Quality RTOS & Embedded Software

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


Undefined Priority

Posted by Alexander Zurkan on July 26, 2008
Hi there,

I examined FreeRTOS in depth a little bit the last few days and came across some questions I'd like to discuss with you. I will start a new thread for each question, because they belong to different categories. I also need some webspace for uploading images to explain my other questions, it will take while before I will post them. So lets beginn with the first simple one:

In the FreeRTOS configuration I specified 8 priorities as: #define configMAX_PRIORITIES( ( unsigned portBASE_TYPE ) 8 ).
Then I created a task with a priority of 41. Well, compiling the sources and running it (on ATmega128) shows that everything is working well. Even the task with 41 priority. Examination with a logic analyzer showed, that this task executes as a task with mid Priority such as 3 or 4.

Can anyone explain that behaviour?

Best Regards,

RE: Undefined Priority

Posted by woops_ on July 26, 2008
If you study the source code then you see the code

if( uxPriority >= configMAX_PRIORITIES )
uxPriority = configMAX_PRIORITIES - 1;
so it is limited.

RE: Undefined Priority

Posted by Alexander Zurkan on July 26, 2008
Thanks for the answer. I think I missed that line in the sources.

Best Regards,

[ 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