INTERFACING CANBUS TO EPICS AT THE SWISS LIGHT SOURCE
M. Dach, T. Korhonen, T. Pal · 2003
The SLS accelerator control system is based on EPICS and uses VME crates as control units. In order to monitor the VME crates the CANbus system has been introduced. The challenge was to interface CANbus into EPICS using PC, running Real-Time Linux, and the CAN Open protocol. This paper describes the hardware and software structure of CANbus system in the context of the RealTime requirements. Several approaches to optimize the deterministic behavior of such a system in LINUX-RT (RTAI - Real Time Application Interface) and EPICS environment are discussed. MISSION STATEMENT The aim of the work behind this paper was to design and implement a Supervisory Control and Diagnostic System (SCDS) to monitor VME crates of the control system of the Swiss Light Source (SLS) at the Paul Scherrer Institute. For the operation of the SLS facility a distributed control system based on EPICS [1] (Experimental Physics and Industrial Control System) infrastructure is used. This system uses VME as operational nodes, and PC/Linux as client platforms. The local Ethernet network links all components of the system. During the commissioning phase of the accelerators, a problem emerged related to VME failures. This refers rather to the software implementation than to the hardware. The SLS control system includes approximately 166 VME crates distributed around the accelerator rings. The hang up status of certain operational VME nodes requires immediate operator intervention. In most cases rebooting the faulty node was necessary. A desirable solution to fulfill this requirement would be the installation of SCDS to monitor and control the VME nodes.