How to make an own dfu application on STM32F746G-DISCO board?

Question

I'm trying to make own dfu application on STM32F746G-DISCO board.

I've already tested dfu function by using ST's DFU_Standalone demo example which is worked under USB device mode.

Demo example is also provided upgradable sample application which is named as STM32746G_DISCOVERY_SysTick_0x08008000.dfu.

I can upgrade this application by using DfuSeDemo.exe on windows 10 PC and It works well.

But if i made a simple led toggle dfu application, It cannot run.

In this case, i have used the same DFU bootloader. Just changed application.

Below is what i modified for dfu application

--------------------------------------------------------------------------------

1. Changed app's flash location to 0x08008000 in STM32F746NGHX_FLASH.ld

2. Changed VECT_TAB_OFFSET to 0x8000 in system_stm32f7xx.c.

the board is always running in DFU mode even if there is no error by using DfuFileMgr.exe and DfuSeDemo.exe

So i checked flash's USBD_DFU_APP_DEFAULT_ADD(0x08008000) location by using STM32CubeProgrammer.

It shows 0x20050000. Obviously, this value cannot meet in DFU bootloader's application jump condition.

/* Test if user code is programmed starting from USBD_DFU_APP_DEFAULT_ADD address */

if(((*(__IO uint32_t*)USBD_DFU_APP_DEFAULT_ADD) & 0x2FFE0000 ) == 0x20000000)

{

/* Jump to user application */

JumpAddress = *(__IO uint32_t*) (USBD_DFU_APP_DEFAULT_ADD + 4);

JumpToApplication = (pFunction) JumpAddress;

/* Initialize user application's Stack Pointer */

__set_MSP(*(__IO uint32_t*) USBD_DFU_APP_DEFAULT_ADD);

JumpToApplication();

}

Could you let me know what i missed something?

Thanks in advance,

Tesla DeLorean · Accepted Answer

The RAM stack test can be changed/broadened, one can also report one value in Initial SP, and then load a higher value within the Reset Handler.

The DFU file contains address/size location, so the the ROM based loader can replace the App or the User Loader, or any combinations thereof.

Watch generally that you don't have any active IRQs with different memory/structure expectations that won't handle the transfer of control

Uwe Bonnes · Answer

Why do you want to write your own DFU application. For USB1, a DFU application is in the system bootloader. Have some switch early in your startup code to run DFU with some marker, e.g. some magic in RAM or some reset event. When the application should switch to DFU, set this marker and reset, Only if you want DFU for USB2, you need your own DFU code.

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