Can't jump from bootloader to application on stm32l072cz that has cortex m0+

[Kabde]

Hi,

I am writing a customized bootloader for STM32L072CZ (Cortex M0+) and I have an issue with performing the jumping from the bootloader to the application.

My application is linked at certain address (0x800b000) and I want to jump to this address from the bootloader. I've looked into a lot of online discussions but mainly for different stm32 processors.

Here is my code to do the jumping:

void mbed_start_application(uint32_t address) {

 __disable_irq();

 SysTick->CTRL = 0;

 // Disable IRQs & clear pending IRQs

 int i;

 for (i = 0; i < 8; i++) {

  NVIC->IP[i] = 0x00000000;

 }

 NVIC->ICER[0] = 0xFFFFFFFF;

 NVIC->ICPR[0] = 0xFFFFFFFF;

 // SCB->CPUID  - Read only CPU ID register

 SCB->ICSR |= SCB_ICSR_PENDSVCLR_Msk;

 SCB->VTOR = address;

 SCB->AIRCR = 0x05FA | 0x0000;

 SCB->SCR = 0x00000000;

 for (i = 0; i < 2; i++) {

    SCB->SHP[i] = 0x00;

 }

 SCB->SHCSR = 0x00000000;

 HAL_DeInit();

 /*GPIO_DeInit();

 HAL_RCC_DeInit();

 HAL_MPU_Disable();*/

 __set_MSP(*(__IO uint32_t*)address);

 /* Launch application */

 uint32_t JumpAddress = *(__IO uint32_t*)(address + 4u);

 pFunction Jump = (pFunction)JumpAddress;

 Jump();

}

Please point what I could be missing .

Thanks,

Khaled

[Uwe Bonnes]

It is best to have a switch very early in the boot code before any initialization. That switch should look for a magic number in RAM that has not yet been initialized. If it sees the magic number, the number is reset and a jump to bootloader with setting Sysmen, vtor msp etc is done. User code , when boot loader is requested, sets that magic number and performs a warm reset.

[Kabde]

Thanks for your answer Uwe but I would appreciate if you clarify what you mean. It's not clear for me what you mean by early switch and magic number in the RAM. Thanks!

[Uwe Bonnes]

Early in the boot code you test some RAM at known address for a know number (magic number). If the magic number is read, you branch (switch) to the code calling the system bootloader otherwise you proceed with your code.

Otherwise I do not see SYSCFG_CFGR1 set to 01. Maybe that is what is missing from your code.

[Tesla DeLorean]

Who will enable the interrupt you disabled?

What about the code on the app side using the correct vector table?

It is not jumping? Have you traced execution?

>>I've looked into a lot of online discussions but mainly for different stm32 processors.

The real problem is the shot-gun/kitchen-sink approach, and not really understanding the problem or the processor properly.

Or the interactions/expectations of the code on either side.