CANbus protocol and applications for STAR TOF control

A large-area Time-of-Flight (TOF) system based on Multi-gap Resistive Plate Chambers (MRPCs) has recently been installed in the STAR experiment at RHIC. The approximately 23000 detector channels are read out and digitized using custom electronics based on the CERN NINO and HPTDC chips. The data are sent to the experimental data acquisition system (DAQ) using the ALICE fiber optics based Detector Data Link (DDL). The readout system consists of a total of approximately 2100 custom electronics boards mounted directly on 120 TOF trays, as well as four DAQ and trigger interface boards outside the detector that collect data from 30 trays each and send it to DAQ. Control and monitoring of these electronics boards is done using a tiered network of CANbus connections to a control PC. We describe the physical implementation and topology of the CANbus connections and the custom protocol developed for this project. Several command-line tools as well as a Qt4-based graphical tool developed on the host side to facilitate configuration, control, and monitoring of the TOF system are also described.