secs-gem

A C++20 SECS-II / HSMS / GEM client and server, fully containerised, with every behavioural rule encoded as YAML data (control state, equipment data dictionary, SECS-II message shapes).

See COMPLIANCE.md for the per-capability E5/E30/E37 audit. Every GEM Fundamental and every GEM Additional capability that E30 binds to a concrete SECS-II message set is implemented and round-trip-tested.

Quick start

Everything runs in Docker — no compiler or build tools on the host.

docker compose run --rm builder     # configure + compile
docker compose run --rm tests       # 84+ test cases / 480+ assertions
docker compose up --no-deps server client   # live two-container demo

Architecture

The project is "spec-as-data": the SEMI behavioural rules live in YAML; the C++ is the engine that reads them.

   ┌──────────────────────────────────────────────────────────────┐
   │ data/                                                        │
   │   messages.yaml       SECS-II message catalog (44 SxFy)      │
   │   control_state.yaml  E30 §6.2 transition table              │
   │   equipment.yaml      SVIDs / DVIDs / ECIDs / CEIDs /        │
   │                       alarms / recipes / commands /          │
   │                       capabilities / spool / DVID list       │
   └──────────────────────┬───────────────────────────────────────┘
                          │  (loaded at startup, codegened at build)
                          ▼
   ┌──────────────────────────────────────────────────────────────┐
   │ tools/gen_messages.py                                        │
   │   reads messages.yaml -> emits generated/secsgem/gem/messages.hpp
   └──────────────────────┬───────────────────────────────────────┘
                          │
                          ▼
   ┌──────────────────────────────────────────────────────────────┐
   │ apps/                                                        │
   │   secs_server.cpp     passive equipment                      │
   │   secs_client.cpp     active host                            │
   │                       (both use gem::Router for dispatch)    │
   └────────────┬───────────────────────────┬─────────────────────┘
                │                           │
                ▼                           ▼
   ┌──────────────────────────────────────────────────────────────┐
   │ secsgem::config   loader.hpp: YAML -> tables + data model    │
   │ secsgem::gem      ControlTransitionTable + ControlStateMachine,│
   │                   EquipmentDataModel composing nine stores:  │
   │                     SVID, DVID, ECID, Event Subscriptions,   │
   │                     Alarms, Recipes, Clock, Commands, Spool, │
   │                     Limits, Traces                           │
   │                   Router (stream, function) -> handler       │
   │                   generated messages.hpp (all 44 SxFy)       │
   │ secsgem::hsms     Connection (Asio), Header, Frame, Timers   │
   │                   Auto-emits S9F3/F5/F7/F9/F11 on protocol   │
   │                   error conditions.                          │
   │ secsgem::secs2    Item (variant), encode/decode, Message     │
   └──────────────────────────────────────────────────────────────┘

Tree

secs-gem/
├── Dockerfile, docker-compose.yml      # toolchain + demo
├── CMakeLists.txt
├── implementation_plan.md              # 7-layer spec-as-data roadmap
├── COMPLIANCE.md                       # per-capability E5/E30/E37 audit
├── data/
│   ├── messages.yaml                   # SECS-II message catalog
│   ├── control_state.yaml              # E30 control state transitions
│   └── equipment.yaml                  # equipment data dictionary
├── tools/
│   └── gen_messages.py                 # codegen (messages.yaml -> .hpp)
├── include/secsgem/
│   ├── secs2/{item,codec,message}.hpp
│   ├── hsms/{header,connection}.hpp
│   ├── gem/{control_state,data_model,messages_helpers,router}.hpp
│   ├── gem/store/                      # one file per focused store:
│   │   ├── status_variables.hpp        # SVIDs + DVIDs
│   │   ├── equipment_constants.hpp     # ECIDs + EAC range validation
│   │   ├── event_reports.hpp           # CEIDs + Reports + Links
│   │   ├── alarms.hpp                  # alarm registry
│   │   ├── recipes.hpp                 # process program store
│   │   ├── clock.hpp                   # 16-char TIME with offset
│   │   ├── host_commands.hpp           # RCMD registry
│   │   ├── spool.hpp                   # spool queue + state
│   │   ├── limits.hpp                  # variable limit definitions
│   │   └── trace.hpp                   # active trace configs
│   ├── config/loader.hpp
│   └── endpoint.hpp
├── src/{secs2,hsms,gem,config}/*.cpp + endpoint.cpp
├── apps/{secs_server,secs_client}.cpp
└── tests/test_*.cpp

Adding a capability

The point of "spec-as-data" is that adding behaviour almost never requires a C++ change.

Add a new SVID

# data/equipment.yaml
svids:
  - {id: 4, name: ChamberTemp, units: "C", type: U4, value: 25}

Restart the server. The host sees the new SVID via S1F11/F3 immediately.

Add a new host command with side effects

# data/equipment.yaml
host_commands:
  - {name: VENT, ack: Accept, emit_ceid: 400, set_alarm: 2}

Add a new state transition

# data/control_state.yaml
transitions:
  - {from: OnlineRemote, on: host_request_offline, to: EquipmentOffline, ack: Accept}

Add a new SECS-II message

# data/messages.yaml
- id: S6F30
  stream: 6
  function: 30
  w: true
  builder: s6f30_something
  parser: parse_s6f30
  body:
    kind: list
    struct_name: Something
    fields:
      - {name: field_a, shape: {kind: scalar, item_type: U4}}
      - {name: field_b, shape: {kind: scalar, item_type: ASCII}}

docker compose run --rm builder regenerates messages.hpp. The typed builder, parser, and struct definition appear automatically.

Demo

The two-container demo walks ~20 SECS transactions:

[host]  -> Select.req                  [equip] <- Select.req
[host]  == SELECTED ==                 [equip] == SELECTED ==
[host]  -> S1F13 W                     [equip] -> S1F14 (COMMACK=0)
[host]  -> S1F17 W                     [equip] HostOffline -> AttemptOnline -> OnlineRemote
[host]  -> S1F19 W                     [equip] -> S1F20 (12 capabilities)
[host]    CCODE 1 Establish Communications
[host]    CCODE 2 Dynamic Event Report Configuration
[host]    ...
[host]    CCODE 14 Spooling
[host]  -> S1F21 W                     [equip] -> S1F22 (2 DVIDs)
[host]  -> S1F11 W                     [equip] -> S1F12 (3 SVIDs)
[host]  -> S1F3 W                      [equip] -> S1F4
[host]  -> S2F29 W                     [equip] -> S2F30 (2 EC entries)
[host]  -> S2F33/F35/F37 W             [equip] subscribes CEIDs 200, 300
[host]  -> S2F41 W START               [equip] emit S6F11 CEID=300
[host]    EVENT CEID=300 (1 reports)
[host]  -> S5F5 W                      [equip] -> S5F6 (2 alarms)
[host]  -> S5F3 W                      [equip] enables alarm 1
[host]  -> S2F41 W FAULT               [equip] emit S5F1 + S6F11 CEID=200
[host]    ALARM SET ALID=1 cat=4 "Chiller Temp High"
[host]  -> S2F41 W SPOOL_ON            [equip] force_spool=true
[host]  -> S2F41 W START                       spool: S6F11 CEID=300 queued
[host]  -> S2F41 W SPOOL_OFF           [equip] force_spool=false (depth=1)
[host]  -> S6F23 W Transmit            [equip] drains 1 spooled message
[host]    EVENT CEID=300                       (from spool, post-fact)
[host]  -> S7F19 W                     [equip] -> S7F20 (2 PPIDs)
[host]  -> S7F5 W RECIPE-A             [equip] -> S7F6
[host]  -> S10F1 W                     [equip] TERMINAL[0] Hello equipment!
[host]  -> S1F15 W                     [equip] OnlineRemote -> HostOffline
[host]  -> Separate.req                [equip] <- Separate.req

Build details

The toolchain image (Dockerfile) is Ubuntu 24.04 with g++-13, CMake, Ninja, libasio-dev, libyaml-cpp-dev, and Python 3 for the codegen. doctest is fetched via CMake FetchContent. Build artifacts live in a named Docker volume so the host filesystem stays clean.

Standalone Asio is used in header-only mode (ASIO_STANDALONE). No Boost dependency.