canopen-rs

A no_std-first CANopen (CiA 301) protocol stack in Rust, built to run unchanged on a bare-metal microcontroller node and on a host (Linux/SocketCAN).

Status: early development (0.1). The API will change before 1.0, but the object dictionary, SDO client/server, PDO, NMT, SYNC, EMCY, and EDS parsing are implemented and tested.

Why

The Rust CANopen landscape has several partial attempts but no clear winner — and none delivers a stack that works on both embedded and host targets. That dual target is exactly what people keep asking for. canopen-rs closes that gap with a transport-agnostic, allocation-free core and a thin host layer on top.

What works today

Everything in the core is #![no_std], #![deny(unsafe_code)], and builds for thumbv7em-none-eabihf; SDO frame codecs are validated against known-good byte sequences, and the client/server are exercised end-to-end.

Install

[dependencies]
canopen-rs = "0.1"      # no_std core: OD, SDO, PDO, NMT, SYNC, EMCY
canopen-host = "0.1"    # std host layer: SocketCAN transport + EDS parsing

The core is no_std by default; enable std for std::error::Error impls (canopen-rs = { version = "0.1", features = ["std"] }). On a microcontroller, depend only on canopen-rs and drive it with your HAL's embedded-can implementation — no host crate needed. In canopen-host, the SocketCAN transport is compiled only on Linux; EDS parsing builds everywhere. MSRV: Rust 1.75.

Quickstart

Serve an object dictionary (a device node)

use canopen_rs::{Address, Entry, NodeId, ObjectDictionary, Value};
use canopen_rs::node::Node;

// Build the node's object dictionary and wrap it in a Node.
let mut od = ObjectDictionary::<16>::new();
od.insert(Address::new(0x1000, 0), Entry::constant(Value::Unsigned32(0x0004_0192)))?;
od.insert(Address::new(0x1017, 0), Entry::rw(Value::Unsigned16(1000)))?;
let mut node = Node::new(NodeId::new(0x10)?, od);

let boot = node.boot();                 // enter pre-operational, announce boot-up
// send `boot` on the bus, then in your receive loop:
if let Some(tx) = node.on_frame(cob_id, &data) {
    // send `tx.data()` on `tx.cob_id`
}

Node bundles the object dictionary, SDO server, and NMT state: on_frame serves SDO requests (expedited or segmented, with standard abort codes), advances NMT from node-control commands, and applies received PDOs. Add PDOs with node.add_rpdo/add_tpdo, and get SYNC-triggered transmit frames from node.sync_tpdos(). It's sans-I/O — the same code runs on a host or an MCU.

Talk to a device (a master), over SocketCAN

use std::time::Duration;
use canopen_host::transport::SocketCan;
use canopen_rs::{Address, DataType, NodeId, Value};

let bus = SocketCan::open("can0")?;                 // or "vcan0" for a virtual bus
bus.set_read_timeout(Duration::from_millis(500))?;
let node = NodeId::new(0x10)?;

// Read object 0x1000 (device type). Expedited or segmented is handled for you.
let device_type = bus.sdo_read(node, Address::new(0x1000, 0), DataType::Unsigned32)?;

// Write object 0x1017 (producer heartbeat time).
bus.sdo_write(node, Address::new(0x1017, 0), Value::Unsigned16(1000))?;

On a microcontroller, use the canopen_rs::transport::{frame_from, cob_id} helpers with any HAL that implements the embedded-can traits instead of SocketCAN — the client and server code is identical.

Load a device's EDS file into an object dictionary

use canopen_host::eds::Eds;

let eds = Eds::from_file("device.eds")?;
println!("{:?}: {} objects", eds.vendor_name, eds.objects.len());
let od = eds.object_dictionary::<256>()?;   // the same OD type a node runs

Testing & validation

cargo test --workspace                                     # unit + integration + doc tests
cargo build -p canopen-rs --target thumbv7em-none-eabihf   # confirm the core stays no_std
cargo clippy --workspace --all-targets

• Independent wire-format cross-check. The frame codecs are validated against [python-canopen], a mature implementation used against real hardware — every SDO / NMT / EMCY / SYNC / PDO frame matches byte-for-byte (21/21). It runs offline:

  python3 -m pip install canopen
  python3 tools/interop/python_canopen_oracle.py
  

• On-bus loopback (Linux, no hardware). Walk the whole stack over a virtual CAN interface — LSS node-id assignment, SDO (expedited + segmented), NMT, a SYNC-triggered PDO exchange, and a block transfer — exercising the SocketCAN transport on a real bus:

  sudo tools/vcan_setup.sh                               # bring up vcan0
  cargo run -p canopen-host --example vcan_loopback
  

Design

• core (canopen-rs) — no_std, allocation-free, transport-agnostic. The object dictionary, the message codecs, the NMT state machine, and the SDO server/client. The server and client are sans-I/O: they consume and produce frames but never touch a bus, so the same logic runs on host and MCU. CAN frames flow through the embedded-can traits.
• host (canopen-host) — std layer on the core: a Linux SocketCAN transport with one-call sdo_read / sdo_write, and EDS/DCF parsing. SocketCAN is gated to Linux; EDS parsing builds everywhere.

canopen-rs/
├── core/   # no_std core protocol stack  (crate: canopen-rs)
└── host/   # std host transport + EDS     (crate: canopen-host)

References studied (not copied)

• The Python canopen library — the most complete reference for the object model, SDO/PDO semantics, and EDS handling (host-only, BSD-licensed).
• zencan — the most advanced Rust prior art.
• The CiA 301 specification as the authoritative source of truth.

License

Licensed under either of MIT or Apache-2.0 at your option. Unless you explicitly state otherwise, any contribution you submit for inclusion shall be dual-licensed as above, without additional terms.