The pilot deployments of the new WRT (White-Rabbit-based Timing) system are progressing successfully and delivering excellent results!

In a retrospective meeting held last week, marking one year since the first pilot deployments, users expressed high satisfaction with both the product and the support provided. The outcome highlights a strong example of effective multi-group collaboration.

The new WRT system will replace the aging GMT (General Machine Timing) and BST (Beam Synchronous Timing) infrastructure, which has served CERN for over 20 years.

In the HL-LHC era, thousands of CTR (Central Timing Receiver) boards and dozens of BOBR (BST Observation Receiver) boards will be replaced by WREN (White Rabbit Event Node) boards, marking the largest WR installation at CERN to date.

The WREN is a general-purpose WRT node capable of functioning as a GMT receiver, GMT transmitter, BST receiver, or BST transmitter. Its design combines gateware on the FPGA fabric (HDL) with firmware on the SoC’s hard CPUs. Time-critical functions, such as RF reconstruction for BST and precise trigger generation, are handled in gateware, while less time-critical tasks, frame parsing, configuration, and diagnostics, run in bare-metal code on the Arm Cortex-R5F. The Arm Cortex-A53 cores remain unused for now, providing flexibility for future developments (e.g. WREN as a stand-alone node).

So far, approximately 50 WRENs have been deployed across labs, LINAC3, LEIR, SM18, and the FAIR facility, where since a year of operation they have successfully taken over from the CTR system.

This is a collaborative effort involving teams from CEM, CSS, BI and EN/EL working together on this multi-M CHF project. The WREN hardware is open-source, designed using KiCad, reviewed through the HARP process, and continuously improved during this pilot phase thanks to valuable feedback from all main Equipment Groups (ABT, BI, EPC, MPE, RF).