Road to solve the delay on the Arduino IDE

Devs: please include this update in Arduino 0018. The enhanced rxtx solves one of the most annoying problems I’ve run into in the Arduino IDE. If you have any sleeping Bluetooth SPP devices, the default Arduino IDE will take a long time to load, and then a long time to open the Tools menu every time.

In addition, your sleeping Bluetooth SPP connections are trashed. The old rxtx somehow sits on them and prevents them from being used by other applications. Just by opening the Arduino IDE once, you now have to reset multiple Bluetooth devices, or unpair/repair them.

The new rxtx dll above fixes that issue completely.

is this a all windows thing or exclusive to vista + (wondering cause i have it on both xp 32 bit and xp 64 bit and its been working fine)

If you don’t have bluetooth serial devices then you probably aren’t going to notice anything.

Yes, yes, yes, please add this to 0018! The difference is dramatic! My startup goes from a little below 1 minute to only several seconds. Opening the tools menu even took me two minutes (no joke) and now it shows immediately.

(Thanks to the OP) [smiley=thumbsup.gif] [smiley=thumbsup.gif] [smiley=thumbsup.gif]

Hello togheter,

I have also problems with my arduino17 on a vista pc. I would try this fix, but cannot open the rar file. Can anybody give me a hint, how to open this file, Thank's


I would try this fix, but cannot open the rar file. Can anybody give me a hint, how to open this file

Also, from

Third party programs that can only read (unpack) RAR files include: WinZip (Windows), 7-Zip (multiplatform), IZArc (Windows), PeaZip (Windows, Linux), Zipeg (Windows, Mac OS X), ALZip (Windows), along with the free version of unrar (which is available for Linux and FreeBSD). Mac OS X readers include Stuffit Expander, The Unarchiver and Zipeg. Stuffit Expander is also available for Mac OS Classic with RAR support for this platform.

If you go to the second link above, all those third party programs have their own links. I'm too lazy on a Saturday to copy the links into this reply. ;)

My fixed dll is still working with the version 0018 :) and of course for those who asked, with the 0017 too. ;D

Another big thanks for fixing this problem. I have an older laptop running XP, and the arduino application was completely unusable due to the delays in the 0018 distribution DLL.

Your modified DLL fixed the entire problem, instantly. 8-)


Dear eried,

Please could I have the source code to your modified version of the rxtx library?



I will try to look for it. But you can build your own patched version. First look the point 7 of this document, ignore the text, just copy the "serial_test" function code.

Then get the full source from

And finally, replace the code and Compile.

Works for me using Arduino 0019!

Thank you so much, eried! You’ve done us all a great favor! Nice work!

Yet another very happy user, thanks a lot!

The fix - It works with Processing too, btw.

I am trying to get a link to this fix included in the

.. I hope this will be possible. I remembered seeing this solution long time ago, but I had trouble refinding it.

More links to this genious :-)

with humble respect Christian Liljedahl

I have same problem.
This is very fantastic solution.

Many thanks!!!

Hey all, i just got my UNO yesterday and noticed the delay on the IDE soft and i can tell that this fix worked for the 0021, too(i had BT com port working on my laptop). thanks! :)

This helped me a lot!!! Thank you very much!!!

//Arduino UNO - 021 - Win7

gracias por el archivo! ha mejorado la respuesta del programa muy mucho!

thanks for the great job done! I had the same problem in Processing (as they share the same platform) and also solved it.

:) Luckily I found this thread.

Eried, thank you for this fix; extremely helpful. Turned an almost unusable program into a valuable tool.

works as well with Arduino 022.



Hello Mr ERied.

I have the same problem with the slow Arduino IDE. I'm new at this and don't yet know Java. When I look at the Arduino\Lib directory there are only *.jar files. I do not know what to do with your *.rar file. Could you please give more detailed instructions for us Java newbies. Gracias in advance. Flav

My bad. I downloaded 7-zip to unzip your *rar file and replaced the rxtxSerial.dll iin the Arduino directory. However, there seems to be no change in the excessive compile time using the arduino IDE. I am using windows 8.1. Any thoughts and suggestions? Flav

In addition to using Mr. Ried's solution, I had to turn off Spybot's live protection. Now all is well!! Thank you again Mr. E. Ried!!