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Changelog

All notable changes to this project are documented here.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

0.1.0

Initial release.

Core

  • Async-native serial transport built on AnyIO (>= 4.13).
  • Immutable SerialConfig with with_changes, FlowControl, RS485Config, and StrEnum types (ByteSize, Parity, StopBits).
  • Multi-inherited exception hierarchy compatible with stdlib and AnyIO bases.
  • Tri-state Capability model and SerialCapabilities snapshot per backend.
  • Backend Protocol split into SyncSerialBackend (POSIX) and AsyncSerialBackend (Windows).
  • SerialPort, SerialConnectable, and open_serial_port with full AnyIO typed-attribute support.
  • Runtime reconfiguration via port.configure(new_config) with serialized concurrent calls; failed applies leave port.config unchanged.
  • Raw-bytes API: receive, receive_available, receive_into, send, drain, drain_exact, input_waiting, output_waiting.
  • MockBackend and FaultPlan under anyserial.testing for hardware-free unit testing, plus serial_port_pair helper.
  • Blocking anyserial.sync.SerialPort wrapper backed by a process-wide BlockingPortalProvider; per-call timeout= keyword; configure_portal(backend=..., backend_options=...) for AnyIO backend selection.

Linux backend

  • LinuxBackend with nonblocking fd I/O via anyio.wait_readable / anyio.wait_writable, raw-mode termios, modem-line ioctls, BREAK, exclusive access via flock, queue-depth, and buffer flush.
  • Standard and extended baud (TCSETS2 / BOTHER).
  • ASYNC_LOW_LATENCY low-latency mode with restore-on-close.
  • Kernel RS-485 (TIOCSRS485) with read-modify-write that preserves driver-reserved bits and restores pre-touch state on close or configure(rs485=None).
  • Native sysfs-based port discovery with USB-ancestor resolution; populates VID / PID / serial / manufacturer / product / location / interface and emits a pyserial-compatible hwid string.

macOS (Darwin) backend

  • DarwinBackend with custom baud via IOSSIOSPEED, BREAK via the shared <sys/ttycom.h> numeric fallback, and UnsupportedPolicy- routed rejection of low_latency and rs485.
  • Native IOKit discovery walks IOSerialBSDClient, prefers /dev/cu.* callout paths, and climbs the IORegistry parent chain for USB metadata. The ctypes facade over IOKit + CoreFoundation loads lazily so the module imports cleanly on Linux CI.

BSD backend

  • One BsdBackend for FreeBSD / NetBSD / OpenBSD / DragonFly. Custom baud via integer c_ispeed / c_ospeed passthrough; low_latency / rs485 rejected via UnsupportedPolicy.
  • /dev-scan discovery with per-variant glob sets. USB metadata is intentionally not populated — use list_serial_ports(backend="pyserial") when VID / PID is needed.

Windows backend

  • WindowsBackend implements AsyncSerialBackend and dispatches hot-path receive / send through each runtime's native IOCP machinery:
  • Trio → trio.lowlevel.register_with_iocp + readinto_overlapped / write_overlapped.
  • asyncio on ProactorEventLoop → loop._proactor._register + _overlapped.Overlapped.ReadFileInto / WriteFile (zero-copy via CPython 3.12+ ReadFileInto).
  • No worker-thread fallback. SelectorEventLoop raises UnsupportedPlatformError at open time pointing at WindowsProactorEventLoopPolicy.
  • SetupAPI port discovery via GUID_DEVINTERFACE_COMPORT populates VID / PID / serial / manufacturer / product / location on USB-attached adapters; hwid is pyserial-compatible. Falls back to HKLM\HARDWARE\DEVICEMAP\SERIALCOMM via winreg when SetupAPI enumeration fails.
  • WaitCommEvent modem-line change notification (EV_CTS | EV_DSR | EV_RING | EV_RLSD | EV_ERR | EV_BREAK).
  • DCB round-trip (GetCommState → overlay → SetCommState) preserves vendor state stored in reserved DCB fields by FTDI / Prolific / CH340 drivers.
  • "Wait-for-any" COMMTIMEOUTS policy (MAXDWORD / MAXDWORD / 1 ms) with internal retry loop on zero-byte completions, so idle receive() doesn't surface spurious EOF.
  • Win32 error translation (ERROR_FILE_NOT_FOUND → PortNotFoundError, ERROR_ACCESS_DENIED / ERROR_SHARING_VIOLATION → PortBusyError, ERROR_INVALID_HANDLE / ERROR_OPERATION_ABORTED → SerialClosedError, ERROR_INVALID_PARAMETER on config → UnsupportedConfigurationError, ERROR_DEVICE_REMOVED / ERROR_NOT_READY / ERROR_GEN_FAILURE → SerialDisconnectedError). Exceptions carry a .winerror attribute.
  • Capability snapshot reports SUPPORTED for every feature except low_latency (no Windows equivalent of ASYNC_LOW_LATENCY) and rs485 (FTDI VCP RS-485 is driver config, not a runtime API).

Discovery

  • list_serial_ports(), find_serial_port(...), and the PortInfo data model — async, always-live, no caching.
  • Optional pyudev (Linux) and pyserial (cross-platform) backends selectable via the backend= keyword. Each raises ImportError with the exact install command when the extra isn't installed.
  • port.port_info typed attribute on SerialPort: open_serial_port resolves the device path through native discovery and exposes the result on port.port_info and via the typed-attribute interface.

Tooling and CI

  • pyproject.toml with hatchling + hatch-vcs build, AnyIO >= 4.13 runtime dep, Python 3.13 / 3.14 support.
  • uv-managed dependency groups (lint, type, test, docs, bench).
  • Ruff, mypy, pyright, pytest, coverage, pre-commit configuration.
  • GitHub Actions CI for lint, typecheck, and tests on Linux, macOS, and Windows across Python 3.13 / 3.14 × asyncio / asyncio + uvloop / trio (Windows: asyncio Proactor / trio). FreeBSD smoke job via cross-platform-actions.
  • Hardware test marker default-deselected (pytest -m "not hardware"); opt-in via pytest -m hardware with ANYSERIAL_TEST_PORT.
  • Benchmark suite under benchmarks/: receive / send latency, throughput, many-port fan-out, allocation profile, sync-vs-async, Windows IOCP scenarios over an opt-in configured serial pair, and a pyserial-asyncio head-to-head. Nightly bench workflow records baselines per backend.

Documentation

  • Full documentation site covering quickstart, configuration, capabilities, discovery, runtime reconfiguration, RS-485, AnyIO backend selection, uvloop, cancellation, performance, sync wrapper, hardware testing, troubleshooting, migration from pySerial, and per-platform pages (Linux tuning, macOS, BSD, Windows).
  • MIT license.