Atmel SAM4E Bootloader/VTOR executing new application

Hello everyone!

I am also trying to write my own bootloader, so I am facing similar problems dealt in this post.

One good question would be, when am I able to modify the VTOR? I say this because I init the bootloader as a normal application with its Interrupt Vector Table, and being the reset vector in 0x0000_0000, I pretend to do all the bootloader stuff and after finishing, modify VTOR register and jump to 0x0000_2000 (the bootloader has been configured with BOOTPROT 2, so 8K memory has been "protected" for this purpose). Is this possible? It is not working right now. I tried to modify VTOR before and after initializing the board (ATMEL R21 with a ARM CORTEX M0+).

In order to modify the VTOR I do it like this:

SCB->VTOR = ((uint32_t)0x00002000);

But being the VTOR just from 32:7 won't it be better to do it like this?

SCB->VTOR = ((uint32_t)0x00002000 << (SCB_VTOR_TBLOFF_Pos - 1)); // shift 7 to the left ARM Information Center

After doing this (that is nor working), I pretend to jump to the application so... which considerations should I bear in mind? Would be enough just with a jump to the 0x0000_2000 address?

void start_application( uint32_t app_link_location )

{

   asm(" blx r0");

}

Because I have seen in other posts code like this inside the function:

asm(" ldr r1, [r0,#0]"); // get the stack pointer value from the program's reset vector

asm(" mov sp, r1");      // copy the value to the stack pointer asm(" ldr r0, [r0,#4]"); // get the program counter value from the program's reset vector

asm(" mov r0, #0");

asm(" blx r0");          // jump to the start address

or even something like this avoiding the assembly:

void jump_to_application( void )

{

  typedef int(*fn_prt_t)(void);

  fn_prt_t main_prog;

  main_prog= (fn_prt_t)0x00002000;

  main_prog();

}

I would really appreciate any advice.

Best regards,

Iván

Hello everyone!

I am also trying to write my own bootloader, so I am facing similar problems dealt in this post.

One good question would be, when am I able to modify the VTOR? I say this because I init the bootloader as a normal application with its Interrupt Vector Table, and being the reset vector in 0x0000_0000, I pretend to do all the bootloader stuff and after finishing, modify VTOR register and jump to 0x0000_2000 (the bootloader has been configured with BOOTPROT 2, so 8K memory has been "protected" for this purpose). Is this possible? It is not working right now. I tried to modify VTOR before and after initializing the board (ATMEL R21 with a ARM CORTEX M0+).

In order to modify the VTOR I do it like this:

SCB->VTOR = ((uint32_t)0x00002000);

But being the VTOR just from 32:7 won't it be better to do it like this?

SCB->VTOR = ((uint32_t)0x00002000 << (SCB_VTOR_TBLOFF_Pos - 1)); // shift 7 to the left ARM Information Center

After doing this (that is nor working), I pretend to jump to the application so... which considerations should I bear in mind? Would be enough just with a jump to the 0x0000_2000 address?

void start_application( uint32_t app_link_location )

{

   asm(" blx r0");

}

Because I have seen in other posts code like this inside the function:

asm(" ldr r1, [r0,#0]"); // get the stack pointer value from the program's reset vector

asm(" mov sp, r1");      // copy the value to the stack pointer asm(" ldr r0, [r0,#4]"); // get the program counter value from the program's reset vector

asm(" mov r0, #0");

asm(" blx r0");          // jump to the start address

or even something like this avoiding the assembly:

void jump_to_application( void )

{

  typedef int(*fn_prt_t)(void);

  fn_prt_t main_prog;

  main_prog= (fn_prt_t)0x00002000;

  main_prog();

}

I would really appreciate any advice.

Best regards,

Iván