FreeRTOS

FreeRTOS

Developer	Amazon Web Services
Written in	C
OS family	Real-time operating systems
Working state	Current
Source model	Open source
Initial release	2003(2003)
Latest release	10.6.1/ July 13, 2023(2023-07-13)
Repository	github/FreeRTOS/FreeRTOS
Marketing target	Embedded systems
Available in	English
Platforms	ARM(ARM7, ARM9,Cortex-M3,-M4,-M7,-A,-R4),Atmel AVR,AVR32,HCS12,MicroBlaze,Cortus (APS1, APS3, APS3R, APS5, FPF3, FPS6, FPS8),MSP430,PIC,RenesasH8/S,SuperH,RX,x86,8052,Coldfire,V850,78K0R, Fujitsu series MB91460, MB96340,Nios II,TMS570, RM4x,Espressif ESP32,RISC-V(e.g.SHAKTI)
Kerneltype	Real-TimeMicrokernel
License	MIT
Official website	www.freertos.org

FreeRTOSis areal-time operating systemkernelforembedded devicesthat has been ported to 35microcontrollerplatforms. It is distributed under theMIT License.

History

The FreeRTOS kernel was originally developed by Richard Barry around 2003, and was later developed and maintained by Barry's company, Real Time Engineers Ltd. In 2017, the firm passed stewardship of the FreeRTOS project toAmazon Web Services(AWS). Barry continues to work on FreeRTOS as part of an AWS team.

Implementation

FreeRTOS is designed to be small and simple. It is mostly written in theC programming languageto make it easy to port and maintain. It also comprises a fewassembly languagefunctions where needed, mostly in architecture-specific scheduler routines.

Process management

FreeRTOS provides methods for multiplethreadsortasks,mutexes,semaphoresandsoftware timers.Aticklessmode is provided for low power applications. Thread priorities are supported. FreeRTOS applications can be statically allocated, but objects can also be dynamically allocated with five schemes ofmemory management(allocation):

• allocate only;
• allocate and free with a very simple, fast, algorithm;
• a more complex but fast allocate and free algorithm withmemory coalescence;
• an alternative to the more complex scheme that includes memory coalescence that allows a heap to be broken across multiple memory areas.
• and C library allocate and free with some mutual exclusion protection.

RTOSes typically do not have the more advanced features that are found inoperating systemslikeLinuxandMicrosoft Windows,such asdevice drivers,advanced memory management, and user accounts. The emphasis is on compactness and speed of execution. FreeRTOS can be thought of as a thread library rather than an operating system, although command line interface and POSIX-likeinput/output(I/O) abstraction are available.

FreeRTOS implements multiple threads by having the host program call a thread tick method at regular short intervals. The thread tick method switches tasks depending on priority and around-robin schedulingscheme. The usual interval is 1 to 10 milliseconds (1⁄1000to1⁄100of a second) via an interrupt from a hardware timer, but this interval is often changed to suit a given application.

The software distribution contains prepared configurations and demonstrations for every port and compiler, allowing rapid application design. The project website provides documentation and RTOS tutorials, and details of the RTOS design.

Key features

• Book and reference manuals.
• Small memory size, low overhead, and fast execution.
• Tick-less option for low power applications.
• Intended for both hobbyists and professional developers working on commercial products.
• Scheduler can be configured for both preemptive or cooperative multitasking.
• Coroutinesupport (coroutines in FreeRTOS are simple and lightweighttaskswith limited use of thecall stack)
• Trace support through generic trace macros. Tools such as Tracealyzer, a commercial tool by FreeRTOS partner Percepio, can thereby record and visualize theruntimebehavior of FreeRTOS-based systems for debugging and verification. This includes task scheduling and kernel calls for semaphore and queue operations.

Supported architectures

• AlteraNios II
• ARM architecture
  • ARM7
  • ARM9
  • ARM Cortex-M
  • ARM Cortex-A
• Atmel
  • Atmel AVR
  • AVR32
  • SAM3, SAM4
  • SAM7, SAM9
  • SAMD20, SAML21
• Ceva
  • Ceva-BXx
  • SensPro
  • Ceva-XC16
  • Ceva-XM6
  • Ceva-Xx
  • Ceva-XM4
• Cortus
  • APS1
  • APS3
  • APS3R
  • APS5
  • FPS6
  • FPS8
• Cypress
  • PSoC
• Energy Micro
  • EFM32
• eSi-RISC
  • eSi-16x0
  • eSi-32x0
• DSP Group
  • DBMD7
• Espressif
  • ESP8266
  • ESP32
• Fujitsu
  • FM3
  • MB91460
  • MB96340
• Freescale
  • ColdfireV1, V2
  • HCS12
  • Kinetis
• IBM
  • PPC404,PPC405
• Infineon
  • TriCore
  • Infineon XMC4000
• Intel
  • x86
  • 8052
• Microchip Technology
  • PIC18, PIC24, dsPIC
  • PIC32
• Microsemi
  • SmartFusion
• Multiclet
  • P1
• NXP
  • LPC1000
  • LPC2000
  • LPC4300
• Renesas
  • 78K0R
  • RL78
  • H8/S
  • RX600
  • RX200
  • SuperH
  • V850
• RISC-V
  • RV32I
  • RV64I
  • PULP RI5CY
• Silicon Labs
  • Gecko (ARM Cortex)
• STMicroelectronics
  • STM32
  • STR7
• Texas Instruments
  • C2000 series (TMS320F28x)
  • MSP430
  • Stellaris
  • Hercules(TMS570LS04 & RM42)
• Xilinx
  • MicroBlaze
  • Zynq-7000

Derivations

Amazon FreeRTOS

Amazonprovides a now deprecated extension of FreeRTOS, this is FreeRTOS with libraries forInternet of things(IoT) support, specifically forAmazon Web Services.Since version 10.0.0 in 2017, Amazon has taken stewardship of the FreeRTOS code, including any updates to the original kernel.

SAFERTOS

SAFERTOS was developed as a complementary version of FreeRTOS, with common functions, but designed for safety-critical implementation. FreeRTOS was subject tohazard and operability study(HAZOP), and weaknesses were identified and resolved. The result was put through a fullIEC 61508SIL 3 development lifecycle, the highest level for a software-only component.

SAFERTOS was developed by Wittenstein High Integrity Systems, in partnership with Real Time Engineers Ltd, primary developerof the FreeRTOS project.Both SAFERTOS and FreeRTOS share the same scheduling algorithm, have similar application programming interfaces (APIs), and are otherwise very similar,but they were developed with differing objectives.SAFERTOS was developed solely in theC languageto meet requirements for certification to IEC61508.

SAFERTOS can reside solely in the on-chipread-only memory(ROM) of a microcontroller for standards compliance.When implemented in hardware memory, SAFERTOS code can only be used in its original, certified configuration. This means certifying a system needs no retesting of the kernel portion of a design.SAFERTOS is included in the ROM of some Stellaris Microcontrollersfrom Texas Instruments. SAFERTOS source code does not need to be separately purchased. In this usage scenario, a C header file is used to map SAFERTOS API functions to their location in read-only memory.

OPENRTOS

OPENRTOS is a commercially licensed version of Amazon FreeRTOS, sold by Wittenstein High Integrity Systems. This product provides support and allows companies to use the Amazon FreeRTOS kernel and libraries without the a:FreeRTOS MIT license.

See also

• Embedded operating system

External links

• Official website