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What is MSCB?

Physics experiments need to control equipment commonly grouped under slow control: high-voltage supplies, temperatures, pressures, power rails, relays, and similar quantities. General-purpose interfaces such as IEEE-488 and RS-232 can do this, while full industrial field buses can require substantial integration effort.

The Midas Slow Control Bus (MSCB) was developed at PSI by R. Schmidt and S. Ritt as a deliberately compact alternative. It provides fewer mechanisms than a general industrial field bus, but it is inexpensive, optimized for experimental environments, and usable either with the MIDAS data acquisition system or independently.

Design goals

  • inexpensive nodes built around microcontrollers with integrated ADCs, DACs, and digital I/O;
  • robust differential signaling over RS-485;
  • enough address space for large detector systems;
  • discoverable, typed node variables so clients need little device-specific knowledge;
  • individual, group, and broadcast operations;
  • deterministic node-side response behavior; and
  • a small host library and interactive command-line tool.

Implementation

The repository still contains firmware for many MSCB devices and the C library, but the recommended host connection is an Ethernet submaster. The repository also includes a Python implementation that speaks the same UDP protocol without loading a compiled library.