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When trigger the PendSV exception, the context switches with Cortex-M0 is wrong. but the program without the bootloader, the app can run ok.
Most likely the vector table is not correct. The M0 does not allow remapping of the vector table and perhaps with bootloader it is expecting that it can.
Check your bootloader to see how it does the vector table remapping and make sure your chip supports this.
I found that LR is wrong,when it run out from PendSV_handler of the app. I try to save the LR. but I do konw how to do this.
The code of the boot :
void PendSV_Handler(){// uint32_t address;// __asm("PUSH {R14}\n");// address=FLASH_OFFSET+4*14; (*(void(*)(void))(*(uint32_t*) 0x2038))();// __asm("POP {R0}\n"); // __asm("LDR 0x1213223\n");}
the app code :
PendSV_Handler CPSID I ; Prevent interruption during context switch MRS R0, PSP ; PSP is process stack pointer
CMP R0, #0 BEQ OS_CPU_PendSVHandler_nosave ; equivalent code to CBZ from M3 arch to M0 arch ; Except that it does not change the condition code flags
SUBS R0, R0, #0x10 ; Adjust stack pointer to where memory needs to be stored to avoid overwriting STM R0!, {R4-R7} ; Stores 4 4-byte registers, default increments SP after each storing SUBS R0, R0, #0x10 ; STM does not automatically call back the SP to initial location so we must do this manually
LDR R1, =OSTCBCur ; OSTCBCur->OSTCBStkPtr = SP; LDR R1, [R1] STR R0, [R1] ; R0 is SP of process being switched out
; At this point, entire context of process has been savedOS_CPU_PendSVHandler_nosave PUSH {R14} ; Save LR exc_return value LDR R0, =OSTaskSwHook ; OSTaskSwHook(); BLX R0 POP {R0} MOV R14, R0
LDR R0, =OSPrioCur ; OSPrioCur = OSPrioHighRdy; LDR R1, =OSPrioHighRdy LDRB R2, [R1] STRB R2, [R0]
LDR R0, =OSTCBCur ; OSTCBCur = OSTCBHighRdy; LDR R1, =OSTCBHighRdy LDR R2, [R1] STR R2, [R0]
LDR R0, [R2] ; R0 is new process SP; SP = OSTCBHighRdy->OSTCBStkPtr;
LDM R0!, {R4-R7} ; Restore R4-R7 from new process stack
MSR PSP, R0 ; Load PSP with new process SP
MOV R0, R14 MOVS R1, #0x04 ; Immediate move to register ORRS R0, R1 ; Ensure exception return uses process stack MOV R14, R0 CPSIE I BX LR ; Exception return will restore remaining context; ALIGN ; Ensures that ARM instructions start on four-byte boundary
END