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17 Oct 2010, 09:30
Sven Riedel (8 posts)

I just had a bit of trouble getting Processing and Arduino accessing the serial port at the same time: Processing raised an exception trying to access the serial port because a lock file existed. Turns out that you can’t have arduinos serial monitor and processing accessing the serial port at the same time.

If you get that exception, turn off arduinos serial monitor and try running the Processing sketch again.

I didn’t see a note regarding this in the chapter (which may be due to lack-of-caffeine-induced selective blindness :) ), but a footnote regarding this would probably be helpful to other people running into this problem, as the cause of the exception isn’t immediately clear.

17 Oct 2010, 15:38
Maik Schmidt (120 posts)

Hi Sven!

(which may be due to lack-of-caffeine-induced selective blindness :) This has nothing to do with it, so you can safely go an grab another cup of coffee :-)

The last beta actually did not contain such a hint. I have added one already and I think the next version of the book will even contain twice.

Best, Maik

02 Sep 2011, 00:49
mkaberline (1 post)

I ran into an issue while attempting to communicate between the processing application and the arduino via the serial port. I received the following warning: RxTx Version mismatch. JAR version = RxTx2.2pres Native Lib.version = RxTx-2.2pres.

??? I know what it means, but I’m not sure how serious the problem is or what I can do to rectify the situation. Can anyone help??

02 Sep 2011, 04:57
Maik Schmidt (120 posts)

The warning looks a bit strange, because regarding the version number the JAR version and the Native Lib version seem to match. They are both 2.2pres.

Does the communicaton work?

03 Jan 2012, 09:35
Misery (1 post)

OH yes,Sven. I just have the same problem. Thank you.

24 Jun 2012, 20:04
Jim Puls (4 posts)

This is the warning I received:

WARNING: RXTX Version mismatch Jar version = RXTX-2.2pre1 native lib Version = RXTX-2.2pre2

It doesn’t seem to stop things from working. Doing a Google search, others have gotten the same warning in other contexts, but the “cure” seems to be a bit involved for one starting up in a tutorial.

Also, it was not self evident to me that PreciseSensor needed to be running first, before starting InvertedSonar. The error in this case was:

ArrayIndexOutOfBoundsException: 0 at InvertedSonar.setup(

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