Date post: | 06-Jan-2017 |
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Introduction to RTOS
Yong Heui Cho @ Mokwon University
Most of slides are referred to and all credits should go to:[1] Swetanka Kumar Mishra & Kirti Chawla, RTOS Design & Implementation, slideshare, 2014.
2
Smart Device Structure
8. Introduction to IoT
9. Smart Device RF & Anten-nas10. Introduction to RTOS
11. Introduction to Bluetooth
3
RTOS• Real-Time Operating System• A variant of OS that operates in
constrained environment in which computer memory and processing power is limited– Moreover they often need to provide
their services in definite amount of time.• Hard, Soft & Firm RTOS• Example RTOS: VxWorks, pSOS,
Nucleus, RTLinux
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
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Types of RTOS
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Structure of RTOS
Custom-Hardware
RTOS-kernel
Applications
BSP
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
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Component of RTOS• The most important component
of RTOS is its kernel.– Monolithic & Microkernel
• BSP or Board Support Package makes an RTOS target-specific.– It’s a processor specific code onto
(processor) which we like to have our RTOS running.
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
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RTOS Kernel
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
8
Task• A task is basic unit of execution
in RTOS. • RTOS scheduler needs to be
deterministic ~ O(1) or O(n). • Scheduling policies that are
available in a RTOS are:– Clock driven– Priority driven
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
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Task Control Block
.
.
TID
SAVED_TASK_STATE
Resource 1 (signals)
Resource 2 (events)
Resource 3 (shared memory)
System Variables
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
10
Memory• Memory is premium in
environments where RTOS work.• Supports Virtual Memory (MMU:
Memory Management Unit) and Memory Protection (MPU) models.
• User space and Kernel space memory.
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
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Virtual Memory Concept
Physical Address Virtual AddressM
.
.
.
.
.
PHY1 VIRT1
PHY2 VIRT2
PHY3 VIRT3
PHY4 VIRT4
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
12
Timer• Timer is SW entity derived from
hardware clock.• Timer provides mechanism to
introduce task-delays and/or to help synchronize and provide time off-course.
• Watchdog Timers, Programmable Timers
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
13
Inter-Process Com.• Most of the time tasks cannot
run in isolation. They require to talk to each other.
• Synchronization, Protection and Sharing are goals of IPC.
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.
14
Device DriverClient Drivers
Protocol Layers
Host Controller Drivers
Hardware
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.