MC Protocol Serial C++

[](LICENSE)

MC Protocol Serial C++ Library

MC protocol serial library for MCU-oriented environments.

This repository is for cases like these:

• You want to talk to a Mitsubishi PLC over serial / RS-232C / RS-485
• You want a C++ library that does not allocate dynamically
• You want to run the same core logic on Linux, RP2040, ESP32-C3, or Arduino Mega 2560

The current codebase includes:

• A transport-agnostic library centered on MelsecSerialClient
• A simpler host-side synchronous entrypoint via PosixSyncClient
• PlatformIO example projects for RP2040, ESP32-C3, and Arduino Mega 2560
• Board-specific Arduino samples for RP2040, ESP32-C3, and Arduino Mega 2560
• GitHub Actions for host build/test/docs and PlatformIO compile checks
• Real-hardware validation records for RJ71C24-R2, LJ71C24, QJ71C24N, and FX5UC-32MT/D

PlatformIO Registry:

• https://registry.platformio.org/libraries/fa-yoshinobu/mcprotocol-serial-cpp

Start Here

Choose the first path that matches what you are trying to do.

1. Simplest host-side bring-up

Start with host_sync_quickstart.cpp if you want the smallest blocking example on Windows or POSIX.

• best first read for host-side use
• read-only bring-up
• uses the synchronous PosixSyncClient facade

2. Real MCU UART bring-up

Start with MCU Quickstart and Examples Index if you want to run on RP2040, ESP32-C3, or Arduino Mega 2560.

• board-specific UART samples
• read-only first step
• intended for actual TTL UART -> level shifter -> RS-232C wiring

3. Low-level async integration

Start with mcu_async_batch_read.cpp if you want the async state machine directly and plan to integrate your own UART layer or scheduler.

4. Confirm the real target settings

Before building against real hardware, confirm the exact serial settings for your target in HARDWARE_VALIDATION.md.

The example projects keep intentionally simple defaults. Those defaults are example defaults, not the authority for the current validated settings.

Documentation Map

For Users

• Examples Index
• Library Entrypoints
• PlatformIO
• Wiring Guide
• MCU Quickstart
• FAQ
• Hardware Validation Matrix
• Footprint Profiles
• Generated API Docs

For Maintainers

• Maintainer Docs Index
• Developer Notes
• Manual Command Coverage
• Docs And CI
• TODO / Current Follow-up
• Native Command Backlog
• Release Process
• Changelog

What Works Today

• The same transport-agnostic core is used by host-side tools and MCU firmware examples.
• 2C, 3C, and 4C command handling are in place. 2C is ASCII-only. The codebase also has initial 1C and 1E support for narrower subsets.
• 2C / 3C / 4C ASCII currently support Format1, Format2, Format3, and Format4. Format2 is the block-numbered variant and maps to ProtocolConfig::ascii_block_number or CLI --block-no.
• The implemented command families cover the practical device-memory, random, multi-block, monitor, host-buffer, module-buffer, CPU-model, remote-control, password/error, loopback, user-frame, and C24 extras paths described elsewhere in this repo.
• Real-hardware validation currently covers RJ71C24-R2, LJ71C24, QJ71C24N, and FX5UC-32MT/D.
• There are no active command-family holds on the currently validated targets.
• Qualified helper access over 0601/1601 is the supported public U... path.
• On the validated RJ71C24-R2 + R120PCPU iQ-R spot-device path, Jn\\... batch and multi-block surfaces are validated.

For the exact PASS / status matrix and the verified serial settings for each target, see HARDWARE_VALIDATION.md.

Current Limits

• This repository does not implement the full MC protocol serial command list. Use MANUAL_COMMAND_COVERAGE.md for the exact implemented vs. missing command families.
• 1C and 1E remain subset implementations. They are useful, but they do not expose the full 3C / 4C surface.
• Some command families are target-dependent and require the right --series selection.
• Native qualified access is not a supported public workflow. Keep U... access on the helper path only.
• Jn\\... random and monitor remain outside the currently validated public surface.
• FX5UC-32MT/D treats 0613/1613/0601/1601 and 0801/0802 as unsupported / not applicable on serial 3C/4C.
• Large contiguous write-words and write-bits are still split automatically to fit fixed request buffers.
• The current active follow-up is target-dependent validation for 1005 remote latch clear and 1630 / 1631 remote password unlock/lock on RJ71C24-R2 + R120PCPU. Parked implementation gaps such as 1612, 0630, and 2101 remain documented in TODO.md.

For target-specific limits and current follow-up items, use HARDWARE_VALIDATION.md and TODO.md.

Library Use

The library exposes three practical entry paths:

• high-level request builders in mcprotocol/serial/high_level.hpp
• synchronous host-side bring-up in mcprotocol/serial/host_sync.hpp
• low-level async integration through MelsecSerialClient

Use these docs for the details:

• Library Entrypoints
• MCU Quickstart
• Examples Index

PlatformIO and Build Profiles

PlatformIO packaging, environment names, reduced/ultra profiles, and build-time tuning macros are documented here:

• PlatformIO
• Footprint Profiles

Docs and CI

Local documentation tasks and GitHub automation are documented here:

• Docs And CI