I have written a custom bootloader that is running on a Nucleo-L433RC-P board.
The application uses USB CDC to call the bootloader and the bootloader uses USB DFU to download the application.
I wanted to use USB to call the custom bootloader, rather than having to use a physical switch on the BOOT0 pin to call the internal bootloader
I can successfully download a simple application which just flashes an LED using the USB DFU bootloader.
However, when I download my actual project, it appears to download successfully but does not run.
My actual project is more complicated and uses the following peripherals:
- RTC
- SPI2 and DAC1 (using DMA)
- SPI1
- TIM6
- TIM7
- I2C1
- I2C2
- USB
- Shutdown and standby using WKUP and RTC wake sources
I used the following guide to write the custom bootloader and simple application...
The following web tool is used to download the application...
I have spent days trying to debug why my actual project will not work, yet the simple application does.
Now I am at a complete loss and don't know how to proceed.
The implementation is shown below.
Bootloader USB configuration...
Changes to bootloader linker script...
Bootloader main.c...
#include "main.h"
#include "usb_device.h"
typedef void (*pFunction)(void);
#define DFU_BOOT_FLAG 0xDEADBEEF
RTC_HandleTypeDef hrtc;
uint32_t dfu_boot_flag;
pFunction JumpToApplication;
uint32_t JumpAddress;
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_RTC_Init(void);
int main(void)
{
HAL_Init();
SystemClock_Config();
MX_GPIO_Init();
MX_USB_DEVICE_Init();
MX_RTC_Init();
dfu_boot_flag = HAL_RTCEx_BKUPRead(&hrtc, RTC_BKP_DR5);
if (dfu_boot_flag != DFU_BOOT_FLAG)
{
if (((*(__IO uint32_t*) USBD_DFU_APP_DEFAULT_ADD) & 0x2FFC0000) == 0x20000000)
{
JumpAddress = *(__IO uint32_t*) (USBD_DFU_APP_DEFAULT_ADD + 4);
JumpToApplication = (pFunction) JumpAddress;
__set_MSP(*(__IO uint32_t*) USBD_DFU_APP_DEFAULT_ADD);
JumpToApplication();
}
}
HAL_RTCEx_BKUPWrite(&hrtc, RTC_BKP_DR5, 0); // So next boot won't be affected
uint32_t now = 0, next_blink = 100;
while (1)
{
now = uwTick;
if (now >= next_blink)
{
HAL_GPIO_TogglePin(STATUS_LED_GPIO_Port, STATUS_LED_Pin);
next_blink = now + 100;
}
}
}
Changes to bootloader usbd_dfu_if.c....
Changes to bootloader usbd_dfu_if.h....
Changes to application linker script...
Simple application main.c...
#include "main.h"
#include "usb_device.h"
#define DFU_BOOT_FLAG 0xDEADBEEF
#define DFU_BOOT_REQ 0xAA
RTC_HandleTypeDef hrtc; uint32_t *dfu_boot_flag;
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_RTC_Init(void);
int main(void)
{
uint32_t now = 0, next_blink = 1000;
HAL_Init();
SystemClock_Config();
MX_GPIO_Init();
MX_USB_DEVICE_Init();
MX_RTC_Init();
HAL_PWR_EnableBkUpAccess();
while (1)
{
now = uwTick;
if (now >= next_blink)
{
HAL_GPIO_TogglePin(STATUS_LED_GPIO_Port, STATUS_LED_Pin);
next_blink = now + 1000;
}
}
}
#define USB_RX_BUF_SIZE 512
volatile uint8_t usb_rx_buffer[USB_RX_BUF_SIZE];
volatile uint32_t usb_rx_count = 0; // number of bytes in buffer
void USB_CDC_RxHandler(uint8_t* Buf, uint32_t Len)
{
if ((usb_rx_count + Len) < USB_RX_BUF_SIZE)
{
memcpy((uint8_t *)&usb_rx_buffer[usb_rx_count], Buf, Len);
usb_rx_count += Len;
}
if (usb_rx_buffer[0] == DFU_BOOT_REQ)
{
HAL_RTCEx_BKUPWrite(&hrtc, RTC_BKP_DR5, DFU_BOOT_FLAG);
HAL_NVIC_SystemReset();
}
}
Changes to application system_stm32l4xx.c...
Changes to application usbd_cdc_if.c...
Thanks TDK, these things are never straight forward are they !
I used the example from the link you sent, the only modification I made was to enable the USB CDC so that I can call JumpToBootloader when 0xAA is received via USB.
However, when the bootloader is called the computer does not see the USB DFU device.
If I pause the debugger, it shows the following...
My code is below...
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2025 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
*/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "usb_device.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
#define BOOT_ADDR 0x1FFF0000 // my MCU boot code base address
#define USB_RX_BUF_SIZE 512
#define DFU_BOOT_REQ 0xAA
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
volatile uint8_t usb_rx_buffer[USB_RX_BUF_SIZE];
volatile uint32_t usb_rx_count = 0; // number of bytes in buffer
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
/* USER CODE BEGIN PFP */
void JumpToBootloader(void);
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_USB_DEVICE_Init();
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
uint32_t now = 0, next_blink = 100;
while (1) {
now = uwTick;
if (now >= next_blink) {
HAL_GPIO_TogglePin(STATUS_LED_GPIO_Port, STATUS_LED_Pin);
next_blink = now + 100;
}
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
/** Configure the main internal regulator output voltage
*/
if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1) != HAL_OK)
{
Error_Handler();
}
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI48|RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSI48State = RCC_HSI48_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLM = 1;
RCC_OscInitStruct.PLL.PLLN = 10;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7;
RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief GPIO Initialization Function
* @PAram None
* @retval None
*/
static void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(STATUS_LED_GPIO_Port, STATUS_LED_Pin, GPIO_PIN_RESET);
/*Configure GPIO pin : STATUS_LED_Pin */
GPIO_InitStruct.Pin = STATUS_LED_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(STATUS_LED_GPIO_Port, &GPIO_InitStruct);
/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}
/* USER CODE BEGIN 4 */
struct boot_vectable_ {
uint32_t Initial_SP;
void (*Reset_Handler)(void);
};
#define BOOTVTAB ((struct boot_vectable_ *)BOOT_ADDR)
void JumpToBootloader(void)
{
/* Disable all interrupts */
__disable_irq();
// Reset USB
// USB->CNTR = 0x0003;
/* Disable Systick timer */
SysTick->CTRL = 0;
/* Set the clock to the default state */
HAL_RCC_DeInit();
// HAL_DeInit();
/* Clear Interrupt Enable Register & Interrupt Pending Register */
for (uint8_t i = 0; i <= 7; i++)
{
NVIC->ICER[i]=0xFFFFFFFF;
NVIC->ICPR[i]=0xFFFFFFFF;
}
/* Re-enable all interrupts */
__enable_irq();
// Set the MSP
__set_MSP(BOOTVTAB->Initial_SP);
// Jump to app firmware
BOOTVTAB->Reset_Handler();
}
void USB_CDC_RxHandler(uint8_t* Buf, uint32_t Len)
{
// accumulate incoming USB data into the buffer
if ((usb_rx_count + Len) < USB_RX_BUF_SIZE) {
memcpy((uint8_t *)&usb_rx_buffer[usb_rx_count], Buf, Len);
usb_rx_count += Len;
}
if (usb_rx_buffer[0] == DFU_BOOT_REQ)
{
JumpToBootloader();
}
}
/* USER CODE END 4 */
/**
* @brief This function is executed in case of error occurrence.
* @retval None
*/
void Error_Handler(void)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
__disable_irq();
while (1)
{
}
/* USER CODE END Error_Handler_Debug */
}
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @PAram file: pointer to the source file name
* @PAram line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t *file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
In JumpToBootloader, I did add a few lines that people in the comments had mentioned but it still did not work...
// Reset USB
// USB->CNTR = 0x0003;
// HAL_DeInit();
This was from the response by EThom.3 who was also using the STM32L4
