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Frost

Frost is an open-source framework for developing, testing and deploying the software that controls and supervises industrial machines. It lets you build that software against a virtual plant — a digital twin — and validate it before running it on real equipment.

Frost is a library of Lingua Franca reactors. Lingua Franca is a coordination language whose programs execute deterministically over a logical clock, which is what makes a Frost scenario reproducible.

glacier-project/frost

This documentation follows the dev branch

dev is Frost's default branch and its current line of development. The released version, v1.0.0, has different component names. See Versions before copying code into a project that pins a release.

The shape of a Frost program

A Frost program is a Lingua Franca main reactor that instantiates components and wires their channels together. Everything you write extends FrostReactor.

Main.lf
target Python {
    fast: true,
    timeout: 1 h
}

import FrostLink from "../../src/lib/FrostLink.lf"
import FrostReactor from "../../src/lib/FrostReactor.lf"

preamble {=
    from frost import *
=}

reactor Machine extends FrostReactor {
    reaction (startup) {=
        # Bind a Python function to a method declared in the data model.
        self.data_model.get_node("Machine/Square").callback = lambda n: n * n
    =}
}

main reactor {
    machine = new Machine(name="machine")
    link = new FrostLink(name="frost_link", width=1)

    machine.channel_out -> link.channel_in
    link.channel_out -> machine.channel_in after 0
}

Three things are worth noticing.

A component's name is its address. name="machine" is both the reactor's identifier and the target other components put in the messages they send it.

The data model is not passed here. Each component's data model file is named in the configuration file, keyed by the component's name. This keeps a .lf file free of paths.

FrostLink has a width. It is a multiport router: width must match the number of components wired to it.

Where to go

  • Components

    The six reactors Frost provides, what each one contributes, and how they inherit from each other.

    Components

  • Data model

    Declaring a machine's variables and methods in YAML, and connecting them to OPC UA or MQTT.

    Data model

  • Examples

    Worked programs: registering with a link, invoking a method, subscribing to a variable.

    Examples

  • Configuration

    The YAML file that supplies data model paths, logging levels and per-component parameters.

    Configuration

Requirements

Frost needs the Lingua Franca compiler, a JDK for it to run on, and Python.

Requirement Version
Lingua Franca (lfc) installed via curl -Ls https://install.lf-lang.org \| bash -s cli
Java 17 (the version Frost's CI uses)
Python 3.12 or later (Frost's CI tests 3.12 and 3.13)
make for the test targets

Python dependencies are installed with pip install -r requirements.txt from the repository root. That pulls in machine-data-model, frost-planner and fmpy.

Licence

Frost is released under the BSD 2-Clause licence.