SD.h>               // SD card access library
#include <ArduinoSound.h>     // I2S sound interface library 
#include <RTCZero.h>          // Real Time Clock library


// SETUP Audio playback 
// filename of wave file to play
const char filename[] = "MUSIC.WAV";
// variable representing the Wave File
SDWaveFile waveFile;

// SETUP Real Time Clock
/* Create a RTC object */
RTCZero rtc;

/* Change these values to set the current initial time */
const byte seconds = 0;
const byte minutes = 0;
const byte hours = 16;

/* Change these values to set the current initial date */
const byte day = 15;
const byte month = 6;
const byte year = 15;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);     // Start Arduino serial port at 9,600 baud
//  SD.begin();             // Open the SD card
delay(500);

  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  // setup the SD card, depending on your shield of breakout board
  // you may need to pass a pin number in begin for SS
  Serial.print("Initializing SD card..z.");
  
  if (!SD.begin()) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");

 // create a SDWaveFile
  waveFile = SDWaveFile(filename);

  // check if the WaveFile is valid
  if (!waveFile) {
    Serial.println("wave file is invalid!");
    while (1); // do nothing
  }

  // print out some info. about the wave file
  Serial.print("Bits per sample = ");
  Serial.println(waveFile.bitsPerSample());

  long channels = waveFile.channels();
  Serial.print("Channels = ");
  Serial.println(channels);

  long sampleRate = waveFile.sampleRate();
  Serial.print("Sample rate = ");
  Serial.print(sampleRate);
  Serial.println(" Hz");

  long duration = waveFile.duration();
  Serial.print("Duration = ");
  Serial.print(duration);
  Serial.println(" seconds");

  // adjust the playback volume
  AudioOutI2S.volume(100);

  // check if the I2S output can play the wave file
  if (!AudioOutI2S.canPlay(waveFile)) {
    Serial.println("unable to play wave file using I2S!");
    while (1); // do nothing
  }

  // IF START PLAYBACK LOCATED HERE IT WORKS
  // start playback
  Serial.println("starting playback");
  AudioOutI2S.play(waveFile); 


  
  // Start the RTC
  rtc.begin(); // Initialize RTC

  // IF START PLAYBACK LOCATED HERE, after rtc.begin();, IT DOESN'T
  // start playback
//  Serial.println("starting playback");
//  AudioOutI2S.play(waveFile); 


  // Set the time
  rtc.setHours(hours);
  rtc.setMinutes(minutes);
  rtc.setSeconds(seconds);

  // Set the date
  rtc.setDay(day);
  rtc.setMonth(month);
  rtc.setYear(year);
   
  rtc.setAlarmTime(16, 0, 20);
  rtc.enableAlarm(rtc.MATCH_HHMMSS);
  rtc.attachInterrupt(alarmMatch);
}


void loop() {
  // put your main code here, to run repeatedly:

}


void alarmMatch()
{
  Serial.println("Alarm Match!");
}

Many thanks for any thoughts / assistance.