How to Implement STM32 Bootloader via USB DFU for Firmware Updates

Implementing STM32 Bootloader via USB DFU for Firmware Updates in a Custom Embedded Application

In this tutorial, we will walk through the steps necessary to implement a bootloader for STM32 microcontrollers using USB Device Firmware Upgrade (DFU) protocol. This allows you to update the firmware of your embedded application over USB, providing a convenient method for firmware upgrades.

Prerequisites

• Basic knowledge of embedded systems and microcontrollers
• STM32 microcontroller board (e.g., STM32F4Discovery)
• Development environment set up (e.g., STM32CubeIDE or Keil)
• USB cable for connection
• STM32CubeProgrammer tool or DFU-util installed on your PC

Parts/Tools

• STM32 microcontroller (e.g., STM32F4 series)
• USB cable for connection
• STM32CubeIDE or any supported IDE
• STM32CubeProgrammer or DFU-util

Steps

1. Set Up Your Development Environment
   • Install STM32CubeIDE from the STMicroelectronics website.
   • Set up your project for the specific STM32 microcontroller you are using.
2. Configure the Bootloader
   • Create a new project for the bootloader.
   • Enable the USB Device under the Middleware settings.
   • Set the USB mode to DFU. This is typically done in the CubeMX configuration.
3. Implement the Bootloader Code

   In your bootloader project, implement the following code snippet:

   
   #include "usb_device.h"
   #include "usbd_dfu.h"
   // Other necessary includes
   
   void JumpToApplication(void) {
       // Define the application start address
       uint32_t appAddress = 0x08008000; // Change to your application start address
       void (*appJump)(void);
       
       // De-initialize the peripherals
       HAL_RCC_DeInit();
       HAL_PWR_DisableWakeUpPin(PWR_WAKEUP_PIN1);
       
       // Set the vector table offset
       SCB->VTOR = appAddress;
       
       // Get the application start address
       appJump = (void (*)(void))(*((uint32_t *)(appAddress + 4)));
       
       // Jump to the application
       __set_MSP(*((uint32_t *)appAddress));
       appJump();
   }
           

4. Build and Flash the Bootloader
   • Compile the bootloader project in STM32CubeIDE.
   • Connect your STM32 board to your computer via USB.
   • Use STM32CubeProgrammer to flash the bootloader onto the STM32 microcontroller.
   • Ensure the bootloader is set to execute on startup.
5. Prepare Your Application Code

   Create your main application project separately. Ensure the application code starts at the address defined in the bootloader.

   
   #include "stm32f4xx_hal.h"
   // Other necessary includes
   
   int main(void) {
       HAL_Init();
       // Application code here
       while (1) {
           // Main loop
       }
   }
           

6. Build and Flash the Application
   • Compile your application code in STM32CubeIDE.
   • Use STM32CubeProgrammer or DFU-util to flash the application to the appropriate memory address.
7. Testing the Bootloader and Application
   • Reset the STM32 board and let it boot into the bootloader.
   • Use DFU-util or STM32CubeProgrammer to upload a new firmware.
   • Verify that the new firmware runs correctly.

Troubleshooting

• Bootloader Not Starting:

  Ensure that the bootloader is correctly flashed and that the boot pins are set to enable the bootloader mode.

• USB Not Recognized:

  Check the USB cable and ensure that the correct drivers are installed on your computer.

• Firmware Update Fails:

  Verify the memory addresses and ensure that the firmware being uploaded is compatible with the bootloader.

Conclusion

Implementing a bootloader using USB DFU for STM32 microcontrollers enables seamless firmware updates for your embedded applications. By following this tutorial, you should be able to set up your development environment, create a bootloader, and manage firmware updates effectively. Always test thoroughly to ensure your bootloader and application work as intended.