Quality RTOS & Embedded Software

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


RTOS Task Notifications
Used As Light Weight Mailbox

Related pages:


RTOS task notifications can be used to send data to a task, but in a much more restricted way than can be achieved with an RTOS queue because:

  1. Only 32-bit values can be sent
  2. The value is saved as the receiving task's notification value, and there can only be one notification value at any one time
Hence the phrase 'lightweight mailbox' is used in preference to 'lightweight queue'. The task's notification value is the mailbox value.

Data is sent to a task using the xTaskNotify() and xTaskNotifyFromISR() API functions with their eAction parameter set to either eSetValueWithOverwrite or eSetValueWithoutOverwrite. If eAction is set to eSetValueWithOverwrite then the receiving task's notification value is updated even if the receiving task already had a notification pending. If eAction is set to eSetValueWithoutOverwrite then the receiving task's notification value is only updated if the receiving task did not already have a notification pending - as to update the notification value would overwrite the previous value before the receiving task had processed it.

A task can read its own notification value using xTaskNotifyWait().

See the documentation for the relevant API functions for examples.




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


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

Latest News

NXP tweet showing LPC5500 (ARMv8-M Cortex-M33) running FreeRTOS.

Meet Richard Barry and learn about running FreeRTOS on RISC-V at FOSDEM 2019

Version 10.1.1 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.


Careers

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

Renesas

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