embedded Operating system application lecture notes for graduate students

1. Embedded Operating
Systems and
Application
Lirong Chen
741091483@qq.com

2. Introduction of
Embedded Systems and
Embedded Operating Systems
1 The concept of embedded systems
2 The concept of real-time systems
3 Overview of embedded operating systems

3. Automotive electronics control systems
motor
controller
lamp

4. In an automotive, internal communication buses connect ECUs of different
application domains, such as the powertrain domain, the chassis and safety
domain, the infotainment domain, and the comfort domain.

5. n Anti-lock Braking System (ABS)
• Real time and
• Safety-related!
layered software
architecture of an ECU

6. ○ flight
control
A D
B C
○ fire
control
○ missile
launching
○ ……
Av i o n i c s

7. Radar
Weapons
Nav
Sensors
Weapon
Management Data Links
Stick,
Throttle…
Actuators
Mission
Computing
Vehicle
Management

9. communication base stations
Smart phones
Intelligent electric meters
Smart refrigerators
Cash registers
Industrial robots
Medical instruments
UAV(unmanned aerial
vehicle)

10. • An embedded system is a computer system contained within some larger
device or product with the intent purpose of providing monitoring, and
control services to that device.
• Any sort of device which includes a programmable computer but itself is
not intended to be a general-purpose computer.
• IEEE: “Device used to control，monitor，or assist the operation of
equipment，machinery or plants”.
• Embedded Systems are applications oriented systems, based on computer
technologies, with tailorable hardware and software. They are special
purpose computer systems satisfying strict requirements such as
functionalities, reliability, cost, size and power consumption.

11. • Embedded systems are combination of advanced computer technologies,
semiconductor technologies and electronic technologies, they have
concrete applications of diverse domains.
• Physically, embedded systems range from portable devices such as
digital watches and MP3 players, to large stationary installations like
traffic lights, factory controllers, or the systems controlling nuclear
power plants.
• Complexity varies from low, with a single microcontroller chip, to
very high with multiple units, peripherals and networks mounted
inside a large chassis or enclosure.

12. Anti-lock brakes
Auto-focus cameras
Automatic teller
machines
Automatic toll systems
Automatic transmission
Avionic systems
Battery chargers
Camcorders
Cell phones
Cell-phone base stations
Cordless phones
Cruise control
Curbside check-in
systems
Digital cameras
Disk drives
Electronic card readers
Electronic instruments
Electronic toys/games
Factory control
Fax machines
Fingerprint identifiers
Home security systems
Life-support systems
Medical testing systems
Modems
MPEG decoders
Network cards
Network switches/routers
On-board navigation
Pagers
Photocopiers
Point-of-sale systems
Portable video games
Printers
Satellite phones
Scanners
Smart ovens/dishwashers
Speech recognizers
Stereo systems
Teleconferencing systems
Televisions
Temperature controllers
Theft tracking systems
TV set-top boxes
VCR’s, DVD players
Video game consoles
Video phones
Washers and dryers

13. Information
appliance
Mobile
terminals
Communica
tion
equipment
Automotive
electronics
Industrial
control
systems
Medical
instruments
……

14. n Pervasive Computing(Ubiquitous Computing): the trend towards
increasingly ubiquitous, connected computing devices in the environment,
a trend being brought about by a convergence of advanced electronic
(particularly wireless) technologies and the Internet.
• Ubiquitous Computing (Mark Weiser, Xerox PARC 1988)
• Calm Computing (John Brown, Xerox PARC 1996)
• Universal Computing (James Landay, Berkeley 1998)
• Invisible Computing (G. Barriello, UoWashington 1999)
• Context Based Computing (Berkeley/IBM 1999)
• Hidden Computing (Toshiba 1999)
• Pervasive Computing (Academia, IBM 1999, SAP 2000)
• Post PC Computing (common sense)
• Ambient Intelligence (European Commission, FP5)
• Everyday Computing (Georgia Tech, 2000)
• Sentient Computing (AT&T, 2002)
• Amorphous Computing (DARPA, 2002)…
Wearable Computing

16. 3rd party application
suppliers: information,
navigation,
entertainment…
4S shops: vehicle
maintenance, rescue,
remote diagnostic,
update…
OEMs:
information
collection, remote
update…
Intelligent
transportation: eCall,
transportation
management, road side
unit management…
ICV:
Intelligent
Connected
Vehicles
ITS:
Intelligent
Transportation
System

17. • Specialized and optimized for specific
application
• Support many kinds of processor
architectures
• High efficiency
• Embedded operating systems usually
supports many kinds of processors, and
are tailorable, light-weighted, real-time
and reliable, and can be solidified
• Special tools and methods are needed to
develop embedded systems
Host system target system
Cross development of embedded software

18. Real-time
Memory constraint
Low power consumption
Cost sensitive
High dependability/reliability
execution time of OS services

19. High dependability of embedded systems
• Reliability R(t) = probability of system working correctly
provided that is was working at t=0
• Maintainability M(d) = probability of system working
correctly d time units after error occurred.
• Availability: probability of system working at time t
• Safety: no harm to be caused
• Security: confidential and authentic communication

21. functional
safety

22. functional
safety

24. a typical embedded OS:
~4KLOC (lines of code)
EAL7: ~$1,000 per LOC
cost: ~$4Million

25. MILS SEPARATION KERNEL
Application
Middleware
TS
(SL)
Processor
Application
Middleware
U
(SL)
Application
Middleware
C
(SL)
Application
Middleware
S
(SL)
Minimal
Middleware
Minimal
Runtime
TS/S
(MLS)
Guest OS Guest OS Guest OS Guest OS
Linux Linux LynxOS LynxOS
LynuxWorks Lynx Secure
Padded Cell
Linux
Padded Cell
Linux
POSIX
Runtime
POSIX
Runtime
Green Hills INTEGRITY
VxWorks VxWorks VxWorks VxWorks
Wind River VxWorks MILS
MILS Separation Kernel
A MILS Workstation?
Mac OS
John Rushby

26. Powerful two-level time and space schedulers: implements a strict two-level scheduler for
maximum separation, performance, and scalability. The module operating system (MOS)
operates in kernel space and schedules MMU-protected partitions, on a predefined time basis.
Inside each partition the partition-level operating system (POS) schedules tasks on a priority-
preemptive basis, using VxWorks, ARINC, POSIX, or other API. This robust scheduling and
separation environment enables the deployment of different safety certification levels on a
single instance of silicon and deterministic performance when increasing the number of virtual
application partitions.
module operating
system (MOS)
partition-level
operating systems (POS)

27. Based on ARINC653

28. • The relationship of embedded systems and real-
time systems
• Embedded software usually can be executed directly from flash memory
or loaded into RAM，and can be rapidly booted.
§ For real-time systems, right answers arriving too late are wrong.

29. • Real-time means“immediately”,“on time”
• Real-time systems need to response to external events in
limited time.
• “Any system where a timely response by the computer to external
stimuli is vital is a Real-Time System”.
• Just functionally working is NOT enough!
• Real-time control systems and real-time information processing
systems are both called real-time systems

30. • The response times range from
microseconds to milliseconds
strong
Real-time
systems
• The response time are at the
level of several seconds
Normal
real-time
systems
• The response times are even
longer, range from tens of
seconds(or minutes) to longer
Weak
real-time
systems
automotive
braking
control
system
traffic lights
stock
system

31. 100ns
1μs
10μs
100μs
1ms
10ms
100ms
1s
Speech and
Audio
systems
Process
simulation and
network control
Flight
simulation
Robot
controllers
Telemetry control
& science analysis
Process
control
systems
and
Industrial
Automation
Medical Diagnosis
and lab automation
Fire alarm systems
Time
Constrains
slower
faster
Applications

32. • Have strict response time limit,
which must be satisfied,
otherwise the system will
breakdown or lead to fatal error
Hard
real-time
systems
• If the response time does not
satisfy the limit, the system will
not collapse, nor lead to fatal
error
Soft
real-time
systems

33. nAre operating systems necessarily needed by embedded
real-time systems?
Polling
system
Fore/back-
ground
system
Single-
processor
Multitask
system
Multi-
processor
multitask
system

35. background
foreground
Higher priorities

37. For a complex embedded real-time
system, when:
• It’s difficult to fulfill the functionalities
of the system with the software
structure of interrupt processing
routines plus a background program,
especially when the system has
requirements of real-time and high
dependency
• There exit some unrelated tasks to be
processed at the same time
Then we need a multitask system!
Background:
Multi-tasks
Foreground:
ISRs
an extension of fore/back-ground system!

38. Features:
• S e v e r a l s e q u e n t i a l p r o g r a m s e x e c u t e
concurrently.
• On the macro point of view, all programs run at
the same time, each executes on its own
machine(CPU+ other hardware resources).
• In fact, they share the same CPU and other
hardware components. Thus, a RTOS is needed
to manage these shared devices and data.
• Each program is an infinite loop, waits for
dedicated input data, and does corresponding
processing.
• This is a programming model dividing the whole
system into some simpler and cooperating
modules.

39. qadvantages
v Decompose a system into relatively independent threads, thus
decrease the complexity of the system
v Guarantee the real-time property of the system
v It’s easier to maintain the system
qdisadvantages
v Some new software design methods must be adopted
v mechanisms such as threads coordination, synchronization and
communication must be provided
v Mutual exclusion mechanism must be used to protect shared
resources
v Competence between threads can not be avoided
v It’s necessary to use RTOSs，which increase the system overhead

40. Embedded operating systems have functionalities similar with normal operating
systems, meanwhile, they have features of embedded software：
• Real-time
• Configurable, tailorable
• Independent Board Support Packages which can be modified
• Have dedicated versions for special CPU architectures
• ARM MIPS PowerPC Super H X86 RISC 5......
• Integrated cross tools are used to develop applications based on embedded
operating systems

41. OS name description
Corporation /
organization
uC/OS
Famous open source embedded real-
time OS
Micriμm
OSEK OS
Real-time OS used in automotive
industry
OSEK
organization
AUTOSAR OS
Real-time OS used in automotive
industry
AUTOSAR
organization
VxWorks
Famous commercial embedded OS,
commonly used in many embedded
systems
Wind River
QNX OS
Famous real-time embedded OS, now
commonly used in telematics boxes on
modern automotive
QNX
INTEGRITY
Famous commercial real-time
embedded OS
Green Hills
Nucleus Famous real-time embedded OS
Accelerated
Technology

42. example: architecture of the QNX operating system

43. The INTEGRITY® RTOS is a
secure, maximum reliability,
real-time operating system
intended for use in mission
critical embedded systems.
The velOSity™ RTOS is
small and fast—making it
perfect for high volume,
cost-sensitive, and deeply
embedded applications.
The INTEGRITY-178B RTOS is securely partitioned, making
it ideal for demanding safety critical applications that contain
multiple programs with different levels of safety criticality—all
executing on a single processor.
The royalty-free µ-velOSity real-
time microkernel is the smallest of
Green Hills Software’s family of
operating systems.

44. • Android
• iOS
• Embedded Linux
IVI(In-Vehicle
Infotainment)

45. • Give 2~3 descriptions about the concept of embedded systems
• Name out some application domains of embedded systems
• What is “pervasive computing”?
• List out the main features of embedded systems
• What are the main non-functional constraints of embedded systems?
• The concept of real-time system and its relationship with embedded system
• The categories of real-time systems when classified by response time
• The categories of real-time systems when classified by the deterministic attribute
• The definition of hard real-time system
• Does embedded real-time system (ERTS) necessarily need OS? Why?
• According to the software architecture, what categories can embedded systems be classified into?
• The structure of fore/back-ground systems.
• What indicators are used for the performance of fore/back-ground systems?
• The main features of multi-task systems
• The advantages and disadvantages of multi-task systems
• Features of embedded OS