How to Implement STM32 UART Bootloader for Firmware Updates on Nucleo Boards

Introduction

The STM32 UART bootloader allows you to update firmware on STM32 Nucleo boards via serial communication. This tutorial will guide you through implementing the bootloader for firmware updates using the UART interface. By the end, you will have a working bootloader that can receive firmware updates over a serial connection.

Prerequisites

• Basic knowledge of embedded systems and microcontrollers.
• STM32 Nucleo board.
• STM32CubeIDE or any other suitable development environment.
• USB to UART converter (if your Nucleo board does not support USB direct connection).
• Firmware project ready for upload.

Parts/Tools

• STM32 Nucleo board (e.g., Nucleo-F401RE)
• USB to UART converter (if necessary)
• STM32CubeIDE or STM32CubeMX
• Terminal software (e.g., PuTTY, Tera Term)

Steps

1. Set Up Your Development Environment
   1. Install STM32CubeIDE or STM32CubeMX.
   2. Create a new project for your Nucleo board.
2. Configure UART for Bootloader
   1. Open the .ioc file in STM32CubeIDE.
   2. Enable the UART peripheral:
      • Set the mode to Asynchronous.
      • Configure the baud rate (e.g., 115200).
   3. Generate the project files by clicking “Project” > “Generate Code”.
3. Implement the Bootloader Code
   1. Create a new C file named bootloader.c in your project.
   2. Write the UART initialization code:

      
      void UART_Init(void) {
          // UART initialization code here
          HAL_UART_Init(&huart2);
      }
      

   3. Implement a function to receive firmware data:

      
      void ReceiveFirmware(uint8_t* buffer, uint16_t length) {
          HAL_UART_Receive(&huart2, buffer, length, HAL_MAX_DELAY);
      }
      

   4. Add a function to write the received data to flash memory (ensure to unlock flash before writing):

      
      void WriteToFlash(uint32_t address, uint8_t* data, uint32_t length) {
          HAL_FLASH_Unlock();
          // Flash writing code here
          HAL_FLASH_Lock();
      }
      

4. Integrate the Bootloader into the Main Application
   1. Modify the main function to call the bootloader:

      
      int main(void) {
          HAL_Init();
          SystemClock_Config();
          UART_Init();
          
          // Start receiving firmware
          uint8_t firmwareBuffer[SIZE]; // Define SIZE appropriately
          ReceiveFirmware(firmwareBuffer, SIZE);
          WriteToFlash(FLASH_ADDRESS, firmwareBuffer, SIZE);
          
          // Jump to application
          JumpToApplication();
      }
      

   2. Ensure to handle the jump to the main application properly.
5. Testing the Bootloader
   1. Compile and upload the bootloader code to your Nucleo board.
   2. Use terminal software to send firmware data to the board.
   3. Check for successful reception and writing of firmware.

Troubleshooting

• UART Communication Issues: Ensure the baud rate matches between the Nucleo board and terminal software.
• Firmware Not Writing: Check if the flash memory is unlocked before writing. Ensure the address is correct.
• Stuck in Bootloader: Confirm the jump to the main application is implemented correctly.

Conclusion

Implementing an STM32 UART bootloader for firmware updates via serial communication on Nucleo boards is a straightforward process. Following the steps outlined in this tutorial, you should now have a functioning bootloader ready to receive and write firmware updates. This setup enables easy firmware management and enhances the flexibility of your embedded applications.