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Midas Slow Control Bus

MSCB is a compact, self-documenting field bus for experiment slow control. It connects a PC through a submaster to RS-485 nodes that expose typed variables for measurements, demand values, configuration, and diagnostics.

  • Understand the bus

    Learn the addressing model, node variables, submasters, and RS-485 topology.

    Architecture

  • Implement the protocol

    Use the byte-level command, response, CRC, timing, and UDP transport specifications.

    Protocol

  • Operate a network

    Discover submasters, scan nodes, inspect variables, save configurations, and upgrade firmware.

    Getting started

  • Build applications

    Consult the C, C++, and Python APIs, status codes, and complete msc command reference.

    API reference

Documentation scope

This site documents the MSCB bus and the current repository:

  • the complete protocol tables, including command encoding, responses, variable metadata, units, and timing;
  • Ethernet submaster UDP framing and authentication derived from the current implementation;
  • current C, C++, and Python usage;
  • a function-by-function reference for src/mscb.cxx; and
  • a command reference derived from src/msc.cxx.

At a glance

Property Value
Physical node bus Half-duplex RS-485
Address space 16-bit node and group addresses
Nodes per address space Up to 65,536
Direct nodes per 1/8-load segment Up to 256
Variables per node Up to 256, indexed 0–255
Current protocol version 5
Ethernet submaster transport UDP, default port 1177
Data integrity CRC-8, polynomial x⁸ + x⁵ + x⁴ + 1