SunSpec Rust Implementation

This Rust crate contains code for accessing SunSpec compliant devices in a safe and convenient way.

Highlights

• Pure Rust library
• No unsafe code
• Panic free
• All communication is abstracted via traits making it runtime agnostic
• Supports Modbus TCP and RTU (via tokio-modbus).
• tokio-modbus is optional. Custom transports can implement the client trait directly.
• Implements "Device Information Model Discovery" as defined in the SunSpec specification.
• Compile-time model selection via Cargo features
• Fully typed models generated from the JSON files contained in the SunSpec models repository
• Fully typed enums
• Fully typed bitfields
• Fully documented. Even the generated models.
• Reading of complete models in a single request.
• Supports nested and repeating groups.
• Unknown or unsupported models are reported during discovery.

Features

If you only need a small subset of models, disable default features and opt in to the features and specific models you need:

[dependencies]
sunspec = { version = "...", default-features = false, features = ["tokio-modbus", "model1", "model103"] }

Examples

The examples directory in the code repository contains the unabridged code.

• examples/readme: minimal end-to-end example used in this README
• examples/model103: reading a common inverter model from a device
• examples/model712: reading a model with nested and repeating groups

Example code for accessing data from a three phase inverter using the model 103

use std::{error::Error, net::SocketAddr, time::Duration};

use clap::Parser;
use itertools::Itertools;
use sunspec::{
    client::{AsyncClient, Config},
    models::{model1::Model1, model103::Model103},
};
use tokio::time::sleep;
use tokio_modbus::client::tcp::connect;

#[derive(Parser)]
struct Args {
    addr: SocketAddr,
    device_id: u8,
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let args = Args::parse();

    let client = AsyncClient::new(connect(args.addr).await?, Config::default());
    let device = client.device(args.device_id).await?;

    let m1: Model1 = device.read_model().await?;

    println!("Manufacturer: {}", m1.mn);
    println!("Model: {}", m1.md);
    println!("Version: {}", m1.vr.as_deref().unwrap_or("(unspecified)"));
    println!("Serial Number: {}", m1.sn);

    println!(
        "Supported models: {}",
        device
            .models
            .supported_model_ids()
            .iter()
            .map(|id| id.to_string())
            .join(", ")
    );

    loop {
        let m103: Model103 = device.read_model().await?;
        let w = m103.w as f32 * 10f32.powf(m103.w_sf.into());
        let wh = m103.wh as f32 * 10f32.powf(m103.wh_sf.into());
        println!("{:12.3} kWh {:9.3} kW", wh / 1000.0, w / 1000.0,);
        sleep(Duration::from_secs(1)).await;
    }
}

FAQ

How does this crate differ from crates like tokio-sunspec, sunspec-models, sunspec_rs?

• This crate generates all code using Rust code via the official SunSpec models repository with a code generator that was written in Rust, too.

• All generated models are plain Rust structs. A single Modbus call can return the complete data for a model rather than having to fetch points individually.

• All public types are documented. Even the generated models.

• Full support for nested and repeating groups.

How do I reduce compile times or binary size?

• Disable default features and enable only the features you need.
• This is is useful if you interact only with a small number of models.

Do I have to use tokio-modbus?

• No. tokio-modbus is just the bundled transport adapter.
• You can provide your own transport by implementing the async client trait and constructing an AsyncClient with it.
• The separate tokio feature only controls tokio-based timeout handling.

What happens if a device exposes models this crate does not know?

• Discovery still succeeds.
• Known models are stored in device.models.
• Unknown model ids, addresses, and lengths are returned in device.unknown_models.

Can I scan for all slave IDs on a bus?

• Yes. AsyncClient::devices() probes slave ids 0..=255 and returns every device that responds with a valid SunSpec header.
• If you already know the slave id, use AsyncClient::device(slave_id) instead.

How do discovery addresses and timeouts work?

• The default discovery addresses are [40000, 0, 50000].
• That order avoids unnecessary timeouts on devices that do not behave well at address 0.
• You can override discovery addresses and read/write timeouts via Config.

How are large models handled?

• Models larger than the Modbus single-request limit are read in chunks and then decoded as one typed model value.
• Nested groups and repeating groups are handled by the generated model code.

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.