Introduction to RTOS

1. 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. 2
Smart Device Structure
8. Introduction to IoT
9. Smart Device RF & Antennas
10. Introduction to RTOS
11. Introduction to Bluetooth

3. 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.

4. 4
Types of RTOS

5. 5
Structure of RTOS
Custom-Hardware
RTOS-kernel
Applications
BSP
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.

6. 6
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.

7. 7
RTOS Kernel
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.

8. 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.

9. 9
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. 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.

11. 11
Virtual Memory Concept
Physical Address Virtual AddressM
.
.
.
.
.
PHY1 VIRT1
PHY2 VIRT2
PHY3 VIRT3
PHY4 VIRT4
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.

12. 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. 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. 14
Device Driver
Client Drivers
Protocol Layers
Host Controller Drivers
Hardware
□ Courtesy to Mishra & Chawla, RTOS Design & Implementation, slideshare.