FreeRTOS Real Time Kernel

Hallo

I may have some stack/heap problem!?? But im not sure.

Im using the latest FreeRTOS on my LPC2478. I have 5 tasks and they are working fine.

But know I whant to add some graphics task to my project. So I create a new task, which draw some graphics in my framebuffer in a given interval. But when the task runs, then I get an Abort exception. If I check the excpetion cause and extract the assembly where it happens, then its in the context switch rutine.

What I can see in the debugger before the exception(Keil uVision), a structure passed to a graphics function is suddenly out of scope... So when the function returns I get the data abort exception.

My guess is that maybee my stack is to small? The graphics function uses many bytes of RAM. Could that be a the cause?
If I call the graphics function from the main, before the scheduler is started, then there is no problem, but when called from the task I get an exception.

Does tasks run in supervisor mode? or user mode?

This is my stack and heap setup:

UND_Stack_Size EQU 0x00000008
SVC_Stack_Size EQU 0x00000400
ABT_Stack_Size EQU 0x00000008
FIQ_Stack_Size EQU 0x00000008
IRQ_Stack_Size EQU 0x00000400
USR_Stack_Size EQU 0x00000008

ISR_Stack_Size EQU (UND_Stack_Size + SVC_Stack_Size + ABT_Stack_Size + \
FIQ_Stack_Size + IRQ_Stack_Size)

AREA STACK, NOINIT, READWRITE, ALIGN=3

Stack_Mem SPACE USR_Stack_Size
__initial_sp SPACE ISR_Stack_Size

Stack_Top

;// <h> Heap Configuration
;// <o> Heap Size (in Bytes) <0x0-0xFFFFFFFF>
;// </h>

Heap_Size EQU 0x00000000

AREA HEAP, NOINIT, READWRITE, ALIGN=3
__heap_base
Heap_Mem SPACE Heap_Size
__heap_limit


If I look in my Startup.s file, I do not set the user mode stack pointer? Schouldnet I do that?

; Setup Stack for each mode ----------------------------------------------------

LDR R0, =Stack_Top

; Enter Undefined Instruction Mode and set its Stack Pointer
MSR CPSR_c, #Mode_UND:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #UND_Stack_Size

; Enter Abort Mode and set its Stack Pointer
MSR CPSR_c, #Mode_ABT:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #ABT_Stack_Size

; Enter FIQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_FIQ:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #FIQ_Stack_Size

; Enter IRQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_IRQ:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #IRQ_Stack_Size

; Enter Supervisor Mode and set its Stack Pointer
MSR CPSR_c, #Mode_SVC:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #SVC_Stack_Size

EXPORT __initial_sp
; Enter User Mode and set its Stack Pointer
; MSR CPSR_c, #Mode_USR
; IF :DEF:__MICROLIB

; EXPORT __initial_sp

; ELSE

; MOV SP, R0
; SUB SL, SP, #USR_Stack_Size

; ENDIF

; Enter the C code -------------------------------------------------------------

IMPORT __main
LDR R0, =__main
BX R0


IF :DEF:__MICROLIB

EXPORT __heap_base
EXPORT __heap_limit

ELSE
; User Initial Stack & Heap
AREA |.text|, CODE, READONLY

IMPORT __use_two_region_memory
EXPORT __user_initial_stackheap
__user_initial_stackheap

LDR R0, = Heap_Mem
LDR R1, =(Stack_Mem + USR_Stack_Size)
LDR R2, = (Heap_Mem + Heap_Size)
LDR R3, = Stack_Mem
BX LR
ENDIF


END


/Thomas