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Topics and trends related to the Java ecosystem with occasional random rants.

  • May 18, 2017

Updates to Java Serial Communications, Raspberry Pi 3

James Connors
Principal Solutions Consultant

Why not kill a few birds with one stone?  First, it was high time to finally learn how to post an article with our new blogging platform (based on Oracle Content Marketing).  Second, and this is of course relative to my little world, it would be useful to provide an update to one of my more historically read topics dealing with serial communications and Java.

A recent comment to one of the Java Serial Port Communications posts mentions difficulty with using the provided RxTx shared object for the ARMv7l architecture.  So I figured I'd rebuild it taking advantage of some new hardware. The Raspberry Pi 3 represents the first 64-bit ARM offering from the Raspberry Pi Foundation, and can be ultimately utilized to build both 32 and 64-bit binaries.  Although currently most work on this device is done in 32-bit mode, there are some 64-bit environments available.  For the 32-bit ARMv7l environment we'll use the ubiquitous Raspbian Jessie distribution. And for our 64-bit AArch64 instance we'll use OpenSuSE LEAP 42.2.

To understand the history of this topic, you can take a look at the following past posts:

RxTx code has not always been readily available, so to improve upon that, you can now go to https://github.com/jtconnors/rxtx-2.1-7r2 and pull down the source (including the modifications needed to build for Java versions 6 though 8).  Additionally, another repository has been created at https://github.com/jtconnors/rxtx-2.1-7r2-binaries to keep compiled binaries for the native shared objects associated with RxTx for popular embedded platforms.  If you create subsequent binaries for additional platforms, I'd be glad to add them.

Finally, while playing around with both 32 and 64-bit variants, I thought it might be useful to run the SPECjvm2008 benchmark to see how Java performance differs between the architectures.  One of the primary advantages of a 64-bit JVM is its ability to support much larger heap sizes.  The usefulness of a 64-bit JVM on a Raspberry Pi 3 is certainly debatable, considering it only has 1GB of RAM, nonetheless it would be interesting to see what overhead might be incurred using the 64-bit JVM.

Although results of individual components of the benchmark do vary, overall it looks like the 64-bit JVM does incur some (hopefully acceptable) overhead.

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