Real-time operating system
Operating system
FreeRTOS
|
Developer
| Amazon Web Services
|
---|
Written in
| C
|
---|
OS family
| Real-time operating systems
|
---|
Working state
| Current
|
---|
Source model
| Open source
|
---|
Initial release
| 2003
; 21 years ago
(
2003
)
|
---|
Latest release
| 10.6.1
[1]
/ July 13, 2023
; 11 months ago
(
2023-07-13
)
|
---|
Repository
| |
---|
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
,
Renesas
H8/S
,
SuperH
, RX,
x86
,
8052
,
Coldfire
,
V850
, 78K0R, Fujitsu series MB91460, MB96340,
Nios II
, TMS570, RM4x,
Espressif ESP32
,
RISC-V
(e.g.
SHAKTI
)
|
---|
Kernel
type
| Real-Time
Microkernel
|
---|
License
| MIT
[2]
|
---|
Official website
| www
.freertos
.org
|
---|
FreeRTOS
is a
real-time operating system
kernel
[3]
[4]
[5]
for
embedded devices
that has been ported to 35
microcontroller
platforms. It is distributed under the
MIT License
.
History
[
edit
]
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 to
Amazon Web Services
(AWS). Barry continues to work on FreeRTOS as part of an AWS team.
[6]
Implementation
[
edit
]
FreeRTOS is designed to be small and simple. It is mostly written in the
C programming language
to make it easy to port and maintain. It also comprises a few
assembly language
functions where needed, mostly in architecture-specific scheduler routines.
Process management
[
edit
]
FreeRTOS provides methods for multiple
threads
or
tasks
,
mutexes
,
semaphores
and
software timers
. A
tickless
mode 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 of
memory management
(allocation):
- allocate only;
- allocate and free with a very simple, fast, algorithm;
- a more complex but fast allocate and free algorithm with
memory 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 in
operating systems
like
Linux
and
Microsoft Windows
, such as
device 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-like
input/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 a
round-robin scheduling
scheme. The usual interval is 1 to 10 milliseconds (
1
⁄
1000
to
1
⁄
100
of 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
[
edit
]
- 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.
- Coroutine
support (coroutines in FreeRTOS are simple and lightweight
tasks
with limited use of the
call stack
)
- Trace support through generic trace macros. Tools such as Tracealyzer, a commercial tool by FreeRTOS partner Percepio, can thereby record and visualize the
runtime
behavior of FreeRTOS-based systems for debugging and verification. This includes task scheduling and kernel calls for semaphore and queue operations.
Supported architectures
[
edit
]
Derivations
[
edit
]
Amazon FreeRTOS
[
edit
]
Amazon
provides a now deprecated extension of FreeRTOS, this is FreeRTOS with libraries for
Internet of things
(IoT) support, specifically for
Amazon Web Services
. Since version 10.0.0 in 2017, Amazon has taken stewardship of the FreeRTOS code, including any updates to the original kernel.
[8]
[9]
[10]
SAFERTOS
[
edit
]
SAFERTOS was developed as a complementary version of FreeRTOS, with common functions, but designed for safety-critical implementation. FreeRTOS was subject to
hazard and operability study
(HAZOP), and weaknesses were identified and resolved. The result was put through a full
IEC 61508
SIL 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 developer
[3]
of the FreeRTOS project.
[11]
Both SAFERTOS and FreeRTOS share the same scheduling algorithm, have similar application programming interfaces (
APIs
), and are otherwise very similar,
[12]
but they were developed with differing objectives.
[13]
SAFERTOS was developed solely in the
C language
to meet requirements for certification to IEC61508.
[14]
SAFERTOS can reside solely in the on-chip
read-only memory
(ROM) of a microcontroller for standards compliance.
[15]
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.
[16]
SAFERTOS is included in the ROM of some Stellaris Microcontrollers
[17]
from 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
[
edit
]
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.
[18]
[19]
See also
[
edit
]
References
[
edit
]
External links
[
edit
]
Wikimedia Commons has media related to
FreeRTOS
.