Quality RTOS & Embedded Software

 Real time embedded FreeRTOS RSS feed 
Quick Start Supported MCUs PDF Books Trace Tools Ecosystem


Stack sizes in my Startup.s file

Posted by Thomas Johansen on July 1, 2009

Im using FreeRTOS on a LPC2478 ARM7 microcontroller.
I have a question recarding stack sizes in my startup file.

Im using KEIL uVision as compiler and mem scheme 2 as memory manager.

As I understand, then the heap (in heap_2.c) is where createTask takes a chunk out every time a task is created. When a task is created the tasks stack size must be supplied. So the combined stack sizes of all the tasks must be smaller then the heap size, incl some task info (defined with configTOTAL_HEAP_SIZE). ???

The task runs in user mode (ARM7 CPU mode). In the startup.s file I can allocate stacks for each processor mode. So, if I'm right, then the user stack size in my startup.s file, must be at least my heap size? Or must it just be minimum my greates task stack size??


RE: Stack sizes in my Startup.s file

Posted by Dave on July 1, 2009
You need to allocated space for the Supervisor stack and IRQ stack only. FIQ stack needs to be allocated only if you use FIQ interrupts. Tasks stacks as you rightly say come from the heap so you don't need to allocate any user mode stacks.

There are lots of examples in the download for you to copy.

[ Back to the top ]    [ About FreeRTOS ]    [ Privacy ]    [ Sitemap ]    [ ]

Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.

Latest News

Version 10.1.0 of the FreeRTOS kernel is available for immediate download. MIT licensed.

View a recording of the "OTA Update Security and Reliability" webinar, presented by TI and AWS.


FreeRTOS and other embedded software careers at AWS.

FreeRTOS Partners

ARM Connected RTOS partner for all ARM microcontroller cores

Espressif ESP32

IAR Partner

Microchip Premier RTOS Partner

RTOS partner of NXP for all NXP ARM microcontrollers


STMicro RTOS partner supporting ARM7, ARM Cortex-M3, ARM Cortex-M4 and ARM Cortex-M0

Texas Instruments MCU Developer Network RTOS partner for ARM and MSP430 microcontrollers

OpenRTOS and SafeRTOS

Xilinx Microblaze and Zynq partner