编写BOOT程序，和APP程序。
BOOT程序检查OTA参数，执行OTA升级，然后跳转到APP代码。

记录一下跳转APP需要修改得东西：

1、BOOT程序 修改跳转地址

先检查APP地址是否有效
然后关闭外设 反初始化
设置MSP指针，进行跳转

/**
 * @brief  Jump from boot to app function.
 * @param  [in] u32Addr                 APP address
 * @retval LL_ERR                       APP address error
 */
int32_t IAP_JumpToApp(uint32_t u32Addr)
{
    uint32_t u32StackTop = *((__IO uint32_t *)u32Addr);
	uint32_t JumpAddr;
	func_ptr_t JumpToApp;
	
    /* Check stack top pointer. */
    if ((u32StackTop > SRAM_BASE) && (u32StackTop <= (SRAM_BASE + 0x010000UL))) {
        IAP_PeriphDeinit();
        /* Jump to user application */
        JumpAddr = *(__IO uint32_t *)(u32Addr + 4U);
        JumpToApp = (func_ptr_t)JumpAddr;
        /* Initialize user application's Stack Pointer */
        __set_MSP(u32StackTop);
        JumpToApp();
    }

    return LL_ERR;
}

2、APP程序修改起始地址

修改VECT_TAB_OFFSET定义值 与BOOT对应

/**
 * @brief  Setup the microcontroller system. Initialize the System and update
 *         the SystemCoreClock variable.
 * @param  None
 * @retval None
 */
void SystemInit(void)
{
    /* FPU settings */
#if (__FPU_PRESENT == 1) && (__FPU_USED == 1)
    SCB->CPACR |= ((3UL << 20) | (3UL << 22)); /* set CP10 and CP11 Full Access */
#endif
    SystemCoreClockUpdate();
#if defined (ROM_EXT_QSPI)
    SystemInit_QspiMem();
#endif /* ROM_EXT_QSPI */
    /* Configure the Vector Table relocation */
    SCB->VTOR = VECT_TAB_OFFSET;    /* Vector Table Relocation */
}

3、APP程序修改内存加载文件

如下图，如果不勾选该项，则要手动修改ACT文件的LR_IROM1区的起始地址和结束地址
如果勾选，则要在target选项中设置起始地址和结束地址

ACT文件一般格式：

; ****************************************************************
; Scatter-Loading Description File
; ****************************************************************
LR_IROM1 0x00004000 0x00040000  {    ; load region size_region
    ER_IROM1 0x00004000 0x00040000  {  ; load address = execution address
        *.o (RESET, +First)
        *(InRoot$$Sections)
        .ANY (+RO)
        .ANY (+XO)
    }
    RW_IRAM1 0x1FFF8000 UNINIT 0x00000008  {  ; RW data
        *(.bss.noinit)
    }
    RW_IRAM2 0x1FFF8008 0x0000FFF8  {  ; RW data
        .ANY (+RW +ZI)
        .ANY (RAMCODE)
    }
    RW_IRAMB 0x200F0000 0x00001000  {  ; RW data
        .ANY (+RW +ZI)
    }
}