Embedded Application

1. Unit 9 Embedded application
Lesson 27 Choosing a Real-Time
Operating System

2. 2023/8/26 2
Lesson 27 Choosing a Real-Time
Operating System
• Backgrounds
• Text tour
• Language in use
– Vocabulary

3. 2023/8/26 3
• Terminology
– Debugger
A debugger or debugging tool is a computer
program that is used to test and debug other
programs (the "target" program).
Backgrounds

4. Stack
• In computer science, a stack is an abstract data type that
serves as a collection of elements, with two principal
operations:
 push, which adds an element to the collection
 pop, which removes the most recently added element that
was not yet removed.
2023/8/26 4

5. 2023/8/26 5
– Source code
In computing, source code is any collection of computer
instructions, possibly with comments, written using a human-
readable programming language, usually as plain text. The source
code of a program is specially designed to facilitate the work of
computer programmers, who specify the actions to be performed
by a computer mostly by writing source code.
– The source code is often transformed by an assembler or compiler
into binary machine code understood by the computer.
Backgrounds

6. Integrated development tool
• An integrated development environment (IDE) is a
software application that provides comprehensive facilities
to computer programmers for software development. An
IDE normally consists of a source code editor, build
automation tools and a debugger.
2023/8/26 6

7. 2023/8/26 7
- Interrupt latency
In computing, interrupt latency is the time that passes from
when an interrupt is generated to when the source of the
interrupt is serviced.
For many operating systems, devices are serviced/operated as soon as
the device's interrupt handler/ISR is executed.
Backgrounds

8. 2023/8/26 8
Text tour
• Outline
– Introduction (para.1, 2)
– Characteristics of an RTOS (para.3-8)
– Selection process (para.9-12)

9. 2023/8/26 9
Introduction
• The term "real time" means the computer problem for which a late
answer is as bad as a wrong one.
• A real-time system has been described as one which "controls an
environment by receiving data, processing them and returning the
results sufficiently quickly to affect the environment at that time".
• The term "real-time" is also used in simulation to mean that the
simulation's clock runs at the same speed as a real clock and in process
control and enterprise systems to mean "without significant delay".
• Designers of real-time embedded systems spends large portion of time
• Worst-case performance
A. Command & Interrupt signal
B. Interrupt latency
C. Triggering the Breaking Mechanism

10. 2023/8/26 10

11. 2023/8/26 11
Characteristics of an RTOS
• To earn the distinctive title " RTOS ", an operating system
should…
– be deterministic (calculable i.e. vendors must publish
datasheets)
– have guaranteed worst-case interrupt latency
– have guaranteed context-switch times (i.e. the amount of
time required to perform a context switch.)
**context switch is the process of storing and restoring the
state of a process or thread so that execution can be resumed
from the same point at a later time.

12. 2023/8/26 12

13. 2023/8/26 13
Selection process
• A wide variety of OSs are available to suit most projects
and pocketbooks.
– at the lower end
• a basic preemptive(automatic) scheduler
• a few other key system calls
– at the higher end
• the basic scheduler
• a lot of functionality

14. 2023/8/26 14

15. 2023/8/26 15
Selection process
• It can be difficult to decide
– Try putting your processor, real-time performance and
budgetary requirements first.
– Then contact the vendors for more detailed technical
information.
• Decision based on compatibility with choice of
cross-compiler, debugger and other development
tools.
• Decide what additional features are most important
for your project.

16. 2023/8/26 16
• Vocabulary
– Suffice execution source
Language in use

17. 2023/8/26 17
Vocabulary

18. 2023/8/26 18
Suffice in dictionary
• To meet present needs or requirements; be sufficient:
– These rations will suffice until next week.
• To be equal to a specified task; be capable:
– No words will suffice to convey my grief.

19. 2023/8/26 19
Suffice in text
• Average or expected-case analysis simply will not
suffice.

20. 2023/8/26 20
Suffice in use
• suffice for
• suffice it to say that...

21. 2023/8/26 21
Execution in dictionary
• The act of executing something.
• The state of being executed.
• The manner, style or result of performance:
– The plan was sound; its execution, faulty.
• The act or an instance of putting to death or being put to
death as a lawful penalty.

22. 2023/8/26 22
Execution in text
• An operating system is said to be deterministic if the
worst-case execution time of each of its system calls is
calculable.

23. 2023/8/26 23
Execution in use
• program execution
• step execution
• execution of contract

24. 2023/8/26 24
Source in dictionary
• The point at which something springs into being or from
which it derives or is obtained.
• The point of origin, such as a spring, of a stream or river.
• One that causes, creates, or initiates; a maker.

25. 2023/8/26 25
Source in text
• Those at the lower end of the spectrum offer just a basic
preemptive scheduler and a few other key system calls.
These operating systems are usually inexpensive, come
with source code that you can modify, and do not require
payment of any royalties.

26. 2023/8/26 26
Source in use
• capital source
• constant flow source
• constant voltage source
• noise source

27. Thank You
2023/8/26 27