M0 in-line assembler moving from bootloader to main app

[DiBosco]

Folks,

I have a bootloader for an M0 which works without using interrupts. It works in that it loads the new app, the CRC in the new app matches and I then try and jump to 0x8004000.

In the past I have used a couple of different methods with M3/4 to boot to the app from bootloader dependent on what compiler/IDE I was using, but the M0 is slightly different due to how the vector table is not relocatable. So we've come up with a method to get round that and "all" I need to do is jump to 0x8004000.

I *think I need something like this:

void jump_to_normal_application(void)
{

    u32 jump_address;

    jump_address = *(volatile u32*) (MAIN_PROG_START_ADDRESS + 4);
    jump_to_application = (pFunction) jump_address;

    asm("ldr sp, =0x20002000");

    jump_to_application();

}

I'm getting the error:

Error: lo register required -- `ldr sp,=0x20002000'

I've searched this and although I can find many hits  I can't see anything vaguely relevant to my situation.

Also, I would like to make 0x20002000 on line 9 top be a #define or loading from a C variable

Can anyone help me with this please? __Set_MSP is not available to me due to the, errr, "individual" setup I am forced to use.

What is the way to do this and are any of my assumptions above even vaguely correct? Am using gcc.

[wegi01]

This is super ultra simple things - running MCU from required address in assembler - much more you make self tired by adding so many definitions and typecastings in C.

Without problem should be working in depends what is under 0x08004004 - pointer to running program or immediatelly code - so you know before how to treat it - I'd show. Go back here and tell to as "IT WORK"

[Tesla DeLorean]

Ok, fair enough

What's at 0x08004000 ? Executable code or an indirect address to an entry point?

  .word EntryPoint ; 32-bit pointer to function

or

 .thumb_func
 .global EntryPoint
 .type   EntryPoint, %function

  ldr r0, =0x20002000
  movs sp, r0
...
 .size EntryPoint, .-EntryPoint

or

void EntryPoint(void)
{
...
}

[wegi01]

@DiBosco When I sometimes want to look to value I use my small function which convert data from R1 register to ASCII HEX string to buffer pointed in R0 register.
Declaration in C looks:

extern void my_htoa32(char * buf, uint32_t data);

But if you want invoke this from assembler you should to do:

     ldr r0, = 0x20000369 // for example a free area for use as buffer 11 bytes
     ldr r1, = 0x42408200 // value for tested
     BL  my_htoa32
 lll:
     b lll  // neverending loop

Function my_htoa32:

    .syntax unified
    .cpu cortex-m0
    .fpu softvfp
    .thumb

    .thumb_func
    .global my_htoa32
    .type   my_htoa32, %function


    .text
//----------------

//======================================================
// HEX 32BIT value convert to string
//====================================
       // INPUT:
       //    R0, =  ; POINTER TO OUTPUT char DATA BUFFER
       //    R1, =  ; VALUE TO HEXADECIMAL CONVERT

       // output: no output, data in buffer are output
//=======================================================
//=========================
my_htoa32:

        MOV    R3, 0x7830     // "0x"
        STRH   R3, [R0]       // STORE "0x" TO BUFFER
        MOVS   R3, 2          // output data 2 bytes after start buffer
//--
LP01:
        LSRS   R2, R1, #28    // R2 = OUR DATA TO STRING CONVERT 1 BYTE = NYBBLE 0..F
        LSLS   R1, R1, #4     // R1 * 16 = R1 << 4
        ADDS   R2, R2, #0x30  // CONVERT TO NUMBER
        CMP    R2, #0x3A
        BCC    LP01A          // if data < than 0x3a don't  add #7
        ADDS   R2,R2, 0x07    // CONVER TO LETTER
LP01A:
        STRH   R2, [R0, R3]   // STRH store byte and zero terminated
        ADDS   R3, R3, #1
        CMP    R3, #10
        BNE    LP01
//---
        BX     LR
//=============================================================

The result you can observe in STM32 Link Utility or in Cube Programmer: