Real Time Operating System for SoC

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Real Time Operating System for SoC

• ???
• Department of Computer and Information Science
• National Chiao Tung University

2
Overview

• Motivation
• Characteristics of a Real Time Operating System
  (RTOS)
• Components of an RTOS
• Case Study VxWorks/pSOS, QNX, OSE, WinCE,
  Nucleus, eCos, Embedded Linux
• Concluding Remarks

3
Motivation

• SoC ? CPU ASIC Software

Monitoring, Control, Remote Management, Consumer
Devices
Applications
Middleware
Databases, Graphics, Java
Operating System
Linux, VxWorks, others...
PPC, 68k, MIPS, ARM, x86, etc.
CPU/ASIC
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An Example Bluetooth Baseband
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Software for Bluetooth
Host Application GSM/UMTS etc
WAP
Management SW
Bluetooth Adviser
WDP
API
SDP
RFCOMM
L2CAP
Link Control/HCI/UART
HCI Router

Link Manager
Lyra/Vega
Link Control
Baseband Controller
ARM 7TDMI
Radio Transceiver
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Real Time OS

• A RTOS is an abstraction from hardware and
  software programming
• Shorter development time
• Less porting efforts
• Better reusability
• Choosing a RTOS is important
• High efforts when porting to a different OS
• The chosen OS may have a high impact on the
  amount of resources needed

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Characteristics of a RTOS

• Single/Multi-platform OS
• Lyra x86, ARM, MIPS
• Multitasking
• Priority
• Real-time
• Soft and hard real time requirements
• Variants of RTOS

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Real Time

• Real-time does not mean speed, but keeping
  deadlines
• Overall deterministic behavior
• Guaranteed typically short response/reaction
  times

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Soft and Hard Real Time Requirements

• Soft real-time requirements
• Breaking the time limit is unwanted, but is not
  immediately critical
• Multimedia Streaming
• Hard real-time requirements
• Breaking the limit is always seen as a
  fundamental failure
• Nuclear Power Plant Controller

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Variants of RTOS

• Pure real time OS

RT-Application
RTOS
Hardware
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Pure Real Time OS

• Especially designed for real-time requirements
• Completely real-time compliant
• Often usable for simple architecture
• Advantage no or little overhead
• Computing power, memory
• Disadvantage limited functionality
• Example eCos, Nucleus, pSOS, VxWork, QNX, OSE,
  Lyra

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OS Real-Time Extensions

• Extension of an OS by real-time components
• Cooperation between RT- and non-RT parts
• Advantages rich functionality
• Disadvantage
• No general real-time ability
• Computing and memory resources
• Example RT-Linux, Solaris, Windows NT

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OS Real-Time Extensions
RT Applications
Applications
Standard OS
RT extension
Hardware
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Components of a RTOS

• Process(task) management
• Scheduler
• Synchronization mechanism
• Interprocess communication (IPC)
• Semaphores
• Memory management
• Interrupt service mechanism
• I/O management
• Hardware abstraction layer
• Development Environments
• Communication subsystems (Option)
• Board Support Packages (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/pSOS

• Manufacturer WindRiver System
• Largest player on the market
• Application examples HP laser printers, Mars
  Probe pathfinder, Sony Walkman, digital camera,
  Internet switch and routers,
• Characteristics
• Support many architectures
• Tool Tornado
• No memory protection by OS
• OS ROM size scalable from 80KB to 500KB
• RAM requirements at least 50KB
• License royalty professional service

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pSOS
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QNX

• Manufacturer QNX Software Systems Ltd (Canada)
• Support many 32-bits architectures x86, MIPS,
  PPC, ARM,
• Applications medical technology, automotive
  technology,
• Characteristics
• Microkernel architecture
• Full MMU support
• GUI support
• License royalty
• Free for non-commercial use

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QNX
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OSE

• Manufacturer Enea Data (Sweden)
• Enea has a long tradition in the embedded area
• Climber of the last two years
• Main applications Telecomm (Ericsson, Nokia)
• Characteristics
• Different kernels for different application areas
• The smallest kernel needs only 6 functions
• Principle of the kernel message-passing
• Good connection to the SDL tool chain

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Nucleus

• Manufacturer Accelerated Technology
• Application wireless equipments (handsets),
  internet access devices
• Characteristics
• Source code license no royalty
• Small memory footprint and CPU overheads

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eCos

• Manufacturer redhat (Cygnus)
• Applications wireless applications, internet
  access, embedded applications
• Characteristics
• Open source (GNU license)
• Implemented in C
• Embedded configurable RTOS
• Memory footprint from 10s KB to 100s KB

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eCos configuration tool
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Windows CE

• Manufacturer Microsoft
• Application areas PDA, Industrial embedded
  systems, game consoles
• Characteristics
• Win32 API
• Own tool chain (Visual Studio)
• For most well-known 32 bit platforms with MMU
• Typical memory requirements a few MBs
• Relative high royalty

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Windows CE
Shells
Internet Explorer
Remote Connectivity
Microsoft Programming Interfaces Win32, COM, MFC,
ATL, ...
Communication Interfaces (Winsock, RAS, TAPI,
network)
Kernel OAL
GWE
Object Store (File Systems)
IrDA
TCP/IP
Unimodem
PPP/SLIP
IR Miniport
Ethernet Miniport
NDIS
Native Stream Interface Drivers
Other Drivers
Serial
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Embedded Linux

• Open Source
• Almost Free
• Community
• Code Quality
• Robust
• Brand Name
• Internet Platform
• IBM will invest 1 Billion per year for Linux

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Embedded and Real-Time Linux Solution Providers

• Lynx -- Blue Cat Linux
• MontaVista -- Hard Hat Linux
• Lineo -- Embedix Linux
• FSMLabs -- RTLinux
• Zentropix -RealTime Linux
• Coollogic -- On-Channel Linux
• Redhat
• IBM

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A Typical Embedded Linux
Embedded Linux OS
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Embedded Linux For Internet Appliances
? Browser (1M bytes)
GW32 (800 k bytes)
Embedded Linux OS(500 k bytes)
ICA (500 k bytes)
GW32 (800 k bytes)
Embedded Linux OS(500 k bytes)
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FIC Aqua 3200 WebPAD

• 7.4 DSTN LCD
• Crusoe 3120 400MHz
• 16M Flash
• 64M RAM
• Embedded Linux
• Netscape Web Browser

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Linux PDA - Samsung YOPY

• 4.0 Color TFT LCD
• 206 MHz ARM, 32M DRAM, 32M Flash
• MP3 player, Voice recording, MPEG
• ARMLinux
• Digital Camera
• TV (NTSC)

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Lineo Embedix

• Embedix Linux Installer
• text based
• The Shell
• Ash (much smaller than Bash)
• The Kernel Binary
• Linux kernel with small number of device drivers
• The C library ( 600K)
• Reduced Glibc (with tool support)

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The Size of Embedix 1.0

• The minimum target size for Embedix Linux 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
  driver
• 4 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 Linux

• 500KB kernel
• 2MB Flash vs. 16MB Flash
• Microbrowser vs. Netscape
• 4M DRAM vs. 32MB 64MB DRAM

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Linux kernel

• Design Focus Application throughput
• Linux use interrupt off critical section
  management
• Linux kernel is non-preemptable
• Linux compromises the timely selection of
  real-time processes for throughput
• Linux allow nested interrupts (depends on
  hardware)

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Current Linux Solutions

• Design application around the problems
• Directly use interrupt service routines
• Avoid known excessive interrupt off periods in
  Linux
• If a process component is required in the
  real-time control path, then consider aggregate
  system loading
• Use real-time scheduler instead

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Hybrid Kernel

• RTLiux
• run Linux as the idle task
• real-time threads are executing in real-time
  kernel
• interrupt off/on operations by Linux are emulated
  by lower level kernel
• complex and difficult for application development

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RTLinux
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Add real-time control to Linux directly

• Preemptive points in Linux kernel
• A rate monotonic scheduler (UC Irvine)
• The KURT program at University of Kansas
• Linux SRT (soft real-time) project

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MontaVista

• Measure the interrupt off periods
• Provide a priority driven real-time process
  scheduler with fixed and low overhead for process
  creation and dispatch
• Measure process preemption delays
• Develop, access and provide preemptable Linux
  kernel

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EL/IX Delivers The Vision for Embedded Computing
Development Environment Including GNU Tools (gcc,
gdb, etc.)
Manual or Auto Configuration
User Config
API Config
EL/IX API
eCos or Other RTOS
Kernel-level Config
LINUX
PDA
Deeply Embedded
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Concluding Remarks

• How 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 hardware
  platform?
• What are the overall cost of using the OS
  including the license fee, tool cost, training
  and royalty?
• Consider software issues from very beginning

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Wireless Multimedia PDA SoC
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Embedded Linux with Real Time Extension

• Cadence Virtual Component Co-design
• Hardware/Software Co-design
• Mentor Graphics Seamless for WLAN MAC
  verification
• Linux Driver(ISS) MAC (ModelSim)
• Intel StrongARM development board /ARM ASIC
  Integrator board
• Embedded Linux development
• MPEG 4 Codec