sorry for bothering you but know i know what is the problem when i enable the external loader my code stuck here :
static void prvPortStartFirstTask( void )
{
/* Start the first task. This also clears the bit that indicates the FPU is
in use in case the FPU was used before the scheduler was started - which
would otherwise result in the unnecessary leaving of space in the SVC stack
for lazy saving of FPU registers. */
uint32_t r0_val, msp_val, control_val;
// Manually set the VTOR to the RAM address where the vector table is expected
SCB->VTOR = 0x24000004; // Adjust this if your vector table starts at a different address
printf("Manually setting VTOR to: %08X\n", SCB->VTOR);
// Read the first entry of the vector table to get the initial MSP value
r0_val = *(volatile uint32_t *)(SCB->VTOR);
printf("Initial MSP Value from Vector Table: %08X\n", r0_val);
if (r0_val == 0 || r0_val == 0xFFFFFFFF) {
// Fallback to a default stack address within RAM
printf("Invalid MSP value, manually setting to a safe address.\n");
r0_val = 0x24080000; // Example: Adjust to a valid address in your RAM.
}
msp_val = r0_val; // Use this value as the initial MSP
__asm volatile("msr msp, %0" : : "r" (msp_val));
// Clear CONTROL register to switch to Main Stack Pointer
control_val = 0;
__asm volatile("msr control, %0" : : "r" (control_val));
printf("Control Register Set to: %08X\n", control_val);
// Enable interrupts and make a system call to start the first task
__asm volatile(
"cpsie i \n" // Globally enable interrupts.
"cpsie f \n"
"dsb \n"
"isb \n"
"svc 0 \n" // System call to start first task.
"nop \n"
);
// __asm volatile(
// " ldr r0, =0xE000ED08 \n" /* Use the NVIC offset register to locate the stack. */
// " ldr r0, [r0] \n"
// " ldr r0, [r0] \n"
// " msr msp, r0 \n" /* Set the msp back to the start of the stack. */
// " mov r0, #0 \n" /* Clear the bit that indicates the FPU is in use, see comment above. */
// " msr control, r0 \n"
// " cpsie i \n" /* Globally enable interrupts. */
// " cpsie f \n"
// " dsb \n"
// " isb \n"
// " svc 0 \n" /* System call to start first task. */
// " nop \n"
// );
}
this is from freertos code and i ask chat gpt to make me some printfs on it to determine the problem and i commented the original code at the bottom of the funciton and this is what i get when the external loader is
enabled :
Initial NVIC VTOR Address: 24000200
Initial MSP Value from Vector Table: 00000000
Invalid MSP value, manually setting to a safe address.
and if i disable the external loader the code runs normally and this is what i get from the printfs :
Initial NVIC VTOR Address: 08000000
Initial MSP Value from Vector Table: 24080000
Control Register Set to: 00000000
it seems like that when i enable the external loader it corrupts the stack pointer, and the vector table even without uploading any code to the external flash ,thanks in advance.
