ArduinoDue serialUSB sends bad messages.

Hardware Arduino Due
1

Hi all,
I've had this problem for a few months now and haven't been able to figure it out. Every once and a while my Arduino Due sends data out in the wrong order over SerialUSB (native USB -> SAM3X). I have seen this when compiling with Arduino 1.5.2 and Arduino 1.5.6-r2.
To try to catch the problem I have reduced the code to this sample sketch:

/*
    ArduinoDue SerialUSB bug test
*/

long counter = 0;

void setup() {
  while(!SerialUSB);      // wait for the serialUSB to come up
  delay(100);
  SerialUSB.println("Arduino DUE SerialUSB (SAM3X native USB)");
  SerialUSB.println("This demonstrates how SerialUSB sends messages in the wrong order sometimes");
  SerialUSB.println("Just start the Arduino serial monitor while this sketch runs on an Arduino DUE");
  SerialUSB.println("If the serial messages arrive correctly, just close and open the serial monitor again");
  SerialUSB.println("After a few iterations you'll see the messages get mixed up");
  SerialUSB.println(" --- ");
  SerialUSB.println("Tested with Arduino 1.5.6-r2");
}

void loop() { 
  if(SerialUSB){
      counter ++;
     SerialUSB.print(counter);
     SerialUSB.print(" - I have sent ");
     SerialUSB.print(counter);
     SerialUSB.println(" messages so far.");
     delay(200);
  }
}

After uploading this to the Arduino Due I just open the Serial Monitor. The expected feedback is something like this:

61 - I have sent 61 messages so far.
62 - I have sent 62 messages so far.
63 - I have sent 63 messages so far.
64 - I have sent 64 messages so far.
65 - I have sent 65 messages so far.
66 - I have sent 66 messages so far.
67 - I have sent 67 messages so far.

But when i restart the serial monitor I sometimes get something like this:

m - I have sent 16 messages so far.
17 - I have sent 17 messages so far.
18 - I have sent 18 messages so far.
 m - I have sent 19 messages so far.
20 - I have sent 20 messages so far.
21 - I have sent 21 messages so far.
 m - I have sent 22 messages so far.

or

16 - I have sent 16 messages so far.
17 - I have sent  m messages so far.
18 - I have sent 18 messages so far.
19 - I have sent 19 messages so far.
20 - I have sent  m messages so far.
21 - I have sent 21 messages so far.
22 - I have sent 22 messages so far.

The problem sometimes happens right from the start, without re-starting the serial connection.
I have created an OpenFrameworks app that feeds me back the serial messages and see the same problem appear, so it's not related to the Arduino IDE
I have tried different BAUD rates, and have seen it every time.
I have tested this with different Arduino Due (all R3) boards, they all do it.

Does this ring a bell for anyone? I'm out of ideas..

2

The problem seems to appear less often when adding a bit of delay after every SerialUSB.print() and SerialUSB.println() call. for example:

SerialUSB.println("hello");
delayMicroseconds(500);

I'm still curious about the reason why this problem shows itself sometimes and other times not at all..
Maybe it has something to do with this:

As of version 1.0, serial transmission is asynchronous; Serial.print() will return before any characters are transmitted.

from

3

Not saying the problem doesn't exist, but I could not replicate it on this system:

OS Name:    Microsoft Windows 7 Professional (32-bit)
Version:	 6.1.7601 Service Pack 1 Build 7601
Board:      Arduino Due R3
Connection: 3ft USB cable, direct connect to PC USB port (no external hub).
Tests:      Open/closed/checked serial monitor 10 times.
Final results:
[IMG]http://i60.tinypic.com/dbt6i8.jpg[/img]
4

ah that's interesting! I can more or less reproduce the problem consistently.
I forgot to mention I'm on OSX 10.9.3, also no external hub.
I hadn't considered the OS might be the problem.