vxworks and embedded linux.ppt

8/9/2019 vxworks and embedded linux.ppt

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VxWorksVxWorks

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Topics CoveredTopics Covered

What is Real Time Operating System (RTOS)

Standard for RTOS

VxWorks Features as RTOS

Layer Struture

!irokernal Funtions"

!ultitasking

Sheduling

#nterrupt Ser$ie %ode

Shared %ode and Reentrany

#ntertask %ommuniations

&ppliations for VxWorks


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What is Real Time OS (RTOS)What is Real Time OS (RTOS)

RTOS Characteristics

'roessing must e done ithin a time onstraint or thesystem ill fail*

&ll delays in the system ill e ounded+ from the retrie$al of

stored data to the time RTOS finishes the re,uest*

Types of RTOS

-ard RTOS

Soft RTOS


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Standard for RTOSStandard for RTOS

Standard re,uirement for RTOS

'OS#. /001*/ y #SO2#333 hapter*

&synhronous #2O

Semaphore

!essage ,ueues

4ueued signals

Sheduling %loks and timers

!emory management

'OS#. interfaes"


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Layer StructureLayer Structure

Real5Time 3medded &ppliation

6raphis !ultiproessing #nternet

7a$a Support 'OS#. Lirary File System

Wind8et 8etorking

Wind Microkernal%ore OS"


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Schedulin!" One C#$Schedulin!" One C#$

'riority5ased preempti$e sheduling

3ah task has priority (from 0 5 highest to ABB 5loest)* 3ah priority has its on ,ueue*

#f to tasks are in the ready state< a loer priority taskould e pre5empted y one of a higher priority*

Round5roin sheduling

&fter time slie for a task expires< another task ith the

same priority ill exeute during the gi$en time slie*

'reemption loks

These loks pre$ent task ontext sithing< ut do notpre$ent interrupt handling*


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%nterrupt Service Code%nterrupt Service Code

Via interrupts< the system is informed of externale$ents*

#nterrupt Ser$ie Routines (#SRs) run outside anytask ontext*

#nterrupt handling in$ol$es no task ontext sith*

Limitations of #SR"

&ll #SRs share the same stak

#SR has no ontext that an e suspended

%annot take the semaphore< ut an gi$e thesemaphores< releasing any task aiting on them*

%annot perform #2O through dri$ers exept pipe*


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Shared Code and ReentrancyShared Code and Reentrancy

Shared Code5 a single opy of ode exeuted y multipletasks*

Shared %ode must e reentrant* & suroutine is reentrant if asingle opy of the routine an e alled simultaneously fromse$eral task ontexts ithout onflit*

Reentrany Tehni,ues"

9ynami Stak Variales 6loal and Stati Variales 6uarded y Semaphores

Task Variales


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Shared Code and Reentrancy" ContinuedShared Code and Reentrancy" Continued

Task/( )C D**

omFun(my9ata/)

E

TaskA( )C D**

omFun(my9ataA)

E

omFun(your9ata)CE

my9ata/

my9ataA

9ynami Stak Variales

Tasks Task Staks %ommon Funtion


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Shard Code and Reentrancy" ContinuedShard Code and Reentrancy" Continued

6uarded 6loal and Stati Variales

Mutual-exclusionmehanism 5 only one task at a time

an e in a ritial setion of the ode*

Task Variales

Four yte $ariales are added to the task ontextlok (T%@)*


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%ntertask Communications" One C#$%ntertask Communications" One C#$

Shared 9ata

!essage 4ueue

'ipes 5 Virtual #20

8etork #ntertask %ommuniation

Sokets

Remote 'roedure %all

Types of #ntertask %ommuniations"


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%ntertask Communication" Shared &ata%ntertask Communication" Shared &ata

&ess Shar9ata

&ess Shar9ata

Tasks !emory

&ess Shar9ata

Shar9ata

/*

A*

1*


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SemaphoresSemaphores

Semaphore 5 mehanism for mutual exlusion and intertaskommuniation*

@inary Semaphore

Semaphore

a$ailale

TimeOut=

8oWait

Task ispended fortimeOut

Task ont*

Semaphore

taken

8O8O 8O

G3S

Task ont*

Semaphore

not taken

G3S


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Semaphores" ContinuedSemaphores" Continued

#s semaphore is gi$en and no tasks areloked< ount >>

%ounting Semaphore

3$ery time is semaphore is gi$en ount >>

3$ery time is semaphore is taken ount 55

#f ount=0< task that tried to take semaphore is loked #f semaphore is gi$en and task is loked< task isunloked

Speial Semaphore Option (8ot in 'OS#.)

Timeout

Time the task is illing to ait (time in tiks) in pended

state* #f time H timeout< 3RROR ours*


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%ntertask Communication" essa!e%ntertask Communication" essa!e'ueue'ueue

&llos a $ariale numer of messages to e ,ueued

&ny task or #SR an send a message to a ,ueue*

!ultiple tasks an send and reei$e from the samemessage ,ueue*

Timeout 'arameter"

Send message" ho long to ait for uffer spae

to plae message*

Reei$e message" ho long to ait to otainmessage*


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pplications for VxWorkspplications for VxWorks

Flight simulators

Radio and optial telesopes

8a$igation systems

9eep sea instrumentation

Traffi ontrol systems

!odems

D any systems here rigid time re,uirement ha$e eenplaed on the operation of a proessor or the flo of the data*

Some usage of RTOS

'rinters

9igital ameras

-and5held omputingde$ies

Routers< sithes< andother netork de$ies


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Commercial m*edded LinuxCommercial m*edded Linux

+eo,are +eoLinux

Red -at derived for informationappliances

#alm#alm Tynux%nternet appliuance and multimedia

Red -at m*edded Linux

!eneral purpose em*edded solution

RedSonic Red.%ce Linux

runs from &iskonChip orCompact/lash


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Commercial m*edded LinuxCommercial m*edded Linux

Rid!eRun &S# Linux

for multimedia" ,ireless" RT on &S#

TimeSys Linux 0#L

lo, latency enhanced kernelTuxia TST

distro tar!ets %nternet appliances

Vital Systems vLinuxfor R *ased em*edded apps


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Open Source m*edded LinuxOpen Source m*edded Linux

m*edded &e*ian #ro1ect

convert &e*ian to an em*edded OS

TLinux

for #C234 S5C6s

uCLinux

for microprocessors that don6t have

uLinux (muLinux)distro fits on a sin!le floppy


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Commercial Linux RTOSCommercial Linux RTOS

/SLa*s . Open RT Linux

Lineo . m*edix Realtime

LynuxWorks . 5lueCat RT

ontaVista Soft,are . Real Timextensions

R&Sonic . R&%C Linux

TimeSys . Linux7Real.Time


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Open Source Linux RTOSOpen Source Linux RTOS

RT Linux . real time extension *ased onRTLinux

8$RT . event schedules ,ith 23us resolution

Linux.SRT . for soft real time apps likemultimedia

'linux . provides 'uality of Service !uarantees

RT% . 9hard: Real Time pplication %nterface


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RTLinuxRTLinux

9hard real.time: mini operatin! system

runs Linux as it6s lo,est priority executionthread

Linux thread completely preempti*le

Real time threads and interrupt handlersnever delayed *y non.realtime operations

Supports user level pro!rammin!

iniRTL implementation fits on a floppy


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What6s so special a*out Linux;What6s so special a*out Linux;

ultiple choices vs< sole source

Source code freely availa*le

Ro*ust and relia*le

odular" confi!ura*le" scala*le

Super* support for net,orkin!and %nternet

+o runtime licenses

Lar!e pool of skilled developers


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What6s so special a*out Linux;What6s so special a*out Linux;


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What6s special a*out Open Source;What6s special a*out Open Source;

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vxworks and embedded linux.ppt