Modernizing the FASTBUS readout system of the CERN NA49/NA61 experiment ToF detector using Raspberry Pi

Abstract

The FASTBUS [1] crate is a powerful modular data transfer system which uses ECL (Emitter Coupled Logic) electrical standards to achieve fast parallel communications with a 32 bits wide data line. Although FASTBUS crates were largely replaced by modern serial solutions [2][3], they are still in widespread use in legacy systems such as in older particle detectors. In this study we present a modernized FASTBUS readout system designed in collaboration with the Institute of Physics and Astronomy at Eötvös Lor ́and University for use with the ToF (time of flight) detector[4] formerly used in the CERN NA49/NA61 experiments and now being recommissioned for educational and research purposes. Our goal was to design a low-cost system capable of reading out up to 744 data channels used in the detector. For these purposes we have decided to use a Raspberry Pi 3B microcomputer connected to the FASTBUS crate via a custom control card. The control card translates between ECL and TTL signals and extends the number of general purpose I/Os of the Raspberry Pi, so it can use almost all FASTBUS operations.