LinuxCNC HAL interface for Rust

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Documentation

A safe, high-level interface to LinuxCNC's HAL (Hardware Abstraction Layer) module.

For lower level, unsafe use, see the linuxcnc-hal-sys crate.

Development setup

bindgen must be set up correctly. Follow the requirements section of its docs.

To run and debug any HAL components, the LinuxCNC simulator can be set up. There's a guide here for Linux Mint (and other Debian derivatives).

Project setup

This crate depends on the linuxcnc-hal-sys crate which requires the LINUXCNC_SRC environment variable to be set to correctly generate the C bindings. The value must be the absolute path to the root of the LinuxCNC source code.

The version of the LinuxCNC sources must match the LinuxCNC version used in the machine control.

# Clone LinuxCNC source code into linuxcnc/
git clone https://github.com/LinuxCNC/linuxcnc.git

# Check out a specific version tag. This may also be a commit, but must match the version in use by the machine control.
cd linuxcnc && git checkout v2.8.0 && cd ..

# Create your component lib
cargo new --lib my_comp

cd my_comp

# Add LinuxCNC HAL bindings as a Cargo dependency with cargo-edit
cargo add linuxcnc-hal

LINUXCNC_SRC=/path/to/linuxcnc/source/code cargo build

If LinuxCNC is configured to run in place, liblinuxcnchal.so.0 may not be found on startup. To fix, try setting the library path with e.g. export LD_LIBRARY_PATH=~/Repositories/linuxcnc/lib

Examples

Create a component with input and output

This example creates a component called "pins" with a single input ("input-1") and output pin ("output-1"). It enters an infinite loop which updates the value of output-1 every second. LinuxCNC convention dictates that component and pin names should be dash-cased.

This example can be loaded into LinuxCNC with a .hal file that looks similar to this:

loadusr -W /path/to/your/component/target/debug/comp_bin_name
net input-1 spindle.0.speed-out pins.input-1
net output-1 pins.output-1

Pins and other resources are registered using the Resources trait. This example creates a Pins struct which holds the two pins. HalComponent::new handles component creation, resources (pin, signal, etc) initialisation and UNIX signal handler registration.

use linuxcnc_hal::{
    error::PinRegisterError,
    hal_pin::{InputPin, OutputPin},
    prelude::*,
    HalComponent, RegisterResources, Resources,
};
use std::{
    error::Error,
    thread,
    time::{Duration, Instant},
};

struct Pins {
    input_1: InputPin<f64>,
    output_1: OutputPin<f64>,
}

impl Resources for Pins {
    type RegisterError = PinRegisterError;

    fn register_resources(comp: &RegisterResources) -> Result<Self, Self::RegisterError> {
        Ok(Pins {
            input_1: comp.register_pin::<InputPin<f64>>("input-1")?,
            output_1: comp.register_pin::<OutputPin<f64>>("output-1")?,
        })
    }
}

fn main() -> Result<(), Box<dyn Error>> {
    rtapi_logger::init();

    // Create a new HAL component called `rust-comp`
    let comp: HalComponent<Pins> = HalComponent::new("rust-comp")?;

    // Get a reference to the `Pins` struct
    let pins = comp.resources();

    let start = Instant::now();

    // Main control loop
    while !comp.should_exit() {
        let time = start.elapsed().as_secs() as i32;

        // Set output pin to elapsed seconds since component started
        pins.output_1.set_value(time.into())?;

        // Print the current value of the input pin
        println!("Input: {:?}", pins.input_1.value());

        // Sleep for 1000ms. This should be a lower time if the component needs to update more
        // frequently.
        thread::sleep(Duration::from_millis(1000));
    }

    // The custom implementation of `Drop` for `HalComponent` ensures that `hal_exit()` is called
    // at this point. Registered signal handlers are also deregistered.

    Ok(())
}

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.