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We present an approach of two-level deployment process for component models used in distributed real-time embedded systems to achieve predictable integration of real-time components. Our main emphasis is on the new concept of virtual node with the use of a hierarchical scheduling technique. Virtual nodes are used as means to achieve predictable integration of software components with real-time requirements. The hierarchical scheduling framework is used to achieve temporal isolation between components (or sets of components). Our approach permits detailed analysis, e.g., with respect to timing, of virtual nodes and this analysis is also reusable with the reuse of virtual nodes. Hence virtual node preserves real-time properties across reuse and integration in different contexts.

This paper presents the implementation of a HierarchicalScheduling Framework (HSF) on an open sourcereal-time operating system (FreeRTOS) to support the temporalisolation between a number of applications, on a single processor.The goal is to achieve predictable integration and reusability ofindependently developed components or applications. We presentthe initial results of the HSF implementation by running it onan AVR 32-bit board EVK1100.

The paper addresses the fixed-priority preemptive schedulingat both global and local scheduling levels. It describes the detaileddesign of HSF with the emphasis of doing minimal changes tothe underlying FreeRTOS kernel and keeping its API intact.Finally it provides (and compares) the results for the performancemeasures of idling and deferrable servers with respect to theoverhead of the implementation.

This paper presents extensions to the previous implementationof two-level Hierarchical Scheduling Framework(HSF) for FreeRTOS. The results presented here allow the useof HSF for FreeRTOS in hard-real time applications, with thepossibility to include legacy applications and components notexplicitly developed for hard real-time or the HSF.

Specifically, we present the implementations of (i) global andlocal resource sharing using the Hierarchical Stack ResourcePolicy and Stack Resource Policy respectively, (ii) kernel supportfor the periodic task model, and (iii) mapping of original FreeRTOSAPI to the extended FreeRTOS HSF API. We also presentevaluations of overheads and behavior for different alternativeimplementations of HSRP with overrun from experiments on theAVR 32-bit board EVK1100. In addition, real-time schedulinganalysis with models of the overheads of our implementation ispresented.

We present the concept of runnable virtual nodes as a means to achieve predictable integration and reuse of software components in cyber-physical systems. A runnable virtual nodeis a coarse-grained real-time component that provides functional and temporal isolation with respect to its environment.Its interaction with the environment is bounded both by a functional and a temporal interface, and the validity of itsinternal temporal behavior is preserved when integrated with other components or when reused in a new environment.Our realization of runnable virtual nodes exploits the latest techniques for hierarchical scheduling to achieve temporalisolation, and the principles from component-based software-engineering to achieve functional isolation. In the paperwe present a proof-of-concept case study, implemented in the ProCom component-technology executing on top of FreeRTOSbased hierarchical scheduling framework.