Getting started

Building iecf

iecf is a Rust workspace with no dependencies beyond the standard library.

git clone https://github.com/raspihats/iecf
cd iecf
cargo build --release

The compiler is target/release/iecf.

Checking a program

iecf check reads IEC 61131-3 files — any number, a project’s POUs, types and configuration across them — and reports every diagnostic:

$ iecf check main.st
main.st:12:9: error[E0013]: Ed.3 Figure 11 defines no conversion from BYTE to BOOL

Each code has its explanation, also on the command line:

iecf explain E0013

--format json gives the diagnostics as JSON, for an editor.

Building C

iecf build writes the C for a project with one CONFIGURATION:

iecf build -o out *.st

out/ then holds <configuration>.c, <configuration>.h and iecf.h, the runtime header, and <configuration>.symbols.json, the symbol table for tools (The C output §6). The C is portable C99, no compiler extensions, no allocation. The C output says what the platform has to give it — a process image and a clock — and what it gives back.

A first program

PROGRAM main
VAR
    start AT %IX0.0 : BOOL;
    motor AT %QX0.0 : BOOL;
    run : TON;
END_VAR
run(IN := start, PT := T#2s);
motor := run.Q;
END_PROGRAM

CONFIGURATION plant
    RESOURCE cpu ON PLC
        TASK fast(INTERVAL := T#10ms, PRIORITY := 0);
        PROGRAM p WITH fast : main;
    END_RESOURCE
END_CONFIGURATION

Extensions

By default iecf checks the standard as written. A few things vendors accept that the standard does not — a global used without VAR_EXTERNAL, TIME converted to an integer — are extensions, each switched on by name:

iecf check --extension implicit-externals *.st

In a browser

crates/iecf-wasm builds the checker as a WebAssembly module of about 95 KB gzipped, and iecf.js wraps it:

import { load } from "./iecf.js";
const iecf = await load(fetch("iecf.wasm"));
iecf.check([{ name: "main.st", text }]);
// -> [{ code, severity, message, file, line, column, ... }]

The diagnostics are those iecf check --format json gives.