mbus-serial

mbus-serial is a helper crate for modbus-rs.

It provides serial transport implementations for Modbus RTU and Modbus ASCII, built on top of the shared transport abstractions in mbus-core.

Native std sync transport (Transport) via serialport
Native std async transport (AsyncTransport) via tokio-serial (feature-gated)
Browser Web Serial transport for wasm32 (feature-gated)

If you want an all-in-one entry point, use modbus-rs. If you need direct access to serial transport internals, use mbus-serial directly.

Helper Crate Role

mbus-serial is intentionally focused on transport concerns:

Implements Transport from mbus-core.
Connects to real serial ports via the serialport crate.
Supports both RTU (StdRtuTransport) and ASCII (StdAsciiTransport) modes.
Provides async tokio serial transports (TokioRtuTransport, TokioAsciiTransport) behind the async feature.
Provides wasm Web Serial transports (WasmRtuTransport, WasmAsciiTransport) for wasm32 targets behind the wasm feature.

This crate does not implement high-level request/response orchestration by itself. That logic lives in mbus-client.

What Is Included

StdSerialTransport, StdRtuTransport, StdAsciiTransport (native sync Transport impls)
TokioRtuTransport, TokioAsciiTransport (native async AsyncTransport impls, async feature)
WasmRtuTransport, WasmAsciiTransport (browser wasm transports, wasm feature + wasm32 target)
Serial connection handling (open/close/check connection)
ADU send/receive support
Error mapping from I/O errors to TransportError / MbusError
Utility function to enumerate serial ports on native targets (available_ports)

Public API Surface

The crate re-exports, depending on target/features:

Native (non-wasm): StdSerialTransport, StdRtuTransport, StdAsciiTransport
Native + async: TokioRtuTransport, TokioAsciiTransport
wasm32 + wasm: WasmRtuTransport, WasmAsciiTransport

Usage

1) Add dependencies

[dependencies]
modbus-rs = "0.14.0"

2) Create serial config and transport

use modbus_rs::{
	BackoffStrategy, BaudRate, DataBits, JitterStrategy, MbusError, ModbusConfig,
	ModbusSerialConfig, Parity, SerialMode,
	StdRtuTransport, Transport,
};

fn connect_serial() -> Result<(), MbusError> {
	let config = ModbusConfig::Serial(ModbusSerialConfig {
		port_path: "/dev/ttyUSB0".try_into().map_err(|_| MbusError::BufferTooSmall)?,
		mode: SerialMode::Rtu,
		baud_rate: BaudRate::Baud19200,
		data_bits: DataBits::Eight,
		stop_bits: 1,
		parity: Parity::Even,
		response_timeout_ms: 1000,
		retry_attempts: 3,
		retry_backoff_strategy: BackoffStrategy::Immediate,
		retry_jitter_strategy: JitterStrategy::None,
		retry_random_fn: None,
	});

	let mut transport = StdRtuTransport::new();
	transport.connect(&config)?;

	// send/recv calls are used by higher-level client code

	transport.disconnect()?;
	Ok(())
}

3) List available serial ports

use modbus_rs::StdRtuTransport;

fn list_ports() {
	match StdRtuTransport::available_ports() {
		Ok(ports) => {
			for p in ports {
				println!("{}", p.port_name);
			}
		}
		Err(e) => eprintln!("failed to list ports: {}", e),
	}
}

Feature Flags

logging: enables log facade diagnostics in serial transports
async: enables tokio-backed async serial transports (TokioRtuTransport, TokioAsciiTransport)
wasm: enables Web Serial support for wasm32 targets (WasmRtuTransport, WasmAsciiTransport)

Configuration Notes

Use StdRtuTransport::new() with SerialMode::Rtu configs and StdAsciiTransport::new() with SerialMode::Ascii configs. If they do not match, connect returns TransportError::InvalidConfiguration.
stop_bits must be 1 or 2.
response_timeout_ms controls serial read timeout behavior.
Async transport uses Tokio*Transport::new(&config) and validates mode similarly via MbusError::InvalidConfiguration.

Logging

mbus-serial supports optional logging via the log facade.

Enable feature: logging
This only emits through the facade; your application provides a logger backend.

Example dependency setup:

[dependencies]
mbus-serial = { version = "0.14.0", features = ["logging"] }
env_logger = "0.11"

Platform Notes

Uses the serialport crate under the hood.
Error behavior can vary by driver/OS.
Some pseudo-terminals (especially on macOS) may not support all serial parameter operations.

Typical Integration Pattern

In most applications, mbus-serial is used together with mbus-client:

Build ModbusConfig::Serial(...).
Instantiate StdRtuTransport or StdAsciiTransport.
Pass transport into ClientServices from mbus-client.
Use client services for function-code operations.

License

This project is licensed under GNU GPL v3.0. See LICENSE for details.

This crate is licensed under GPLv3. Commercial licenses are also available for proprietary use; contact ch.raghava44@gmail.com.

Contact

For questions or support:

Name: Raghava Ch
Email: ch.raghava44@gmail.com

mbus-serial 0.14.0