Detailed Process of Porting Modbus on STM32 Bare Metal

1. Preparation

• Hardware: STM32 development board, Modbus adapter (such as RS485 converter), Dupont wires, etc.

• Software: STM32CubeIDE or Keil MDK-ARM, Modbus library (such as libmodbus).

2. Configure STM32

• Use STM32CubeMX or Keil’s configuration tool to configure the appropriate clock, GPIO, etc. for your STM32.

• Make sure you have enabled UART communication.

3. Install Modbus Library

• Download and install the libmodbus library. This is a popular open-source Modbus library that can be used for C and C++.

• Copy the libmodbus library files into your STM32 project directory.

4. Configure Modbus Library

• In your code, configure libmodbus to use the correct serial port and baud rate.

• You may need to modify the source code of libmodbus to fit your hardware and requirements.

5. Implement Modbus Functionality

• Implement Modbus functionality according to your needs, such as reading and writing coils, holding registers, etc.

• Use the functions provided by the libmodbus library to communicate with Modbus devices.

6. Testing and Debugging

• Run your program on the development board and use serial tools (such as PuTTY) or other Modbus tools for testing and debugging.

• Check if the data is transmitted correctly and handle any communication errors.

7. Optimization and Improvement

• Optimize the code as needed to improve communication efficiency.

• Adjust Modbus functionality according to actual application requirements.

Notes

• Modbus protocol has various variants (such as Modbus TCP, Modbus RTU, Modbus ASCII), and you need to choose the appropriate implementation based on your needs.

• Ensure that you follow the relevant Modbus specifications and standards.

• When communicating, pay attention to data verification, error handling, and retry mechanisms.

This tutorial is a high-level overview, and the specific implementation details will vary depending on your hardware and requirements. You may need to refer to more detailed documents and tutorials to gain a deeper understanding of each step.

From an application perspective, to use Modbus, the interfaces that need to be called are actually just a few. Here, I will share some commonly used source code modules during the porting process.

/* Include necessary header files */  #include <modbus.h>  #include "stm32xxxx.h" // Replace according to your STM32 model    /* Module 1: Serial Communication Module */  // Used to initialize the serial port and configure serial communication parameters  void serial_init(void) {      // Use STM32's standard library functions to initialize USART, adjustments are needed based on your specific hardware configuration  }    /* Module 2: Modbus Configuration Module */  // Used to configure the libmodbus library and set Modbus parameters  void modbus_config(void) {      modbus_t *ctx; // Context pointer for the libmodbus library      uint8_t *tab_slave_ids; // Pointer to the slave ID array      int nb_slaves; // Number of available slaves        // Create Modbus RTU communication context      ctx = modbus_new_rtu("/dev/ttyUSB0", SERIAL_PORT_SPEED, 'N', 8, 1);      if (ctx == NULL) {          fprintf(stderr, "Unable to create the libmodbus context\n");          return;      }        // Set slave ID      modbus_set_slave(ctx, MODBUS_SLAVE_ID);        // Get the number of available slaves      nb_slaves = modbus_get_slave_nb(ctx);      if (nb_slaves <= 0) {          fprintf(stderr, "No slaves available\n");          return;      }        // Get the slave ID array      tab_slave_ids = modbus_get_slave_ids(ctx);      if (tab_slave_ids == NULL) {          fprintf(stderr, "Unable to get slaves ids\n");          return;      }          // More configurations can be added here, such as handling read/write requests, error handling, etc.  }    /* Module 3: Modbus Data Processing Module */  // Core logic for processing Modbus requests and responses, can be further expanded and customized based on needs  void modbus_data_handler(modbus_t *ctx) {      // Add code logic to handle Modbus requests and responses here  }    /* Main function */  int main(void) {      /* Initialize serial communication */      serial_init(); // Initialize serial communication          /* Configure libmodbus library */      modbus_config(); // Configure libmodbus library and set Modbus parameters          /* Main loop, process Modbus requests and responses */      while (1) {          modbus_data_handler(ctx); // Core logic for handling Modbus data requests and responses          // More logic can be added here, such as error handling, sending heartbeat packets, etc.      }          return 0;  }

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