Which one is the working Due version?

Hardware Arduino Due
33

I tried this but unfortunately it looks like the internal RC oscillator isn't nearly accurate enough. Mine is about 10% slow :frowning:

void setup()
{
  Serial.begin(9600);
}

union urtc { 
  struct {
    byte secs,mins,hrs,pad;
  } time;
  long dat;
} rtc;

byte BCD2bin(byte b){return (b&15)+((b>>4)*10);}

void loop()
{
  rtc.dat=RTC->RTC_TIMR;
  
  Serial.print("At the third stroke, it will be ");
  Serial.print(BCD2bin(rtc.time.hrs));
  Serial.print(":");
  Serial.print(BCD2bin(rtc.time.mins));
  Serial.print(":");
  Serial.print(BCD2bin(rtc.time.secs));
  Serial.println(" imprecisely.");
}