# cwalter-at/freemodbus

BSD licensed MODBUS RTU/ASCII and TCP slave

Repository: https://github.com/cwalter-at/freemodbus
Canonical: https://ross.abutalabs.com/products/freemodbus
Language: C
License Family: other
Last push: 2026-06-24T08:31:53+00:00

## Health v2 (maintenance only)
Score: 63/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 89, release rhythm 8, longevity 100
- inputs: {"age_days": 2888, "days_push": 70, "days_rel": 460, "gap_med": null, "n_releases_24m": 1}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1088, forks 483 (observed 2026-08-28T04:03:32.595070+00:00)

## What it is
FreeModbus is a BSD-licensed Modbus ASCII/RTU and Modbus TCP slave (server) implementation for embedded systems, implementing the Modbus Application Protocol v1.1a. It is written in C with portable core protocol code and hardware-specific port layers for various microcontroller demos.

## Use cases
- implement a Modbus slave on an embedded microcontroller
- expose sensor data over Modbus RTU or ASCII serial lines
- serve Modbus TCP requests from an embedded device
- integrate an embedded device with SCADA or PLC systems
- port a Modbus protocol stack to a custom hardware platform

## When to choose
- you need a lightweight, BSD-licensed Modbus slave stack for an embedded C project
- you need both serial (RTU/ASCII) and TCP Modbus support
- you want a mature, widely used protocol implementation you can port to your own hardware

## When to avoid
- you need a Modbus master/client implementation rather than a slave
- you need an actively maintained project with official vendor support
- you want a high-level library for desktop or server-side Modbus communication

## Facets
- artifact type: library
- maturity: maintenance
- function: embedded, networking, serialization
- domain: embedded-systems
- platform: embedded, c, cross-platform
- tags: modbus, modbus-tcp, modbus-rtu, modbus-ascii, slave, industrial-automation, protocol-stack, bsd-license, automation, industrial, protocols

## Member repositories
- cwalter-at/freemodbus (main) score 63

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:32.595070+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T06:49:21.402896+00:00, confidence not recorded.
  - readme: https://github.com/cwalter-at/freemodbus (fetched 2026-08-28T04:03:32.595070+00:00, sha a7c904cf12ef)
- Data as of 2026-08-30T08:39:29.467469+00:00.