sequencer-rs

Rust-native EPICS sequencer — SNL compiler and runtime for state machine execution with Channel Access I/O.

No C dependencies. Just cargo build.

Workspace

Features

Runtime (seq)

• State set execution with async pvGet/pvPut/pvMonitor
• Channel management with CA lifecycle (connect/disconnect)
• Event flag coordination across state sets
• Completion types: Default, Sync, Async
• Program builder API for constructing sequencer programs
• ProgramVars / ProgramMeta traits for generated code interface

Compiler (snc-core)

• Full SNL syntax lexer and parser
• Abstract Syntax Tree (AST) generation
• Intermediate Representation (IR) lowering
• Semantic analysis and validation
• Rust code generation from IR

Architecture

sequencer-rs/
  seq/
    src/
      lib.rs             # Public API
      channel.rs         # Active CA channel management
      channel_store.rs   # Central channel value storage
      state_set.rs       # State set execution (pvGet/pvPut/pvMonitor)
      event_flag.rs      # Event flag management with wakeup
      program.rs         # ProgramBuilder and ProgramShared
      variables.rs       # ProgramVars, ProgramMeta traits
      macros.rs          # Utility macros
      error.rs           # Error types
  snc-core/
    src/
      lib.rs             # Public API
      lexer.rs           # SNL tokenization
      parser.rs          # Token → AST parsing
      ast.rs             # Abstract syntax tree
      ir.rs              # Intermediate representation
      codegen.rs         # IR → Rust code generation
      analysis.rs        # Semantic analysis
      preprocess.rs      # Preprocessing
      error.rs           # Compiler errors
  snc/
    src/main.rs          # CLI compiler
  examples/
    demo/                # Example sequencer program
  opi/
    medm/                # MEDM .adl screens (from C++ sequencer)
    pydm/                # PyDM .ui screens (converted via adl2pydm)

Quick Start

Compile SNL to Rust

snc my_program.st -o my_program.rs

Runtime Usage

use seq::{ProgramBuilder, StateSetContext};

let program = ProgramBuilder::new("my_seq")
    .channel("temperature", "TEMP:VALUE")
    .event_flag("tempChanged")
    .state_set("monitor", |ctx| async move {
        // State machine logic
    })
    .build();

program.run().await?;

Testing

cargo test --workspace

75 tests covering runtime (channel store, event flags, state sets) and compiler (lexer, parser, analysis, codegen, preprocessing).

Dependencies

• epics-base-rs — CA client library
• tokio — async runtime
• clap — CLI argument parsing (snc)

Requirements

• Rust 1.70+
• tokio runtime

License

MIT