PreonVM – Java VM for embedded systems

The PreonVM is a virtual machine (VM) from VIRTENIO for use in embedded systems with very low resources such as the radio module Preon32 from VIRTENIO. The virtual machine is highly optimized, requires no additional operating system and runs directly on the microcontroller. This approach makes it possible to use applications in Java via a transformation process for the radio module Preon32. In this context, VIRTENIO offers corresponding software libraries for various interfaces. This makes the programming of applications that record sensor data and actuator controls elegantly possible. In addition, the radio interface for IEEE802.15.4 and AES encryption in hardware are mentioned as innovative components that are easy to use in the virtual machine.

Embedded systems with minimal resources have so far been programmed in special and less comfortable languages. Complex applications are therefore time-consuming and have a high error potential. The VIRTENIO approach brings the convenience, language complexity and security of a virtual machine combined with an object-oriented programming language into the world of embedded systems. VIRTENIO currently offers the virtual machine as innovative operating software for its radio module Preon32 for wireless networks according to IEEE 802.15.4.

At the same time, the development process of the hardware and the application program are decoupled. The application program is developed against a virtual architecture with corresponding interfaces, which remains unchanged over time.

In addition, the virtual machine has been optimized in such a way that applications can be run on an 8/32-bit microcontroller with at least 8 KB RAM and at least 128 KB Flash. The complete virtual machine with peripheral connection such as the radio transceiver according to IEEE 802.15.4 therefore requires less than 60KByte Flash memory.

The virtual machine developed by Virtenio is used as operating software on the wireless sensor node type “Preon32”. With this operating software it is possible that applications written as source code in Java can be used on the Preon32 after you have gone through the following transformation process.

In the simplest case, all components of the application must first be available as Java source code or Jar archives. The Java compiler then translates them into Java byte code, which creates a class files with the file extension “.class”. The Java class files contain the methods of the class and a lot of additional information, which, however, also occupies additional memory space. This is only required to a very limited extent in the wireless sensor node. For this reason, the next necessary step is to reduce information and bundle Java Class files using the VIRTENIO ClassLinker to a single file with the extension “.vmm”. This contains all information required for program execution on the virtual machine in the sensor node. The file size of the “.vmm” is significantly smaller than the sum of the individual Java class files due to appropriate procedures. The “.vmm” can be loaded into the sensor node and executed there.

In order to provide the developer with an ideal starting point for complex applications in distributed embedded systems such as wireless networks, the virtual machine was supplemented by many software components. With this prerequisite, applications can be quickly assembled as if from a modular system. Own software parts from existing Java applications for the desktop can be integrated without adaptation of the source data. With the familiar development tools for Java, applications for wireless sensor networks can now be implemented.