CompactPCI/Linux platform for medium level control system on FTU

In large fusion experiments, such as tokamak devices, there are common trends for slow control systems. Because of complexity of the plants, several tokamaks adopt the so-called ‘standard model’ (SM) based on a three levels hierarchical control: (i) high level control (HLC)—the supervisor; (ii) medium level control (MLC)—I/O field equipments interface and concentration units and (iii) low level control (LLC)—the programmable logic controllers (PLC). FTU control system was designed with SM concepts and, in its 15 years life cycle, it underwent several developments. The latest evolution was mandatory, due to the obsolescence of the MLC CPUs, based on VME/Motorola 68030 with OS9 operating system. Therefore, we had to look for cost-effective solutions and we chose a CompactPCI-Intel x86 platform with Linux operating system. A software porting has been done taking into account the differences between OS9 and Linux operating system in terms of inter/network processes communications and I/O multi-ports serial driver. This paper describes the hardware/software architecture of the new MLC system emphasising the reliability and the low costs of the open source solutions. Moreover, the huge amount of software packages available in open source environment will assure a less painful maintenance, and will open the way to further improvements of the system itself.