TCP, USART and USB-CDC Modbus RTU Master and Slave library for STM32 microcontrollers based on Cube HAL and FreeRTOS.

Includes multiple examples for popular development boards including BluePill, NUCLEO-64, NUCLEO-144 and Discovery Boards (Cortex-M3/M4/M7).

This is a port of the Modbus library for Arduino: https://github.com/smarmengol/Modbus-Master-Slave-for-Arduino

Video demo for STM32F4-discovery board and TouchGFX: https://youtu.be/XDCQvu0LirY

NEW Script examples to test the library based on Pymodbus

NEW TCP slave (server) multi-client with configurable auto-aging algorithm for management of TCP connections

Traditional Chinese: 繁體中文

• Portable to any STM32 MCU supported by ST Cube HAL.
• Portable to other Microcontrollers, like the Raspberry PI Pico, requiring little engineering effort.
• Multithread-safe implementation based on FreeRTOS.
• Multiple instances of Modbus (Master and/or Slave) can run concurrently in the same MCU, only limited by the number of available UART/USART of the MCU.
• RS232 and RS485 compatible.
• USART DMA support for high baudrates with idle-line detection.
• USB-CDC RTU master and Slave support for F103 Bluepill board.
• TCP master and slave support with examples for F429 and H743 MCUs

├── LICENSE
├── README.md
├── Examples
    ├── ModbusBluepill --> STM32F103C8 USART Slave
    ├── ModbusBluepillUSB --> STM32F103C8 USART + USB-CDC Master and Slave 
    ├── ModbusF103 --> NUCLEO-F103RB Modbus Master and Slave
    ├── ModbusF429 --> NUCLEO-F429ZI Modbus Slave 
    ├── ModbusF429TCP --> NUCLEO-F429ZI Modbus TCP
    ├── ModbusF429DMA --> NUCLEO-F429ZI Modbus RTU DMA master and slave 
    ├── ModbusL152DMA --> NUCLEO-L152RE Modbus RTU DMA slave
    ├── ModbusH743 --> NUCLEO-H743ZI Modbus Slave
    ├── ModbusH743TCP --> NUCLEO-H743ZI Modbus TCP
    ├── ModbusF303 --> NUCLEO-F303RE Modbus Slavee
    ├── ModbusSTM32F4-discovery --> STM32F4-discovery TouchGFX + Modbus Master
├── MODBUS-LIB --> Library Folder
    ├── Inc
    │   └── Modbus.h 
    ├── Config
    │   └── ModbusConfigTemplate.h --> Configuration Template
    └── Src
        ├── Modbus.c 
        └── UARTCallback.c
 

Examples provided for STM32CubeIDE Version: 1.8.0 https://www.st.com/en/development-tools/stm32cubeide.html.

• Import the examples in the STM32Cube IDE from the system folder
• Connect your NUCLEO board
• Compile and start your debugging session!
• If you need to adjust the Baud rate or any other parameter use the Cube-MX assistant (recommended). If you change the USART port you need to enable the interrupts for the selected USART. Check UARTCallback.c for more details.

• The standard interrupt mode for Modbus RTU USART is suitable for 115200 bps or lower baud rates. For Higher baud rates---tested up to 2 Mbps---it is recommended to use the DMA mode. Check the corresponding examples. It will require extra configurations for the DMA channels in the Cube HAL.

• The USB-CDC example supports only the Bluepill development board. It has not been validated with other development boards. To use this example, you need to activate USB-CDC in your ModbusConfig.h file.

• The TCP examples have been validated with NUCLEO F429ZI and H743ZI. To use these examples, you need to activate TCP in your ModbusConfig.h file.

• The HAL implementation for LWIP TCP of the CubeMX generates code that might not work if the cable is not connected from the very beginning. This is a known issue that can be solved manually changing the generated code as detailed here: https://community.st.com/s/question/0D50X0000CDolzDSQR/ethernet-does-not-work-if-uc-starts-with-the-cable-disconnected

Check the TCP example for the NUCLEO F429, which includes the manual modifications.

• Create a new project in STM32Cube IDE for your MCU
• Enable FreeRTOS CMSIS_V2 in the middleware section of Cube-MX
• Configure a USART and activate the global interrupt
• If you are using the DMA mode for USART, configure the DMA requests for RX and TX
• Configure the Preemption priority of USART interrupt to a lower priority (5 or a higher number for a standard configuration) than your FreeRTOS scheduler. This parameter is changed in the NVIC configuration pane.
• Import the Modbus library folder (MODBUS-LIB) using drag-and-drop from your host operating system to your STM32Cube IDE project
• When asked, choose link folders and files
• Update the include paths in the project's properties to include the Inc folder of MODBUS-LIB folder
• Create a ModbusConfig.h using the ModbusConfigTemplate.h and add it to your project in your include path
• Instantiate a new global modbusHandler_t and follow the examples provided in the repository
• Note: If your project uses the USART interrupt service for other purposes you have to modify the UARTCallback.c file accordingly

Linux/Windows: https://github.com/riptideio/pymodbus

Linux: https://launchpad.net/~js-reynaud/+archive/ubuntu/qmodbus

Windows: https://sourceforge.net/projects/qmodbus/

Linux: https://sourceforge.net/projects/pymodslave/

Windows: https://sourceforge.net/projects/modrssim2/

• Implement isolated memory spaces for coils, inputs and holding registers.
• Implement wrapper functions for Master function codes. Currently, telegrams are defined manually.
• Improve function documentation
• MODBUS TCP implementation improvement to support multiple clients and TCP session management (10/24/2021)
• Improve the queue for data reception; the current method is too heavy it should be replaced with a simple buffer, a stream, or another FreeRTOS primitive. Solved Queue replaced by a Ring Buffer (03/19/2021)
• Test with Rs485 transceivers (implemented but not tested) Verified with MAX485 transceivers (01/03/2021)
• MODBUS TCP implementation (28/04/2021)