Quality RTOS & Embedded Software

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


Stack size using Heap 2

Posted by Nobody/Anonymous on September 6, 2005
A friend myself recently completed porting freeRTOS onto a AVR Mega16, using timer 0 as the main clock timer as we wanted to user timer 1 for PWM's. This particular part only has 1k of ram, so we are concerned with the number of tasks which may run currently and also stack size.

Question is this:

We would like to use the Heap_2 memory management strategy and delete and create tasks on the fly, so our main concern is fragmentation.

If we use the minimum stack size (83 bytes), will this work?

Does the stack size vary dynamically?

What are the concerns?


RE: Stack size using Heap 2

Posted by Richard on September 8, 2005
Sorry for the delay in responding – but I have been out of the office for the last 4 days.

Have you seen the following page?

These figures were taken on an AVR using GCC.

1K is really a very small amount of RAM to have available. What you can do with it will depend on what else is using RAM in your system. Take a look at the application design pages of the FreeRTOS site for ideas on minimising RAM usage: http://www.freertos.org/tutorial/

I would suggest adding a few lines at the bottom of the pvPortMalloc() in heap_2.c to test whether NULL is returned (indicating that there is insufficient memory available). You can then set a break point on the line (if NULL is returned) to immediately know if you are running out of memory.


RE: Stack size using Heap 2

Posted by Nobody/Anonymous on September 9, 2005
Thanks Richard,

that's a a good suggestion.


[ 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