COMPARATIVE ANALYSIS OF EPICS IOC AND MARTe FOR THE DEVELOPMENT OF A HARD REAL-TIME CONTROL APPLICATION ∗

EPICS is used worldwide to build distributed control systems for scientific experiments. The EPICS software suite is based around the Channel Access (CA) network protocol that allows the communication of different EPICS clients and servers in a distributed architecture. Servers are called Input/Output Controllers (IOCs) and perform real- world I/O or local control tasks. EPICS IOCs were origi- nally designed for VxWorks to meet the demanding real- time requirements of control algorithms and have lately been ported to different operating systems. The MARTe framework has recently been adopted to de- velop an increasing number of hard real-time systems in different fusion experiments. MARTe is a software library that allows the rapid and modular development of stand- alone hard real-time control applications on different oper- ating systems. MARTe has been created to be portable and during the last years it has evolved to follow the multi-core evolution. In this paper we review several implementation differ- ences between EPICS IOC and MARTe. We dissect their internal data structures and synchronization mechanisms to understand what happens behind the scenes. Differences in the component based approach and in the concurrent model of computation in EPICS IOC and MARTe are explained. Such differences lead to distinct time models in the com- putational blocks and distinct real-time capabilities of the two frameworks that a developer must be aware of.