rtos ans soc

8/13/2019 Rtos Ans Soc

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Real Time Operating Systemfor SoC

Department of Computer andInformation Science

National Chiao Tung University


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OverviewMotivationCharacteristics of a Real Time OperatingSystem (RTOS)Components of an RTOSCase Study: VxWorks/pSOS, QNX, OSE,WinCE, Nucleus, eCos, Embedded LinuxConcluding Remarks


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MotivationSoC CPU + ASIC + Software

CPU/ASIC

Operating System

Middleware

Applications

Monitoring, Control,

Remote Management,Consumer Devices

Databases, Graphics, Java

Linux, VxWorks, others...

PPC, 68k, MIPS, ARM,x86, etc.


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An Example: Bluetooth

Baseband


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Software for Bluetooth

Baseband Controller

Radio Transceiver

Link Control

API

L2CAP

SDPRFCOMM

Link Manager

Host ApplicationGSM/UMTS etc

Bluetooth Adviser WDP

WAP

HCI Router

ARM 7TDMI

Lyra/Vega

Link Control/HCI/UART

Management SW


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Real Time OS A RTOS is an abstraction from hardware and

software programmingShorter development timeLess porting effortsBetter reusability

Choosing a RTOS is importantHigh efforts when porting to a different OSThe chosen OS may have a high impact on theamount of resources needed


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Characteristics of a RTOSSingle/Multi-platform OS

Lyra: x86, ARM, MIPS

MultitaskingPriority

Real-timeSoft and hard real time requirements

Variants of RTOS


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Real Time Real -time does not mean speed , butkeeping deadlines Overall deterministic behaviorGuaranteed typically short response/reaction times


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Soft and Hard Real Time

RequirementsSoft real-time requirements:

Breaking the time limit is unwanted, but isnot immediately critical Multimedia Streaming

Hard real-time requirementsBreaking the limit is always seen as afundamental failure Nuclear Power Plant Controller


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Variants of RTOSPure real time OS

Hardware

RTOS

RT-Application


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Pure Real Time OSEspecially designed for real-timerequirements

Completely real-time compliantOften usable for simple architecture Advantage: no or little overhead

Computing power, memory

Disadvantage: limited functionalityExample: eCos, Nucleus, pSOS, VxWork, QNX,OSE, Lyra


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OS Real-Time ExtensionsExtension of an OS by real-time componentsCooperation between RT- and non-RT parts

Advantages: rich functionalityDisadvantage:

No general real-time ability

Computing and memory resourcesExample: RT-Linux, Solaris, Windows NT


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OS Real-Time Extensions

Hardware

Standard OS

RT Applications

RTextension

Applications


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Components of a RTOSProcess(task) managementSchedulerSynchronization mechanism

Interprocess communication (IPC)Semaphores

Memory managementInterrupt service mechanism

I/O managementHardware abstraction layerDevelopment Environments Communication subsystems (Option)Board Su ort Packa es BSP


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Situation of the RTOS Market A vast of RTOS on the market:

Nucleus Plus, OSE, Virtuoso, ThreadX,WinCE, AMX, RTX, LynxOS, VRTX, uC/OS II,OS-9, On Time, VxWork, pSOS, EPOC,eCos

Proprietary OSs Lyra/Vega


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VxWorks/pSOSManufacturer: WindRiver System

Largest player on the market Application examples: HP laser printers, MarsProbe pathfinder, Sony Walkman, digital camera,Internet switch and routers,

CharacteristicsSupport many architecturesTool: TornadoNo memory protection by OSOS ROM size scalable from 80KB to 500KBRAM requirements at least 50KB License + royalty + professional service


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pSOS


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QNXManufacturer : QNX Software Systems Ltd(Canada)

Support many 32-bits architectures: x86, MIPS,PPC, ARM,

Applications: medical technology, automotivetechnology,

Characteristics: Microkernel architectureFull MMU supportGUI supportLicense + royalty Free for non-commercial use


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QNX


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OSEManufacturer: Enea Data (Sweden)Enea has a long tradition in the embedded areaClimber of the last two yearsMain applications: Telecomm (Ericsson, Nokia)

Characteristics:Different kernels for different application areas

The smallest kernel needs only 6 functionsPrinciple of the kernel : message-passingGood connection to the SDL tool chain


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NucleusManufacturer: Accelerated Technology

Application: wireless equipments(handsets), internet access devicesCharacteristics

Source code license + no royalty

Small memory footprint and CPU overheads


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eCosManufacturer : red hat (Cygnus)

Applications : wireless applications,

internet access, embedded applicationsCharacteristics

Open source (GNU license)Implemented in C++ Embedded configurable RTOSMemory footprint from 10s KB to 100s KB


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eCos configuration tool


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Windows CEManufacturer: Microsoft

Application areas: PDA, Industrial embedded

systems, game consolesCharacteristics

Win32 APIOwn tool chain (Visual Studio)For most well-known 32 bit platforms with MMUTypical memory requirements : a few MBs Relative high royalty


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Windows CEShells Internet Explorer Remote Connectivity

Microsoft Programming InterfacesWin32, COM, MFC, ATL, ... Communication Interfaces(Winsock, RAS, TAPI, network)

Kernel

OAL

GWEObject Store

(File Systems)

Native & StreamInterface Drivers

OtherDrivers

IrDA TCP/IP

IRMiniport

EthernetMiniport

Unimodem

PPP/SLIP

Serial NDIS


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Embedded LinuxOpen Source

Almost Free

CommunityCode QualityRobust

Brand NameInternet PlatformIBM will invest 1 Billion per year for Linux


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Embedded and Real-Time

Linux Solution ProvidersLynx -- Blue Cat LinuxMontaVista -- Hard Hat Linux

Lineo -- Embedix LinuxFSMLabs -- RTLinuxZentropix -RealTime Linux

Coollogic -- On-Channel LinuxRedhatIBM


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A Typical Embedded Linux

Embedded Linux OS

GTK+ & GDK GUIJavaVM

Multi-Language SDK DDK GW32

Browser ICAPIMPocketWord

E-mail MP3ICQ

XC Screen Phone &

Web Pad

PDA WBT


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Screen Phone &

Web Pad

WBT

Embedded Linux OS(500 k bytes)

GW32 (800 k bytes)

Browser (1M bytes)

Embedded Linux For Internet Appliances

Embedded Linux OS(500 k bytes)

GW32 (800 k bytes)

ICA (500 k bytes)


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FIC Aqua 3200 WebPAD7.4 DSTN LCDCrusoe 3120 400MHz16M Flash64M RAMEmbedded LinuxNetscape WebBrowser


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Linux PDA - Samsung YOPY4.0 Color TFT LCD206 MHz ARM, 32M

DRAM, 32M FlashMP3 player, Voicerecording, MPEG

ARMLinuxDigital CameraTV (NTSC)


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Lineo EmbedixEmbedix Linux Installertext based

The Shell Ash (much smaller than Bash)

The Kernel Binary

Linux kernel with small number of devicedrivers

The C library (~ 600K)

Reduced Glibc (with tool support)


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The Size of Embedix 1.0The minimum target size for EmbedixLinux on x86

4 MB of RAM and 1MB of ROM, Flash A demo system with v2.0 Linux kernel,web server, shell, DHCP server, CGI scripts,web camera driver4 MB RAM and 1MB Floppy

Lineo Web Browser (HTML 3.2)5 MB of Flash and 16MB of RAM


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Embedix Linux SDK


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Two Classes of Embedded

Linux500KB kernel2MB Flash vs. 16MB Flash

Microbrowser vs. Netscape

4M DRAM vs. 32MB ~ 64MB DRAM


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Linux kernelDesign Focus: Application throughput

Linux use interrupt off critical section

managementLinux kernel is non-preemptableLinux compromises the timely selection of

real-time processes for throughputLinux allow nested interrupts (depends onhardware)


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Current Linux SolutionsDesign application around the problems

Directly use interrupt service routines

Avoid known excessive interrupt offperiods in LinuxIf a process component is required in the

real-time control path, then consideraggregate system loadingUse real-time scheduler instead


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Hybrid KernelRTLiux

run Linux as the idle task

real-time threads are executing in real-timekernelinterrupt off/on operations by Linux are

emulated by lower level kernelcomplex and difficult for applicationdevelopment


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RTLinuxInit Bash

Drivers

Hardware

System calls LinuxKernel

Interruptor

polling

Real timetask

Real timetask

RT-Linux SchedulerI/O

InterruptInterrupt

I/O

Xterm


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Add real-time control to Linux

directlyPreemptive points in Linux kernel

A rate monotonic scheduler (UC Irvine)The KURT program at University ofKansasLinux SRT (soft real -time) project


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MontaVistaMeasure the interrupt off periodsProvide a priority driven real-timeprocess scheduler with fixed and lowoverhead for process creation anddispatch

Measure process preemption delaysDevelop, access and providepreemptable Linux kernel


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EL/IX Delivers The Vision forEmbedded Computing

DevelopmentEnvironment

IncludingGNU Tools

(gcc, gdb, etc.)

Application

Manual or AutoConfiguration

Application Application

EL/IX API

LINUX

eCos or

OtherRTOS

PDA DeeplyEmbedded

User Config API Config

Kernel-levelConfig


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Concluding RemarksHow to select a RTOS for your own SoC ?

What are the requirements of the applications?Which OS features are really necessary?How hard are the real time constraints?Is the OS available for the chosen hardwareplatform? What are the overall cost of using the OSincluding the license fee, tool cost, training androyalty? Consider software issues from verybeginning


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Wireless Multimedia PDA SoCCPUCore

System Bus

LCDcontrol

DMAcontrol

Bridge MemoryController

DRAM

UARTRTC 1

InterruptcontrolGPIO

PowerMgr.

Wireless LANBaseband/MAC RF

Antenna

UART

IO pins

RTC 2

Soundcodec

SpeakerMIC Reset

Reset

DSP

ImageSensor

LCD

Cache


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Embedded Linux with Real

Time ExtensionCadence: Virtual Component Co-design

Hardware/Software Co-design

Mentor Graphics: Seamless for WLAN MACverification Linux Driver(ISS) + MAC (ModelSim)

Intel StrongARM development board /ARM

ASIC Integrator boardEmbedded Linux developmentMPEG 4 Codec

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