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DOCUMENTATION

FreeRTOS quick start

RTOS fundamentals

FreeRTOS kernel quick start guide

Build your first project

FreeRTOS libraries and 3rd party tools

FreeRTOS plus AWS solutions

Join the FreeRTOS community

Kernel

FreeRTOS kernel

Quality management

DownloadFreeRTOS

FreeRTOS Developer docs

Tasks and co-routines

Task priorities

Task scheduling

Implementing a task

Co-routine overview

Co-routine states

Implementing a co-routine

Co-routine priorities

Scheduling co-routines

Limitations and restrictions

Co-routine example

Standard demo examples

Thread local storage pointers

Binary semaphores

Counting semaphores

Recursive mutexes

Task notifications

As binary semaphore

As counting semaphore

Inter Task Communication

RTOS stream and message buffers

Stream buffer example

Message buffer example

Software timers

Timer service daemon task

Timer daemon configuration

One shot vs auto load

Resetting a timer

Lower power support

Run time statistics

RTOS trace feature

Memory management

Stack usage and stack overflow checking

Static vs Dynamic memory allocation

Static allocation demo

Blocking on multiple RTOS objects

Deferred interrupt handling

Symmetric multiprocessing introduction

Supported devices

FreeRTOS porting guide

Official vs 3rd party

Supported demos

Emulation and simulation

Modifying demos

xTaskCreateStatic

vTaskDelayUntil

xTaskDelayUntil

uxTaskPriorityGet

vTaskPrioritySet

xTaskResumeFromISR

xTaskAbortDelay

uxTaskPriorityGetFromISR

uxTaskBasePriorityGet

uxTaskBasePriorityGetFromISR

uxTaskGetSystemState

xTaskGetApplicationTaskTag

uxTaskGetStackHighWaterMark

xTaskCallApplicationTaskHook

vTaskSetApplicationTag

vTaskSetThreadLocalStoragePointer

pvTaskGetThreadLocalStoragePointer

vTaskSetTimeOutState

xTaskCheckForTimeOut

eTaskConfirmSleepModeStatus

taskENTER CRITICAL taskEXIT CRITICAL

taskENTER CRITICAL FROM ISR taskEXIT CRITICAL FROM ISR

vTaskStartScheduler

vTaskEndScheduler

vTaskSuspendAll

xTaskCatchUpTicks

RTOS task notifications

xTaskNotifyGive

vTaskNotifyGiveFromISR

ulTaskNotifyTake

xTaskNotifyAndQuery

xTaskNotifyAndQueryFromISR

xTaskNotifyFromISR

xTaskNotifyWait

xTaskNotifyStateClear

ulTasknotifyValueClear

QueueManagement

xQueueCreateStatic

xQueueSendFromISR

xQueueSendToBack

xQueueSendToBackFromISR

xQueueSendToFront

xQueueSendToFrontFromISR

xQueueReceiveFromISR

xQueueOverwrite

xQueueOverwriteFromISR

xQueuePeekFromISR

vQueueAddToRegistry

vQueueUnregisterQueue

xQueueGetStaticBuffers

RTOS queue sets

xQueueCreateSet

xQueueCreateSetStatic

xQueueRemoveFromSet

xQueueSelectFromSet

xQueueSelectFromSetFromISR

RTOS stream buffer API

xStreamBufferCreate

xStreamBufferCreateStatic

xStreamBufferSend

xStreamBufferSendFromISR

xStreamBufferReceive

xStreamBufferReceiveFromISR

vStreamBufferDelete

xStreamBufferBytesAvailable

xStreamBufferSpacesAvailable

xStreamBufferSetTriggerLevel

xStreamBufferReset

xStreamBufferIsEmpty

xStreamBufferIsFull

xStreamBufferResetFromISR

xStreamBufferGetStaticBuffers

uxStreamBufferGetStreamBufferNotificationIndex

vStreamBufferSetStreamBufferNotificationIndex

xStreamBatchingBufferCreate

xStreamBatchingBufferCreateStatic

RTOS message buffer API

xMessageBufferCreate

xMessageBufferCreateStatic

xMessageBufferSend

xMessageBufferSendFromISR

xMessageBufferReceive

xMessageBufferReceiveFromISR

vMessageBufferDelete

xMessageBufferSpacesAvailable

xMessageBufferReset

xMessageBufferIsEmpty

xMessageBufferIsFull

xMessageBufferResetFromISR

xMessageBufferGetStaticBuffers

xSemaphoreCreateBinary

xSemaphoreCreateBinaryStatic

vSemaphoreCreateBinary

xSemaphoreCreateCounting

xSemaphoreCreateCountingStatic

xSemaphoreCreateMutex

xSemaphoreCreateMutexStatic

xSemaphoreCreateRecursiveMutex

xSemaphoreCreateRecursiveMutexStatic

xSemaphoreGetMutexHolder

uxSemaphoreGetCount

xSemaphoreTakeFromISR

xSemaphoreTakeRecursive

xSemaphoreGiveRecursive

xSemaphoreGiveFromISR

vSemaphoreDelete

FreeRTOS Software Timer API Functions

xTimerIsTimerActive

xTimerChangePeriod

xTimerStartFromISR

xTimerStopFromISR

xTimerChangePeriodFromISR

xTimerResetFromISR

pvTimerGetTimerID

vTimerSetReloadMode

vTimerSetTimerID

xTimerPendFunctionCall

xTimerPendFunctionCallFromISR

xTimerGetPeriod

xTimerGetExpiryTime

xTimerCreateStatic

xTimerGetReloadMode

xEventGroupCreate

xEventGroupCreateStatic

vEventGroupDelete

xEventGroupWaitBits

xEventGroupSetBits

xEventGroupSetBitsFromISR

xEventGroupClearBits

xEventGroupClearBitsFromISR

xEventGroupGetBits

xEventGroupGetBitsFromISR

xEventGroupSync

xEventGroupGetStaticBuffer

FreeRTOS MPU specific

xTaskCreateRestricted

xTaskCreateRestrictedStatic

vTaskAllocateMPURegions

portSWITCH TO USER MODE

xCoRoutineCreate

crQUEUE RECEIVE

crQUEUE SEND FROM ISR

crQUEUE RECEIVE FROM ISR

vCoRoutineSchedule

RTOS implementation

Building blocks

C development tools

GCC signal attribute

GCC naked attributes

FreeRTOS tick code

The AVR context

Saving the RTOS task context

Restoring the context

Tick Resolution

Putting it all together

Source code organization

FreeRTOS Coding Standard and Style Guide

Libraries

FreeRTOS Plus TCP

Networking basics

Ethernet addressing

Internet protocol

Client and servers

Static IP address

Name resolution

Multiple interfaces

IPv6 functionality

IPv6 multi functions

TCP networking tutorial

Source code organization

Including in a project

Creating TCP sockets

Sending TCP data

Receiving TCP data

Closing a TCP socket

Creating a UDP socket

Sending UDP data

Sending UDP data zero copy

Receiving UDP data

Receiving UDP data zero copy

Initialising the TCP/IP Stack

Receiving Data Using a TCP Socket (zero copy interface)

Sending Data Using a TCP Socket (zero copy interface)

Buffer management

Configuration examples

FreeRTOS plus TCP APIs

FreeRTOS_socket

FreeRTOS_connect

FreeRTOS_listen

FreeRTOS_accept

FreeRTOS_sendto

FreeRTOS_recvfrom

FreeRTOS_setsockopt

FreeRTOS_shutdown

FreeRTOS_closesocket

FreeRTOS_select

FreeRTOS_CreateSocketSet

FreeRTOS_FD_SET

FreeRTOS_FD_CLR

FreeRTOS_FD_ISSET

FreeRTOS_gethostbyname

FreeRTOS_inet_ntoa

FreeRTOS_inet_addr_quick

FreeRTOS_inet_addr

htons ntohs htonl ntohl

FreeRTOS_outstanding

FreeRTOS_recvcount

FreeRTOS_issocketconnected

FreeRTOS_GetLocalAddress

FreeRTOS_GetRemoteAddress

FreeRTOS_maywrite

FreeRTOS_IPInit

FreeRTOS_IPInit_Multi

FreeRTOS_GetAddressConfiguration

FreeRTOS_GetUDPPayloadBuffer

FreeRTOS_ReleaseUDPPayloadBuffer

FreeRTOS_SendPingRequest

FreeRTOS_GetMACAddress

FreeRTOS_GetIPAddress

FreeRTOS_GetIPType

FreeRTOS_SetGatewayAddress

FreeRTOS_GetDNSServerAddress

FreeRTOS_GetNetmask

FreeRTOS_OutputARPRequest

FreeRTOS_IsNetworkUp

FreeRTOS_AllEndPointsUp

FreeRTOS_IsEndPointUp

FreeRTOS_SetAddressConfiguration

FreeRTOS_SetEndPointConfiguration

FreeRTOS_GetGatewayAddress

FreeRTOS_SetIPAddress

FreeRTOS_SetNetmask

FreeRTOS_SignalSocket

FreeRTOS_FillEndPoint

FreeRTOS_FillEndPoint_IPv6

eApplicationProcessCustomFrameHook

pcApplicationHostnameHook

vApplicationIPNetworkEventHook

vApplicationIPNetworkEventHook_Multi

vApplicationPingReplyHook

xApplicationDHCPHook

xApplicationDNSQueryHook

ulApplicationGetNextSequenceNumber

xApplicationGetRandomNumber

xApplicationDHCPHook_Multi

xApplicationDNSQueryHook_Multi

FreeRTOS_getaddrinfo

FreeRTOS_getaddrinfo_a

FreeRTOS_rx_size

FreeRTOS_gethostbyname_a

FreeRTOS TCP Porting

Embedded Compiler Porting

Embedded Ethernet Porting

Network interface functions

FreeRTOS_AddNetworkInterface

pxGetNetworkBufferWithDescriptor

vReleaseNetworkBufferAndDescriptor

pucGetNetworkBuffer

vReleaseNetworkBuffer

eConsiderFrameForProcessing

xSendEventStructToIPTask

FreeRTOS_FirstEndpoint

FreeRTOS_MatchingEndpoint

FreeRTOS_NextEndpoint

TCP FAT demo projects

Basic stdio API test

Creating a disk

File system CLI

HTTP web server

FreeRTOS plus TCP licensing

FreeRTOS plus CLI

Implementing a command

Command parameters

Registering a command

Calling the interpreter

A FreeRTOS plus CLI task

Buffer management

FreeRTOS Plus IO

FreeRTOS IO API Functions

Polled Transfer Mode

Zero Copy Transfer Mode

Circular Buffer Transfer Mode

Character Queue Transfer Mode

NXP LPC1769 Demo Description

FreeRTOS Plus IO License

FreeRTOS Plus IO Configuration

backoff algorithm

Percepio View for FreeRTOS

FreeRTOS-Plus-Trace and FreeRTOS-Plus-CLI Demo

MQTT terminology

coreMQTT demo LTS

Mutual authentication

Keep Alive demo

coreMQTT agent demo

coreMQTT agent API reference

coreHTTP terminology

Mutual authentication

Basic S3 upload demo

Basic S3 download demo

Multithreaded demo

coreSNTP terminology

Setting up an NTP server

coreSNTP API reference

Transport interface

TLS introduction

TLS terminology

X509 certificates

coreJSON terminology

PKCS11 functions

Mutual authentication demo

Management and RNG demo

Mechanisms and Digests demo

Sign and verify demo

Cellular interface

Cellular interface demo

Cellular interface API reference

coreMQTT File Streams

coreMQTT agent API reference

coreSNTP API reference

Cellular interface API reference

OTA terminology

AWS IoT device shadow

Design for named shadow support

Shadow terminology

Device shadow demo

AWS IoT Device Shadow Library

Jobs terminology

AWS IoT Jobs Client Library

AWS IoT device defender

Device defender demo

Demo with MQTT agent

AWS IoT Device Defender Client Library

AWS IoT fleet provisioning

Fleet provisioning terminology

Fleet provisioning demo

AWS IoT Fleet Provisioning Library

AWS signature version 4

SigV4 terminology

HTTP S3 download demo

AWS SigV4 Library

AWS reference integrations

AWS IoT Device Shadow Library

AWS IoT Jobs Client Library

AWS IoT Device Defender Client Library

AWS IoT Fleet Provisioning Library

AWS SigV4 Library

LoRaWAN library

LoRaWAN API reference

FreeRTOS+POSIX Demo

FreeRTOS plus FAT

Source code organization

Standard API errno values

Standard File System API

FreeRTOS MCUBoot

Task pool library

Over the air updates

OTA (Using Simple OTA Orchestrator)

OTA (Using OTA Agent Orchestrator)

Featured integrations

Espressif ESP32 C3

ARM corstone 3xx

NXP i.MX RT1060

ST Microelectronics STM32U5

STM32 Expresslink integration

Roadmap and release note

Release history

FreeRTOS V10.3.0

FreeRTOS V10.4.x

FreeRTOS V10.4.5

FreeRTOS V10.4.6

FreeRTOS V10.5.0

LibrariesFreeRTOS plus IO

Updated Jul 2025

FreeRTOS-Plus-IO License

From FreeRTOS V10.0.0 FreeRTOS-Plus-IO is provided under the same MIT license as the FreeRTOS kernel.

Related links

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