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王偉一 江哲維 洪心為
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• PART1
• Introduction
• PART2
• Architecture
• PART3
• Application
• Future View
• Conclusion
王偉一，江哲維，洪心為

PART
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9961257 王偉一
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• A R eal T ime O perating S ystem
• Written by Richard Barry & FreeRTOS Team
• Owned by Real Time Engineers Ltd but free to use
• Huge number of users all over the world
• 6000 Download per month
• Simple but very powerful
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王偉一 ，江哲維，洪心為

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• A type of an operating system
• It’s all about scheduler :
• multi user operating system(UNIX) － fair amount of the processing time
• desk top operating system(Windows) － remain responsive to its user
• ……
• RTOS scheduler focuses on predictable execution pattern
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• Abstract out timing information
• Maintainability/Extensibility
• Modularity
• Cleaner interfaces
• Easier testing (in some cases)
• Code reuse
• Improved efficiency?
• Idle time
…...
……
王偉一 ，江哲維，洪心為

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王偉一 ，江哲維，洪心為

 Modified GPL
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FreeRTOS v1.0.1
FreeRTOS v2.0.0
FreeRTOS v3.0.0
FreeRTOS v4.0.0
FreeRTOS v5.0.0
+Scalability
+New Task API
+API Changes
+Directory
Names
Changed
+Changes in
Kernel
+Co-routines +API Changes
王偉一 ，江哲維，洪心為

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FreeRTOS v7.6.0
+ Tick Suppression
+ Queue sets
+ Port optimized task selection http://www.freertos.org/History.txt
王偉一 ，江哲維，洪心為

PART
II
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• Tasks (50%)
• task.c
and task.h
do all the heavy lifting for creating, scheduling, and maintaining tasks.
• Communication (40%)
• queue.c
and queue.h
handle FreeRTOS communication.
Tasks and interrupts use queues to send data to each other and to signal the use of critical resources using semaphores and mutexes.
• Hardware Interfacing (6%)
王偉一，江哲維， 洪心為

(1/3)
• Running
• Ready
• Blocked
• Suspended
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(2/3)
• Each task is assigned a priority from 0 to
( configMAX_PRIORITIES - 1 ). Low priority numbers denote low priority tasks. The idle task has priority zero (tskIDLE_PRIORITY).
• The task placed into the Running state is always be the highest priority task that is able to run.
• Ready state tasks of equal priority share the available processing time using a time sliced round robin scheduling scheme.
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(3/3)
• Created automatically when the RTOS scheduler is started to ensure there is always at least one task that is able to run.
• Responsible for freeing memory allocated by the
RTOS to tasks that have since been deleted.
• An idle task hook is a function that is called during each cycle of the idle task.
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Communication & Synchronization
• Queues
• Binary Semaphores
• Counting Semaphores
• Mutexes
• Recursive Mutexes
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• Hardware Independent
• The same code runs whether FreeRTOS is running on the humble 8051 or the newest, shiniest ARM core.
• FreeRTOS software layers
王偉一，江哲維， 洪心為

PART
III
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• Because of the basic kernel of FreeRTOS, it’s more flexible for users to attach other expanded modules on OS to get more applications.
• New cloud managed service, file system API, TCP/IP, safety certified kernel…
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• FreeRTOS+Nabto is a small piece of C code.
• Each Internet of Things (IoT) device has a unique URL over the Internet, and the technology allows secure, authenticated and extremely low bandwidth P2P connections.
• accessible over a local network in the absence of Internet connectivity.
• combined with FreeRTOS's special low power features, makes FreeRTOS a natural choice for implementing the Internet of Things.
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• A resolvable URL for each device
• Remote access over the Internet from computer, tablet or smart phone
• No firewall hassles
• No embedded file system, TCP/IP stack necessary
• Low bandwidth for enhanced performance
• Increased privacy and security
• Reduced hardware and software cost
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• An Free Real-Time OS with essential kernel of low power(Tick-less kernel) & high efficiency.
• Support many architecture.
Ex. ARM, Altera, Xilinx, IBM, Intel, Cortus…
• Co-routine – multitasking by coding
• Open source, implantable, flexible and easy learning
王偉一， 江哲維 ，洪心為

• The Architecture of Open Source Applications (Volume 2): FreeRTOS http://www.aosabook.org/en/freertos.html
• FreeRTOS official Website http://www.freertos.org/
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