FreeModbus is a Modbus ASCII/RTU and Modbus TCP implementation for embedded systems. It provides an implementation of the Modbus Application Protocol v1.1a and supports the RTU/ASCII transmission modes defined in the Modbus over serial line specification 1.0. Since version 0.7 FreeModbus also supports Modbus/TCP. Version 0.9 added the first Modbus/TCP port for embedded systems using the lwIP TCP/IP stack.

This project has been ported FreeModbus RTU for ST's STM32F1 Series of mainstream MCUs

Features:

• Free
• Modbus RTU
• NO RTOS
• Keil MD5 IDE
• STM32 HAL library
• STM32CubeMX

FreeMODBUS Document: https://www.embedded-solutions.at/files/freemodbus-v1.6-apidoc/