Front-End Control and Monitoring System for the Resistive Plate Chambers at the CMS Experiment

The Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) uses Resistive Plate Chambers (RPCs) as a trigger-dedicated muon detector. The RPC subdetector presently consists of 912 chambers, providing a $\approx$~3\,ns time resolution for the pseudorapidity region $\lvert\eta\rvert~<~1.6$. \\ Up to 18 on-detector Front-End Boards (FEBs) per RPC are responsible for signal processing. Each FEB is configured and monitored through its Inter-Integrated Circuit (I$^2$C) interface to ensure correct and safe detector operation. The resulting $\sim$1.2\,k I$^2$C lines, serving 3 to 6 FEBs apiece, are accessible through Control Boards (CBs) in token rings. \\ An online control and monitoring system has recently been developed to automatically configure and continuously monitor FEB parameters. A fine-grained software model of hardware and detector components, organized in a dual hierarchical tree structure, facilitates command and data flow. A novel web-based user-interface allows control of and navigation through the system for efficient problem tracing. \\ This paper covers the front-end control and monitoring system for the RPC subdetector; the online software components that allow for flexible configuration and comprehensive monitoring are described.