A real‐time Java tool chain for resource constrained platforms

Abstract

The Java programming language was originally developed for embedded systems, but the resource requirements of previous and current Java implementations -especially memory consumption -tend to exclude them from being used on a significant class of resource constrained embedded platforms. The contribution of this paper is an architecture and implementation of a Java execution stack for resource constrained embedded platforms with a few kB of RAM and flash memory. The resource requirements of the presented architecture has been reduced significantly through all the layers of the architecture by integrating the following: (1) a lean virtual machine without any external dependencies on POSIX-like libraries or other OS functionalities; (2) a hardware abstraction layer, implemented almost entirely in Java through the use of hardware objects, first level interrupt handlers, and native variables; and (3) an implementation of the Safety-Critical Java profile Level 0 and 1 for hard real-time applications. All Java components of a given application are minimized through program specialization, and because (2) and (3) are written in Java, the program specialization has a significant impact on the resulting program size. An evaluation of the presented solution shows that the miniCDj benchmark gets reduced to a size where it can run on resource constrained platforms.A RT-JAVA TOOL CHAIN FOR RESOURCE CONSTRAINED PLATFORMS 2409 avoid programmer defined native functions. This architecture was proposed in [7]. hardware objects and interrupt handlers are adopted from that proposal. These core concepts are here supplemented with the following:A Process concept as defined in Modula 2 [8]. On top of this single concept a variety of scheduling mechanisms can be built to support, for example, the standard Java Thread class or SCJ handlers. A Monitor concept that can be attached to an object for synchronization coordinated with process scheduling. A Memory Area concept that allows the Java application to control the allocation and reclamation of runtime data. On top of this concept, memory management features can be built to support, for example, the SCJ memory model. A Clock concept that specifies methods to get the granularity and the absolute time. This concept supports scheduling of tasks as defined by the SCJ profile.To support real-time capabilities, a standalone version of the SCJ profile Levels 0 and 1 has been implemented. The SCJ infrastructure is built exclusively in Java on top of the HAL.Using features of the underlying VM, most notably (1) program specialization and (2) aheadof-time compilation combined with interpretation, the solution supports efficient execution of high dependability applications on resource constrained platforms. In summary, the contribution of this paper is an integrated tool chain for the execution of real-time Java software components on resource constrained embedded platforms with a few kB of RAM and flash. This is achieved by combining the following:A Java HAL supporting hardware objects, interrupt ...

Conformance test development with the Java modeling language

“…In checking the feasibility of doing this, the developed tests are executed using the HVM, which is a VM designed for resource-constrained embedded platforms with a few kilobyte of RAM and flash memory [6,9]. It follows that the tests should execute on resource-constrained devices and not use standard PC host environments.…”

“…In our case, we have followed the development of the SCJ specification closely, commented on intermediate draft specifications and, over the years, acquired considerable insight in the details of the specification, as we have developed several prototype implementations [4][5][6]; the most recent one includes all three SCJ levels [7,8].This implementation is developed for resource-constrained embedded platforms, specifically the hardware-near virtual machine (HVM) [9]. This paper presents a model-based development of a Technology Compatibility Kit test suite and a test execution tool for the draft safety-critical Java profile specification.…”

Certifiable Java for Embedded Systems

“…Within the CJ4ES project we developed and used two different Java virtual machines: (1) the JOP processor [36] as a hardware implementation in an FPGA, and (2) the hardware near virtual machine [14] as a software VM targeting small embedded processors with small memory constraints.…”

“…The Hardware near Virtual Machine (HVM) [14] is a low footprint software VM intended for resource constrained platforms. It is a Java-to-C compiler, but supports interpretation as well, and a mix of the two execution styles.…”

“…The SCJ implementation on top of HVM [14,45] has the architecture, shown in Figure 1, with a minimal hardware interface layer specified in the vm Interface.…”