anymodbus¶

Async-native Modbus RTU client for Python, built on AnyIO and anyserial.

Alpha

The v0.1 surface is implemented and tested but has not yet been exercised against a wide range of real hardware. Expect minor API tweaks before v1.0. See DESIGN.md for the full plan.

What it is¶

A small, opinionated Modbus RTU client built on AnyIO and anyserial. The design tradeoffs that distinguish it from pymodbus (the dominant existing library):

AnyIO-native — works under asyncio, uvloop, and trio.
Tx-side enforced 3.5-character inter-frame gap before each send.
Idempotent-only retries by default — writes do not silently retry.
Strict typing — mypy strict plus pyright strict.
Required baudrate and parity — no spec-vs-real-device default trap.
Narrow scope — RTU client only.

For TCP, ASCII, server-side support, or a battle-tested option, use pymodbus. See Migration from pymodbus for an honest comparison.

What it isn't¶

A Modbus server.
A Modbus ASCII implementation.
A Modbus TCP implementation (planned for v0.3).
A device driver. Vendor-specific register maps and quirks belong in downstream packages layered on top.

Where to start¶

Quickstart — minimal async + sync examples.
RTU framing — the wire format and why we read by length.
Decoders — the float/int32 word-order matrix.
Migration from pymodbus — what anymodbus does differently and why.
Design — full architecture document.

License¶

MIT.