How to Implement a UART Bootloader for STM32 with DFU Firmware Update

Implementing a UART-based Bootloader for STM32 with Firmware Update using DFU over USB

This tutorial will guide you through the process of implementing a UART-based bootloader for STM32 microcontrollers, enabling firmware updates via Device Firmware Upgrade (DFU) over USB. We will cover prerequisites, necessary parts, detailed steps, troubleshooting tips, and a conclusion.

Prerequisites

• Basic knowledge of embedded systems and STM32 microcontrollers.
• STM32 development board (e.g., STM32F4 Discovery).
• STM32CubeIDE or any compatible IDE installed.
• USB to UART converter (if not using an onboard UART).
• Firmware source code for the application to be loaded.
• DFU drivers installed on your PC.

Parts/Tools

• STM32 Microcontroller
• USB to UART Converter
• STM32CubeIDE
• DFU Flashing Tool (e.g., STM32CubeProgrammer)

Steps

1. Set Up Your Development Environment
   • Install STM32CubeIDE from the STMicroelectronics website.
   • Install STM32CubeMX for easier configuration of peripherals.
2. Create a New Project
   • Open STM32CubeIDE and create a new STM32 project.
   • Select your STM32 microcontroller model.
3. Configure UART Peripheral
   • In the configuration tool, enable the UART peripheral.
   • Set the baud rate (e.g., 115200 bps) and other parameters.
4. Implement Bootloader Code

   
   // Bootloader main function
   void Bootloader_Main(void) {
       // Initialize UART
       UART_Init();
   
       // Wait for DFU command
       if (Receive_DFU_Command()) {
           // Handle DFU Update
           DFU_Update();
       } else {
           // Jump to Application
           Jump_To_Application();
       }
   }
           

5. Implement DFU Update Functionality

   
   void DFU_Update(void) {
       // Receive firmware data over UART
       while (Receive_Data(&firmware_data)) {
           // Write data to Flash
           Flash_Write(&firmware_data);
       }
       // Verify and Set application as valid
   }
           

6. Compile and Flash Bootloader
   • Compile the project in STM32CubeIDE.
   • Flash the bootloader to your STM32 using the built-in programmer or an ST-Link.
7. Testing the Bootloader
   • Connect the USB to UART converter to your STM32 and PC.
   • Open a terminal program (e.g., PuTTY) to monitor UART output.
   • Send a DFU command from the terminal to initiate the firmware update process.
8. Deploy New Firmware

   
   // Example command to send firmware data
   sendFirmwareData(firmware_file);
           

Troubleshooting

• Bootloader Not Responding: Ensure that UART settings (baud rate, parity) match between the STM32 and your terminal program.
• Data Corruption: Check the integrity of the firmware file being sent.
• DFU Not Recognized: Make sure the DFU drivers are properly installed on your PC.
• Flashing Issues: Verify that the Flash memory address being written to is correct and not in use by the bootloader.

Conclusion

In this tutorial, you successfully implemented a UART-based bootloader for an STM32 microcontroller, allowing for firmware updates via DFU over USB. By following these steps, you can enhance your embedded applications with the ability to update firmware safely and efficiently. Ensure to test thoroughly in your application environment to catch any potential issues.