使用STM32F042K6从用户代码跳转到系统引导加载程序

Question

编辑：为了devan的解决方案，我设法用STM32F042K6从用户代码跳转系统引导程序。

boot.h

/* boot.h */
#include "stm32f0xx_hal.h"

#if defined(STM32F042x6) || defined(STM32F048xx) 
    #define SYSTEM_MEMORY_ADDRESS       0x1FFFC400
#elif defined(STM32F070xB)
    #define SYSTEM_MEMORY_ADDRESS   0x1FFFC800
#elif defined(STM32F070x6)
    #define SYSTEM_MEMORY_ADDRESS       0x1FFFC400
#endif

HAL_StatusTypeDef SystemBootloaderJump(void);

boot.c

/* boot.c */
#include "boot.h"

/* I just re-write this code -> https://electronics.stackexchange.com/questions/312303/stm32f091-jump-to-bootloader-from-application */
HAL_StatusTypeDef SystemBootloaderJump(void)
{
    typedef void (*pFunction)(void);
    pFunction JumpToApplication;

    __HAL_RCC_USART1_FORCE_RESET();
    HAL_Delay(5);
    __HAL_RCC_USART1_RELEASE_RESET();
    HAL_Delay(5);

    HAL_RCC_DeInit();

    SysTick->CTRL = 0;
    SysTick->LOAD = 0;
    SysTick->VAL = 0;

    /**
     * Step: Disable all interrupts
     */
    __disable_irq();

    /* ARM Cortex-M Programming Guide to Memory Barrier Instructions.*/
    __DSB();

    __HAL_SYSCFG_REMAPMEMORY_SYSTEMFLASH();

    /* Remap is bot visible at once. Execute some unrelated command! */
    __DSB();
    __ISB();

    /** Get option bytes. 
        *   More info at -> RM0091 Reference manual STM32F0x1/STM32F0x2/STM32F0x8 advanced ARM®-based 32-bit MCUs
        *   4 Option byte 
        *           There are up to 8 option bytes. They are configured by the end user depending on the
        *       application requirements. 
        *       ...
        *       ...
        *           4.1 Option byte description
        *               4.1.1 User and read protection option byte
        *                   Flash memory address: 0x1FFF F800
        *                   ...
        *                   Bits 23:16 USER: User option byte (stored in FLASH_OBR[15:8])
        *                       Bit 23: BOOT_SEL
        *                           0: BOOT0 signal is defined by nBOOT0 option bit
        *                           1: BOOT0 signal is defined by BOOT0 pin value (legacy mode)
        *                       Available on STM32F04x and STM32F09x devices only. Considered as “1” on other devices.
        *                       ...
        *                       ...
        *                       Bit 19: nBOOT0
        *                       When BOOT_SEL is cleared, nBOOT0 bit defines BOOT0 signal value used to select the
        *                       device boot mode. Refer to Section 2.5: Boot configuration for more details.
        *                       Available on STM32F04x and STM32F09x devices only.
        */
    FLASH_OBProgramInitTypeDef pOBInit;
    /* Get the Option byte configuration */
    HAL_FLASHEx_OBGetConfig(&pOBInit);

    /* BOOT_SEL = 0 */
    pOBInit.USERConfig &= ~(OB_BOOT_SEL_SET);
    /* nBOOT0=1 */
    pOBInit.USERConfig |= OB_BOOT0_SET;


    /** HAL_FLASHEx_OBProgram && HAL_FLASHEx_OBErase
      * HAL_FLASH_OB_Unlock() should be called before to unlock the options bytes
      */
    if(HAL_FLASH_OB_Unlock() != HAL_OK)
    {
        return HAL_ERROR;
    }

    /*We need to erase option bytes before write. */
    if(HAL_FLASHEx_OBErase() != HAL_OK)
    {
        return HAL_ERROR;
    }

    /* Write changed option bytes */
    if(HAL_FLASHEx_OBProgram(&pOBInit))
    {
        return HAL_ERROR;
    }

    JumpToApplication = (void (*)(void)) (*((uint32_t *) ((SYSTEM_MEMORY_ADDRESS + 4))));

    /* Initialize user application's Stack Pointer */
    __set_MSP(*(__IO uint32_t*) SYSTEM_MEMORY_ADDRESS);

    JumpToApplication();
    return HAL_OK;
}

---

如何在擦除闪存页后重置STM32微控制器？

我的目标是使用STM32F042K6微控制器从用户闪存跳转系统引导程序。但在AN2606应用笔记STM32单片机系统内存启动模式下其说;

由于此产品上存在空检查机制，因此无法从用户代码跳转到系统引导加载程序。这种跳转将导致跳回用户闪存空间。但是如果用户闪存的前4个字节（在0x0800 0000）在跳转时为空（即在跳转之前擦除第一个扇区或在闪存为空时从SRAM执行代码），则跳转到时将执行系统引导加载程序。

所以，我将我的函数（除了main（））放在ROM 0x08007C00 - 0x08007FFF（我的闪存的最后一页）中。在我的主要功能中，我正在调用擦除功能 - 位于我的微控制器闪存和擦除第一页的最后一页。它会成功擦除第一页但在此之后我无法在软件中重置我的微控制器或无法跳转到系统引导程序。微控制器卡在某处，但我找不到。但是当我用复位引脚复位微控制器时，它会从系统引导程序引导。这意味着如果我能以某种方式重置微控制器，我将实现我的目标。

我打开其他解决方案。我的代码就是这样;

/* main.c located at 0x0800 0000 - 0x0800 7BFF */
int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART1_UART_Init();
  MX_TIM16_Init();

  StartBoot();

  while(1){}
 }

---

/* boot.c located at 0x0800 7C00 - 0x0800 7FFF */

#define ADDR_FLASH_PAGE_0     ((uint32_t)0x08000000) /* Base @ of Page 0, 1 Kbyte */

void StartBoot(void)
{
    if(ErasePage(ADDR_FLASH_PAGE_0) == HAL_OK)
    {
        HAL_FLASH_Lock();
        NVIC_SystemReset();
    }
}

HAL_StatusTypeDef ErasePage(uint32_t address)
{
/* Unlock the Flash to enable the flash control register access */
  HAL_FLASH_Unlock();

  /* Erase the user Flash area */

  /* Fill EraseInit structure*/
  EraseInitStruct.TypeErase   = FLASH_TYPEERASE_PAGES;
  EraseInitStruct.PageAddress = address;
  EraseInitStruct.NbPages     = 1; /* Erase 1 Page */

  /* Note: If an erase operation in Flash memory also concerns data in the data or instruction cache,
     you have to make sure that these data are rewritten before they are accessed during code
     execution. If this cannot be done safely, it is recommended to flush the caches by setting the
     DCRST and ICRST bits in the FLASH_CR register. */
  if (HAL_FLASHEx_Erase(&EraseInitStruct, &PAGEError) != HAL_OK)
  {
    /*
      Error occurred while page erase.
      User can add here some code to deal with this error.
      PAGEError will contain the faulty page and then to know the code error on this page,
      user can call function 'HAL_FLASH_GetError()'
    */
        HAL_FLASH_Lock();
        return HAL_ERROR;

  }
    return HAL_OK;
}

Answer 1

该应用笔记指导有点奇怪。我使用过STM32F042系列，特别是STM32F042K6。我的经验是，与其他STM32系列器件相比，唯一奇怪的行为是引导加载程序在运行时强制执行BOOT_SEL位，而不仅仅是芯片从复位启动时。

BOOT0状态的运行时检查通常会导致它跳回主闪存，即使您手动重新映射内存并像其他STM32系列部件一样跳转到引导加载程序。

要解决此问题，您可以在选项字节中设置BOOT_SEL=0和nBOOT0=1，以便在启动时始终引导至主闪存，如下表所示：

以这种方式设置选项字节后，您可以采用已经覆盖几次的正常remap-memory-and-jump-to-the-bootloader方法。

（注意：STM32F042系列引导存储器位于0x1FFFC400，而不是STM32F072示例中所示的0x1FFFC800）。

请注意，禁用BOOT引脚检查将阻止您使用BOOT引脚强制芯片进入引导加载程序。您可能需要添加自己的软件检查以在引导期间提前读取BOOT0引脚并跳转到引导加载程序。