About this repository

This is minimal Modbus RTU implemetation for STM32 microcontrollers programed with LibOpenCM3.

• small and simple – less than 400 code lines of "core" library
• support RTU slave (most common case)
• write from scratch for STM32 / LibOpenCM3
• use LibOpenCM3 as HAL
• MIT licence
• all configuration (Modbus, UART, GPIO, Timer) via #define in single file modbusRTU_Config.h
• processing Modbus PDU in user application code via callback functions
• processing Modbus PDU can be done in ISR or main loop (depending on need and use in application)

Files

• modbusRTU.c – "core" library

• modbusRTU.h – API header (exported only function intended to use in user application code)

• modbusRTU_Config.h – all configuration settings

• modbusRTU_Debug.h – debug via GPIO (unused until define MODBUS_DEBUG macro)

• modbusCRC.h – Modbus CRC16 lookup tables

• main.c – sample application

Build

For build demo app use:

OPENCM3_DIR=/path/to/libopencm3  make

libopencm3 must be build first

Tested

Tested on STM32F103C8T6.

References

• Modbus – https://modbus.org/
• LibOpenCM3 – http://libopencm3.org/

Copyrights

Copyright (c) 2021, Robert Ryszard Paciorek [email protected], BSD/MIT-type license

This text/program is free document/software. Redistribution and use in source and binary forms, with or without modification, ARE PERMITTED provided save this copyright notice. This document/program is distributed WITHOUT any warranty, use at YOUR own risk.

The MIT License:

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.