STM32 Enter DFU from VCP

[McNickel]

Hello,

I have an application where I would like to switch the STM32G431KB into the built-in bootloader (using USB DFU) by sending a specific byte through the CDC Virtual COM port. I was able to get the unit into DFU mode by running the "USB_BootloaderInit" function below when a button is pressed, however when I try running the function upon reception of data from the CDC port, Windows either does not see the device or gives me a "Device Descriptor Request Failed" notification.

I get the feeling the USB port is still doing some work or there are interrupts still running, but I am not sure how to go about checking what is going on or properly clearing any pending interrupts, or what exactly is going on and I wanted to see if anyone could help point me in the right direction.

This is the function that allows me to enter into the bootloader:

void USB_BootloaderInit()
{
	volatile uint32_t addr = 0x1FFF0000;
	SysMemBootJump = (void (*)(void)) (*((uint32_t *)(addr + 4)));	//Point the PC to the System Memory reset vector
 
	HAL_RCC_DeInit();		//Reset the system clock
	SysTick->CTRL = 0;		//Reset the  SysTick Timer
	SysTick->LOAD = 0;
	SysTick->VAL  = 0;
 
	__set_MSP(*(uint32_t *)addr);
 
	SysMemBootJump();
 
	while(1);
}

It is being called when the correct character is received through the CDC_Receive_FS function as part of the CubeIDE USB Device Middleware.

Currently, I have tried running the USBD_DeInit and USBD_Stop functions before the USB_BootloaderInit function, along with putting some delay (5ms - 1Second using timers) between the DeInit/Stop and BootloaderInit functions, with no avail.

Any help is appreciated

[Uwe Bonnes · Accepted solution]

You need to set VTOR an SYSCFG MEMMODE. But better is to have a switch in early startup code to check for some magicnumber in RAM that you set just before reset when DFU is requested.

[TDK]

You can reset the USB peripheral using code similar to:

  // disable USB
  __HAL_RCC_USB_OTG_FS_CLK_ENABLE();
  __HAL_RCC_OTGFS_FORCE_RESET();
  __HAL_RCC_OTGFS_RELEASE_RESET();

[McNickel]

Thank you Uwe Bonnes,

I had been thinking about putting a statement in early startup, but I wasn't sure how to go about it so I was avoiding it, but it worked flawlessly.

For anyone who is reading this in the future, here is what I did:

When the correct character is received on the serial port, I run the following function:

void USB_TriggerBootloader()
{
	SYSCFG->MEMRMP &= 0xFFFFFFF9;		//Remap the memory (may not be necessary)
	SYSCFG->MEMRMP |= 1;
	switchToBootloader = 0x11;			//Set the noinit variable to be read by startup code
	NVIC_SystemReset();					//Reset the system
}

the switchToBootloader variable is defined as:

uint8_t switchToBootloader __attribute__ ((section (".noinit")));

The ".noinit" prevents the variable from being re-initialized upon a reset.

After a reset, the first lines of code in the main function are an if statement which checks switchToBootloader and, if it is equal to 0x11, runs the following function:

void (*SysMemBootJump) (void);
 
void USB_BootloaderInit()
{
	switchToBootloader = 0x00;	//Reset the variable to prevent being stuck in the bootloader (since a device reset wont change it)
	volatile uint32_t addr = 0x1FFF0000;	//The STM32G431KB system memory start address
	SysMemBootJump = (void (*)(void)) (*((uint32_t *)(addr + 4)));	//Point the PC to the System Memory reset vector
 
	HAL_RCC_DeInit();		//Reset the system clock
	SysTick->CTRL = 0;		//Reset the  SysTick Timer
	SysTick->LOAD = 0;
	SysTick->VAL  = 0;
 
	__set_MSP(*(uint32_t *)addr);	//Set the Main Stack Pointer
 
	SysMemBootJump();				//Run our virtual function defined above that sets the PC
 
	while(1);
}

And it works reliably!

EDIT: I added the declaration for SysMemBootJump.

[Davorin]

How did you define SysMemBootJump?

Otherwise gives me:

error: called object 'SysMemBootJump' is not a function or function pointer

 Update: Never mind...fund it (o;

[Davorin]

Still no luck with your code...

It does reset and the switchToBootloader is still set to 0x11....but after USB_BootloaderInit() the device is gone.

Guess something to do with the SYSCFG remapping....

SYSCFG->MEMRMP doesn't exist for the STM32F0 family...

Guess it must be SYSCFG_CFGR1_MEM_MODE then...

[McNickel]

Check out AN2606, read the section for the device you are using and also read section 64 to get the system memory address for that device (set “addr�? to the first address listed in the system memory column for the device)

AN2606:

https://www.st.com/resource/en/application_note/cd00167594-stm32-microcontroller-system-memory-boot-mode-stmicroelectronics.pdf

[Davorin]

The appnote only tells that BOOT0 pin has to be set high.....and I already had the sys mem address correct with 0x1FFFC800.

Now hooked up my Nucleo-G431 board and used your code here....and connected USB via PA11/PA12...

When it hits USB_BootloaderInit() after reset....I don't even see a message then trying to enumerate the bus...

int main(void)
{
......
......
  if(switchToBootloader == 0x11)
  {
	  HAL_Delay(2000);
	  char text[20] = "Switching to DFU\n\r";
	  CDC_Transmit_FS((uint8_t *)text, 18);
	  USB_BootloaderInit();
  }
 
  while (1)
  {
    /* USER CODE END WHILE */
 
    /* USER CODE BEGIN 3 */
	  if(send_usb)
	  {
		  HAL_RTC_GetTime(&hrtc, &currTime, RTC_FORMAT_BIN);
		  HAL_RTC_GetDate(&hrtc, &currDate, RTC_FORMAT_BIN);
 
		  sprintf(buffer,"%02d.%02d.20%02d %02d:%02d:%02d\n\r", currDate.Date, currDate.Month, currDate.Year, currTime.Hours, currTime.Minutes, currTime.Seconds);
 
		  CDC_Transmit_FS((uint8_t *)buffer, 21);
	  	  send_usb = 0;
	  	  counter++;
	  	  if(counter > 10)
	  		USB_TriggerBootloader();
	  }
  }
}
 
/* USER CODE BEGIN 4 */
void HAL_RTC_AlarmAEventCallback(RTC_HandleTypeDef *hrtc)
{
//	HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
	send_usb = 1;
}
 
void USB_TriggerBootloader()
{
	SYSCFG->MEMRMP &= 0xFFFFFFF9;		//Remap the memory (may not be necessary)
	SYSCFG->MEMRMP |= 1;
	switchToBootloader = 0x11;			//Set the noinit variable to be read by startup code
	NVIC_SystemReset();					//Reset the system
}
 
void (*SysMemBootJump) (void);
 
void USB_BootloaderInit()
{
	switchToBootloader = 0x00;	//Reset the variable to prevent being stuck in the bootloader (since a device reset wont change it)
	volatile uint32_t addr = 0x1FFF0000;	//The STM32G431KB system memory start address
	SysMemBootJump = (void (*)(void)) (*((uint32_t *)(addr + 4)));	//Point the PC to the System Memory reset vector
 
	HAL_RCC_DeInit();		//Reset the system clock
	SysTick->CTRL = 0;		//Reset the  SysTick Timer
	SysTick->LOAD = 0;
	SysTick->VAL  = 0;
 
	__set_MSP(*(uint32_t *)addr);	//Set the Main Stack Pointer
 
	SysMemBootJump();				//Run our virtual function defined above that sets the PC
 
	while(1);
}
/* USER CODE END 4 */

[McNickel]

I will take a deeper look at your code in a bit, but the first thing i notice: try removing lines 7 - 9 ( The delay and CDC transmit). I had to add the whole reset part because I was only seeing an error when it was triggered by USB, so i presume there is maybe an interrupt or a task that hasn't been cleared that is causing the issue.

Do the CDC functions work correctly? Are you getting data to/from the computer?

EDIT: also make sure the if switchToBootloader statement, line 5, is the absolute first piece of code in your main function, prior to all of the initializations.

[Davorin]

Okay...will have a deeper look tomorrow morning (o;

Well for the CDC functions...it sends every second the RTC date/time out without problems....though there is no code yet for receiving...

You mean that switchToBootloader part has to come even before the pre-defined HAL initializations?

Ah that might cause the problem...

Well would be great if that was it so I can soon publish my programmable thermocouple USB logger hard/software project on github for everyone (o;

Will keep you updated...

many thanks

richard